ZSE Aviation Forecast Discussions

779 FXUS66 KSEW 261010 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 310 AM PDT Wed Mar 26 2025 .SYNOPSIS...A strong storm system will lift a front across western Washington on Wednesday, bringing in a chance for widespread thunderstorms with severe thunderstorms possible. A cold front Thursday will bring cooler temperatures while maintaining unsettled conditions. Active weather is favored to continue through the period with near-normal temperatures. && .SHORT TERM /TODAY THROUGH FRIDAY/...The main story today is the potential for severe thunderstorms across western WA this afternoon and evening with a warm, moist and unstable air mass over the region. We`re under strong, diffluent flow with a deep/stacked system rotating offshore. Per the HREF model, showers/thunderstorms will initiate over western OR around 1-2pm then spread northward into western WA through the rest of the afternoon and evening (as a cold front moves in). Timing for the Seattle metro area is around 5-7 pm. Steep lapse rates and mean CAPE values exceeding 1,000 J/kg support strong updrafts across the area with supercells expected. The Storm Prediction Center has a Slight Risk of severe thunderstorms west of the Cascades. The main threats include large hail (up to 2" in diameter), damaging wind (58 mph or greater) and (to a lesser extent) brief tornadoes. Other threats include cloud-to-ground lightning and brief heavy downpours. Severe weather threats start to diminish this evening (after 9 pm) as a shortwave ejects north into B.C. All in all, a very active day anticipated with multiple weather threats not too common for the NW. The upper low continues to spin offshore on Thursday, keeping the weather showery across western WA. There is still a threat of thunderstorms across the area but we`re not expecting severe thunderstorm development. It`ll be breezy along the coast and north interior with S/SE gusts to 30-40 mph. Friday will be cooler (back to normal) as the upper low nudges inland. The air mass remains moist with additional showers expected. 33 .LONG TERM /SATURDAY THROUGH TUESDAY/...Upper level troughing over the Pac NW will maintain showers as we move toward the end of the week. Temperatures will be back to our seasonal averages with highs in the lower to mid 50s. A weak ridge brings a short break in the weather moving into Sunday. More wet and windy weather is headed our way next week as low pressure shifts inland. 33 && .AVIATION...Southwesterly flow aloft turning southerly as a low pressure system approaches western Washington. Conditions starting to deteriorate early this morning to IFR/LIFR as abundant low- level moisture combined with a lingering inversion layer has produced low clouds/fog across the area terminals. Lowered conditions will continue through the morning hours before gradually improving to VFR as a cold front approaches the region, mixing out the fog. As this front crosses over western Washington, models continue to remain consistent in thunderstorm activity Wednesday afternoon and evening (23z-04z). Within these thunderstorms and showers, conditions will likely drop to widespread MVFR, with the potential for brief IFR in heavier rain showers and lower visibilities. The main threats with these thunderstorms are frequent lightning, gusty and erratic winds, Dial, and brief periods of heavy rain for much of the area. During these threats, conditions can dramatically change, from VFR, to IFR quickly. Showers will remain through the overnight period, but conditions should balance out at VFR through Thursday morning. KSEA...VFR early this morning with northerly winds around 5 to 10 knots. Guidance continues to show high probabilities (60%) of fog developing early this morning (11z-14z) with IFR/LIFR conditions. Visibilities could be down to a mile or lower. Conditions will improve to VFR later into the morning into the afternoon, before thunderstorms start to develop across the area. The main time frame where thunderstorm activity will peak at the terminal is 00z-04z. The main threats will be hail, gusty erratic winds, frequent lightning, and heavy downpours at times. Within these conditions, conditions can and will likely fluctuate from VFR/MVFR/IFR during the aforementioned time period. VFR will resume late tonight into Thursday morning Outside of thunderstorms, winds will turn southerly and remain 5 to 10 knots. Mazurkiewicz && .MARINE...Surface high pressure has shifted inland this morning making room for an incoming low pressure system offshore and a strong cold front associated with it. An inversion this morning could produce fog over the inland waters, decreasing visibilities down to 1SM. A cold front will push through the waters this evening into Thursday morning. Behind the front, southerly winds will increase over the coastal waters. Initially the strength of these winds will be at small craft (20 to 30 kts), then consistently strengthen to gale by Thursday afternoon. Most of the gale strength will come with the gusts, with guidance suggesting a 60-70% chance of frequent 35 to 40 kt winds across the coastal waters through Thursday evening. Elsewhere, can expect small craft advisory strength winds over the interior waters (Eastern Strait, Admiralty Inlet, Northern Interior). Coastal seas through tonight generally remaining 6 to 8 feet, slowly building upwards to 15 to 20 feet possible by late Thursday. Seas will begin to subside through Friday, decreasing to below 10 feet by Saturday. Active weather will continue the end of the weekend into the first half of next week, where additional systems look to bring another round of elevated winds and seas. Mazurkiewicz && .HYDROLOGY...A storm system Wednesday will bring showers and thunderstorms to the region, with potential for locally heavy rainfall at times in stronger activity. However, due to the convective and spotty nature of this precipitation, most area rivers are expected to stay below Flood Stage. Precipitation will continue throughout the week as active weather continues, but is not expected to cause significant rises to area rivers. The exception is the Skokomish River, where heavy showers mid- week are favored to bring the Skokomish into Flood Stage by late Thursday where it will likely remain through early Saturday. The latest forecast has the river peaking into Moderate Flood Stage, but large uncertainty exists over the amount of precipitation over the basin. Conditions will continue to be closely monitored. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 11 PM this evening to 11 AM PDT Thursday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Gale Warning from 11 AM Thursday to 5 AM PDT Friday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. && $$

461 FXUS66 KPQR 260022 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 522 PM PDT Tue Mar 25 2025 .SYNOPSIS...Dry conditions continue overnight. Wednesday begins warm but will become active during the afternoon with showers and possibly severe thunderstorms during the afternoon and evening hours. Active weather will continue through the remainder of the week and into the start of the upcoming week. So, expect rather typical spring weather with rain showers, Cascade snow and near normal temperatures. && .SHORT TERM...Now through Thursday... Now through Thursday Night...Dry and unseasonably warm warm conditions continue through the overnight. Temps throughout the Willamette Valley are in the low to mid 70s while locations along the coast are in the 60s. Temps will continue to rise through the afternoon with record highs for today still within reach for many locations. Currently, the standing records for various locations across our forecast area are as follows: Astoria: 69/1934 Vancouver: 72/1997 Downtown Portland: 75/1966 Portland Airport: 74/1966 Hillsboro: 73/1997 Mcminnville: 72/1966 Salem: 72/1997 Eugene: 73/1997 Wednesday will begin mostly dry and warm for the area but a large area of low pressure over the northeast Pacific will see an embedded shortwave round the base of the trough, passing over the PacNW. This shortwave will have a substantial negative tilt to it, leading to a diffluent upper level pattern favorable for strong to severe thunderstorms. Confidence remains high in the moisture component of this system with PWAT values peaking between 0.8-1.2 inches Wednesday afternoon and evening. Confidence in instability has increased over the last 24 hours with model consensus showing at least partial clearing during the late morning to afternoon hours across w WA and NW OR. A capping inversion is expected to be in place to start Wednesday morning which will initially keep convection at bay but as surface temps warm, this cap will erode and allow for convective initiation. CIN values in the morning are expected to be between 100-200 J/kg, dropping below 50 J/kg in the afternoon. SBCAPE during the afternoon could reach the 1000-2000 J/kg range or higher based on CAM soundings. The ECMWF Extreme Forecast Index notable depicts CAPE values maxing out local percentiles relative to the 20 year average, so potential for an unusual or rare event is very much in the cards. Other components for severe weather are also expected to influence this event. Effective shear across the region is expected to be healthy, generally 30-50 kts with SW surface winds backing to the south at 700 mb leading to a bit of direction shear. Helicity values between 100-150 m2/s2 will be possible and would help in the development of supercells, or spinning thunderstorms. Parameters to note are the low and mid level lapse rates which are rather steep for the PacNW at 5-8 C/km in the low levels and 7-9 C/km which will aid in supporting increasing CAPE. DCAPE, or downdraft CAPE in the 500-700 J/kg range indicates potential for strong damaging winds within thunderstorms which can be realized when the core of a thunderstorm collapses. Confidence in severe thunderstorms has increased in the last 24 hours, prompting an upgrade in the SPC convective outlook from Marginal to Slight risk from the I-5 corridor to the Cascade crest. The main threat is large, damaging hail as SPC has added a 15% hatched area for large hail +2.0 inches in diameter. A low tornado risk has also been added to the area, though the overall environment may not be favorable for tornado development. The rarity of the environmental ingredients over the area warrants this addition due to lack of previous events and overall heightened threat for severe weather. According to records dating back to 2002, this is the first day 2 slight risk issued in March west of the Rockies. Make sure you have a way of recieving NWS alerts and have an action plan in case you are caught in a severe thunderstorm warning. Thursday, will maintain cooler weather and while the very favorable south/southwest flow pattern will persist. Current conditions are looking to be less favorable for thunderstorm development. Model soundings show CAPE values plummeting towards around 100 J/kg along with 15 J/kg of CIN. This means that the overall environmental conditions within the atmosphere are not favorable for thunderstorm development. Still, will continue to monitor as this could change. Winds will also potentially be of concern with a 20-40% probability for southerly gusts up to 45 mph for the Willamette Valley with the highest probability around Salem. The coast has a 30-40% probability for southerly gusts up to 58 mph. We will continue to monitor the forecast as these gusts are very close to Wind Advisory or Wind Warning thresholds. -Batz/42 .LONG TERM...Friday through Monday night...As the latter part of the week approaches and we press into the start of next week, a generally active pattern will persist. However, temperatures will trend back towards seasonal normals with daytime highs in the 50s and low 60s. Training systems will keep additional rounds of rain showers and Cascade snow in the forecast. /42 && .AVIATION...Much more complicated forecast for the next 24 hours as high pressure and warm temperatures give way to a strong cold front after 18Z Wednesday. Temperatures are generally above normal today which may be impacting air density and creating thermals along runways. In addition, with weak flow at the surface and southerly winds aloft, some gravity waves have formed along the Cascades. Looking at satellite, the edge of the cold front is far enough offshore to be non-impactful, but overnight that will shift. As the cold front makes it`s initial onset, could see some elevated convection (around 20% chance), especially along the coast. Not expecting significant lightning or hail, but cannot rule it out. Within the interior lowlands, clear skies overnight will allow for more radiational cooling. With the moisture available during the day, fog again is possible. Areas most at risk will be around KSLE and KUAO as they currently have some of the higher humidity within the Valley and winds will be southerly. This fog will be a factor moving forward though as the cold front pushes further inland. We are expecting a very active severe weather day and cannot emphasize enough that Wednesday is an abnormal day for the Pacific Northwest in the realm of severe weather. Based on forecast models, there is a moderate chance (40-60%) that thunderstorms with large hail could occur. In addition, based on the vertical nature of the atmosphere with strong turning winds, tornadoes are not out of the question. At this time, confidence is low on exactly where storms will end up, but there is a high probability that they will occur. The period of connectivity will be after 19Z Wednesday. PDX AND APPROACHES...20% chance of patchy fog after 06Z Wednesday. Conditions will clear then turn to very convective in the afternoon. Increasing chances for thunderstorms, and large hail. Outflow winds from storms will be strong with gusts up to 40 kt possible. Tornadoes are not out of the question. -Muessle && .MARINE...High pressure overhead continues to support tranquil conditions across the coastal waters. A relatively warm and humid airmass atop cool ocean waters will see additional periods of marine fog with visibilities below 1 SM, and the Dense Fog Advisory remains in place through 5 AM PDT Wednesday. Wednesday into Thursday, there remains high confidence that a strong area of low pressure will bring much higher winds and seas across the waters. Storm-force winds are likely to occur with this system with wind gusts up to 55 kt expected in the outer waters south of Cape Falcon. Elsewhere north of Cape Falcon and across the inner waters including the Columbia River Bar, gale-force gusts up to 45 kt are likely. Seas will also rapidly increase, becoming steep and hazardous Wednesday night into Thursday with significant wave heights most likely peaking between 20-25 feet. Storm and Gale Warnings have therefore been issued across the waters from Wednesday afternoon through Thursday night. Hazardous seas over 15 ft will likely persist through Friday afternoon while winds diminish into the weekend. -TK/Picard && .BEACH HAZARDS...Beachgoers and those participating in the upcoming razor clam digs should be aware of a moderate risk of sneaker waves most of this week. Be sure to never turn your back to the ocean and keep a close eye on incoming waves, as sneaker waves can catch beachgoers by surprise, sometimes resulting in injury or death. Avoid jetties, large logs, and large rocks. High surf advisory conditions are possible late Thursday into Friday with wave heights potentially exceeding 25 ft, although much of the surf energy will be directed along-shore, possibly limiting surf impacts to area beaches. Lastly, there is a chance of marginal tidal overflow flooding along the south WA coast around high tide early Friday morning. As of right now, the total tide forecast at Toke Point, WA is forecast to each 11.1 feet for an hour or two, just barely meeting our criteria of 11 ft for the issuance of a coastal flooding advisory for tidal overflow. Given how marginal conditions are and the lead time involved, have opted to hold off on issuing a coastal flood advisory. -TK/Picard && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Dense Fog Advisory until 5 AM PDT Wednesday for PZZ210-251>253- 271>273. Small Craft Advisory from 11 AM to 11 PM PDT Wednesday for PZZ210. Gale Warning from 11 PM Wednesday to 5 AM PDT Friday for PZZ210. Small Craft Advisory from 8 AM to 8 PM PDT Wednesday for PZZ251-271. Gale Warning from 8 PM Wednesday to 5 AM PDT Friday for PZZ251- 271. Small Craft Advisory from 8 AM to 2 PM PDT Wednesday for PZZ252-253. Gale Warning from 2 PM Wednesday to 5 AM PDT Friday for PZZ252- 253. Small Craft Advisory from 6 AM to 2 PM PDT Wednesday for PZZ272-273. Gale Warning from 2 PM Wednesday to 8 AM PDT Thursday for PZZ272-273. Storm Warning from 8 AM to 5 PM PDT Thursday for PZZ272-273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

031 FXUS66 KMFR 261047 AFDMFR Area Forecast Discussion National Weather Service Medford OR 347 AM PDT Wed Mar 26 2025 .DISCUSSION...An approaching upper low will send a front towards the area, moving inland late today and tonight. The main impact ahead of this front will be with strong winds developing over portions of the area today (mainly east of the Cascades and into the Shasta and Rogue valleys) and chances for showers and thunderstorms with a low chance for severe thunderstorms in parts of southwest Oregon. Rain moves inland with the front late today and tonight. Then as the low will nears the coast of Oregon on Thursday expect rain (moderate to heavy area areas along the coast), higher level snow and strong winds. Today, temperatures will trend cooler compared to yesterday but will still be above normal today. Ahead of the front, a strong jet aloft will nudge into the area. Additionally, sufficient moisture combined with instability (LIs -2 to -4), CAPE (200 to 800) and steep lapse rates will allow for showers and thunderstorms to develop ahead of the incoming front. Although chances for thunderstorms (10-30%) extend across much of southwest Oregon as well as into Siskiyou and far northern Modoc counties, the best chances for thunderstorms will be across Douglas County, southward into Jackson and extending eastward into northern Klamath County and northern Lake County. Models continue to show thunderstorm and shower activity is likely to initiate west of the Cascades by early afternoon then gradually move northeastward late this afternoon and this evening. The Storm Prediction Center continues to indicate a very low chance (5%) for severe thunderstorms across areas of southwest Oregon with some low chances (15%) for far northeast Douglas County as well as areas to the north. Hail and gusty winds may accompany any storms today. Stronger cells may develop strong, damaging winds and large hail. Additionally, widespread gusty winds are likely to develop across the area this afternoon and evening as winds aloft increase and mix down into lower levels. As the front moves inland this evening and tonight and then the low pressure center approaches inside of the 130 W on Thursday, gusty winds are likely to continue across the area. These strong winds are expected to peak on Thursday. Strongest winds are expected in the Shasta Valley and east of the Cascades as well as over higher mountains. High wind warnings and wind advisories are in effect today into Thursday. Gusty south winds reaching advisory levels are also likely in the southern Rogue Valley today. These winds in the Rogue Valley are expected to decrease tonight but then are likely to increase again Thursday. For areas along the southwest Oregon coast, high winds are likely as the upper low nears the Oregon coast on Thursday. As this low tracks inside of 130 W, models show a lower level jet of 60 to 70 kt moving onshore Thursday morning and afternoon while the surface pressure gradient increases (with a Medford to Arcata surface pressure gradient of -7 to -9). This is an indicator for strong, gusty winds (with gusts of 60 to 70 mph) developing along the coast, mainly from Cape Blanco southward and across headlands. A high wind warning remains in effect for coastal areas on Thursday. Otherwise, rain is expected to move inland as the front pushes onshore late today into tonight, followed by a mix of rain and snow on Thursday as the upper low nears the area. Snow levels will lower from above 8000 feet today to near 4000 to 5500 feet on Thursday. Snow impacts are likely to be mainly light, with some moderate snow impacts possible over higher peaks in western Siskiyou County and locally in the Southern Oregon Cascades. Of note, models indicate weak instability over western portions of the area on Thursday with a low chance (10%) for thunderstorms, mainly across areas west of the Southern Oregon Cascades. On Friday, the low pressure system weakens and and moves inland to the north with an upper trough over the region. Moist westerly flow will allow for numerous showers across southwest Oregon and northern California. Then, a shortwave ridge builds into the area on Saturday, bringing a brief break in activity Saturday and Saturday night. Sunday into early next week, expect a continued active pattern although confidence is low in the details. Overall, expect another front to move into the area Sunday into Monday as a low moves up from the west-southwest. Then additional unsettled weather is likely with an upper low off the coast on Monday, then weakening with a trough over the area Tuesday. && .AVIATION...26/12Z TAFs...Tonight is literally the calm before the storm with VFR this evening as high clouds thicken, except for a patch of LIFR at the coast from Gold Beach southward. A stable air mass is expected to allow valley LIFR to also form in the Umpqua and Coquille valleys overnight, including Roseburg and North Bend. The low clouds and fog will dissipate after sunrise but a strong front will be approaching. As early as 18Z, late Wednesday morning, showers and isolated thunderstorms may develop from the coast to the Cascades. During the afternoon and early evening, showers and thunderstorms will develop. The risk of thunderstorms will be highest from Douglas County, including Roseburg, northward. But, a slight chance will extend across all of southern Oregon and into Siskiyou County. Besides the showers and thunderstorms, southerly winds will be strong and gusty from late morning through Wednesday evening. Strongest winds are expected in the Shasta Valley and east of the Cascades. Conditions improve later Wednesday night, but another strong front is expected on Thursday. /DW && .MARINE...Updated 230 AM Wednesday, March 26, 2025... Winds will increase into this morning ahead of a strong front. Conditions will rapidly deteriorate with gales developing ahead of a strong cold front. Strong gales will continue later tonight, then conditions rapidly and significantly worsen early Thursday with the next front. Storm force winds are expected, with these south winds and a building heavy long period west swell at 14-15 seconds building very high and dangerous seas of 25 to 30 ft on Thursday. Peak seas are expected Thursday afternoon into the early evening. Winds begin to ease Thursday night, but seas will likely remain very high and very steep into Friday, and high and steep into Saturday. Another strong front is possible Sunday into Monday. This front could move just south of the region which would limit the strength of winds and height of the seas. Stay tuned as details become clearer over the coming days. /DW/Smith && .BEACH HAZARDS...Updated 200 AM Wednesday, March 26, 2025...A long period swell around 25 feet from about 220 degrees will hit the Oregon coast on Thursday resulting in large breaking waves along the beaches. Surf heights will be around 28 to 33 feet throughout most of Thursday. Surf heights will decrease by Thursday evening into Thursday night. These extremely large breaking waves will create very hazardous conditions along beaches and area shorelines. Waves will inundate beaches and surge into normally dry areas. Infrastructure damage and significant beach erosion can be expected. Beaches and coastlines will become dangerous due to very large and life-threatening surf conditions. Stay off of beaches, rocks, jetties, piers, and other waterside infrastructure. /DW && .MFR WATCHES/WARNINGS/ADVISORIES... OR...High Wind Warning from 11 AM this morning to 11 PM PDT Thursday for ORZ021-022-030-031. Wind Advisory from 3 PM this afternoon to 5 AM PDT Friday for ORZ026-029>031. High Surf Warning from 11 AM Thursday to 11 AM PDT Friday for ORZ021-022. CA...High Wind Warning from 11 AM this morning to 11 PM PDT Thursday for CAZ081-085. Wind Advisory from 3 PM this afternoon to 5 AM PDT Friday for CAZ084-085. PACIFIC COASTAL WATERS...Gale Warning from 11 AM this morning to 5 AM PDT Thursday for PZZ350-356-370-376. Gale Warning from 5 PM to 11 PM PDT Thursday for PZZ350-356-370- 376. Storm Warning from 5 AM to 5 PM PDT Thursday for PZZ350-356-370- 376. && $$

221 FXUS66 KEKA 252237 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 337 PM PDT Tue Mar 25 2025 .SYNOPSIS...Warm and dry conditions will last through today beneath a high pressure ridge. A sneaker wave threat will be prevalent through Wednesday as a long period swell dominates the sea state - see the Beach Hazards Statement for more information. Precipitation and strong winds are likely Wednesday through early Friday as a more active pattern sets in. && .DISCUSSION...Warm, summer-like conditions have prevailed for a final day beneath a strong high pressure ridge. Max temperatures will likely near or break records in some interior valleys this afternoon. NBM probability of temperatures exceeding 80 degrees are still high (>75%), although high cloud cover streaming overtop the ridge may slightly dampen these temps. Valleys in southern Mendocino and Lake County are likely to see >85 degrees before the day is out. The coasts also remained mostly clear and warm (>60 degrees), with the stratus deck expected to return late this evening. Cloud cover and southerly winds will begin to increase Wednesday morning ahead of a strong frontal boundary stemming from a deep low pressure system offshore. A wind advisory is in effect beginning at 11AM Wednesday as the initial low level 925 mb jet develops along the north coast. Winds will increase further by mid-afternoon as the frontal boundary moves onshore. Probability of gusts exceeding 45 mph are high (50 to 80%) for northern Humboldt and Del Norte coasts, including Crescent City. Higher gusts are possible through late afternoon. Models continue to highlight potential for convective activity Wednesday afternoon as substantial surface heating generates buoyancy alongside mid level moisture ushered in ahead of the front. SPC includes northern Humboldt, Trinity and Del Norte in thunderstorm threat but Marginal/slight risk is still confined to OR and WA. Still, model reflectivity is beginning to pick up slightly higher dBZ cells within prefrontal showers beginning Wednesday afternoon, especially in eastern Trinity. Winds will remain a rather long term threat as an intensely strong surface low cycles off the OR/WA coast, gradually migrating closer to the coast and tightening the coastal pressure gradient. Winds will likely remain elevated overnight, with gusts 30 to 40 mph likely along the coast and higher elevations of the coast ranges, especially in Del Norte County. Models are in fairly good agreement on the low track, lending favor to another period of particularly strong winds developing Thursday morning/afternoon. 925 mb winds are forecasted to 60 to 70 knots with favorable instability allowing for stronger gusts to mix down to the surface. Gusts exceeding 50-55 mph are possible (NBM: 50 to 65%) in the same wind prone locations through at least 5PM. For precipitation: moderate intensity rainfall is expected to continue beyond the initial front with moist SW flow from the offshore low. Precip will be moderate to locally heavy in Del Norte County and windward ridges of the Kind Range through Friday morning, light to moderate for the rest of the CWA. 3 hour max rainfall rates may approach 0.50 to 0.75 inches in Del Norte/northern Humboldt Thursday afternoon/evening as the low gets closer to the coast. WPC has kept 48 hours totals around 1 to 3 inches for Humboldt, Del Norte, Trinity and northern Mendocino through Friday. Southern Mendo and Lake can expect 0.20 to 0.80 inches with locally higher amounts on higher elevations. The greatest potential for minor flooding concerns will be the secondary surge Thursday afternoon when rain rates will likely be the highest. Snow levels have consistently remained around 3500 to 4000 feet, confining most snow impacts to higher elevations of Highways 3, 36 and 299. 3 to 6 inches are possible by Friday afternoon at Scott Mountain Pass (2 to 4 Thursday afternoon, additional 1 to 3 possible Friday morning. Weak ridging is possible early this weekend before model clusters bring another deep troughing pattern to the PNW on Sunday. Model guidance shows ample QPF and a rapidly deepening surface low approaching the California coast by late Saturday night/Sunday morning. With long range models showing a more active pattern (including CPC highlighting a slight to moderate risk of heavy precipitation 4/1 through 4/3), 10 day river forecasts are starting to note potential for reaching monitor/action stages by next week. Updates to the long term forecast will resolve in the coming days. JMM && .AVIATION...After dense fog this morning, which was amplified by low level inversion and subsidence, the coastal terminals have faired better this afternoon, drastically improving from LIFR to VFR after the fog and stratus layer dissipated. Conditions will maintain through the evening at MVFR or so for the coastal terminals. Of particular concern is the incoming storm system. KCEC could see LLWS by 19z on Wednesday. The probability of gusts > 40 kts climbs upwards from 60% after 22z as winds mix down towards Wednesday evening, rain chances are likely at this time. For a 6 hour accumulation of .05" or greater, we see 70% chance at KCEC by 5pm and 54% chance for KACV. The chance of wetting rain for KUKI is 40% by 5pm tomorrow and consistently looks likely as Wednesday evening approaches. The convective outlook is also of concern with thunderstorms also possible. Fog could be a factor late tonight and in the early morning hours Wednesday. /EYS && .MARINE...Winds are generally light today with gusts below 15 kts through early Wednesday. Winds will gradually turn southerly as an intensifying Pacific cyclone approaches shore. A moderate, lone long period westerly swell around 7 feet will control the sea state today with little wind waves to speak of. Unsettled conditions will quickly build during the day Wednesday. A strong Pacific cyclone is forecast to skirt from south to north across the waters. This will bring strong gale conditions, especially to the northern waters with southerly gusts in excess of 45 kts and reaching storm level gusts (55) near the neighboring Oregon waters offshore, Thursday morning. A Gale Warning has been hoisted for the northern inner and outer waters, Wednesday afternoon Thursday evening. Gusts in the southern waters will be just under Gale thresholds with isolated areas reaching Gale conditions. Small craft advisories are in effect for the southern waters until large southerly waves move in Thursday by 19z, a hazardous seas watch has been hoisted to cover. Regardless, gale winds will steepen short period seas to over 10 feet in all waters by early Thursday, with seas over 17 feet in the northern waters. Gale conditions will most likely begin to ease by late Thursday night, but a very steep mid period westerly swell in excess of 20 feet will build behind the cyclone, maintaining steep and hazardous seas through the end of the week. /JHW /EYS && .BEACH HAZARDS...A long period westerly swell of up to 7 feet will dominate the sea state through the day. With less short period seas to speak of, this swell will create a moderate sneaker wave risk today into early Wednesday. These long period waves can generate sporadic, deceptively calm lulls in wave activity ending with a large set of breaking waves unexpectedly washing far up beaches. Stormy weather will build in Wednesday and Thursday. On the tail end of the storm, a large westerly swell is currently forecast to build in in excess of 23 feet ft which will generate dangerously large surf of 24 to 28 ft on area beaches through the end of the week. A High Surf Advisory is likely to be hoisted for Thursday afternoon which upcoming forecasters will delegate. /JHW /EYS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Beach Hazards Statement through Wednesday afternoon for CAZ101-103-104-109. Wind Advisory from 5 PM Wednesday to 11 PM PDT Thursday for CAZ101. Wind Advisory from 11 AM Wednesday to 11 PM PDT Thursday for CAZ102-104>106. NORTHWEST CALIFORNIA COASTAL WATERS... Gale Warning from noon Wednesday to 9 PM PDT Thursday for PZZ450-470. Small Craft Advisory from noon Wednesday to noon PDT Thursday for PZZ455-475. Hazardous Seas Watch from Thursday afternoon through Thursday evening for PZZ455-475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png

832 FXUS66 KMTR 260851 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 151 AM PDT Wed Mar 26 2025 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 1245 AM PDT Wed Mar 26 2025 There`s a big shift in the weather today as the record breaking heat is over and much cooler temperatures return. Several rounds of rain are in the forecast over the next 7+ days as we enter a more disturbed pattern. && .SHORT TERM... (Today and tonight) Issued at 1245 AM PDT Wed Mar 26 2025 Our glimpse of summer weather was short lived with more seasonal springtime temperatures returning today. The 00Z OAK sounding showed an 850 mb temperature of ~16.4C which narrowly beats the previous 00Z record for March 26th (4PM March 25th) of 15.6C. This resulted in record breaking warmth in the mid 80s to low 90s across the region for the last two days. Why the change up to cooler temperatures starting today? Well, the upper level ridge that has been parked over the West Coast for the last few days is being ejected eastward as an upper level trough and associated surface low move in. The surface low will be located well to our north, closer to Oregon and Washington, but a trailing cold front will extend southward into Northern California. A look at forecast 850 mb temperatures for today shows that they are expected to be around 10C at 00Z March 27th (4PM March 26th). With cooler air being advected into the Bay Area, temperatures will drop 15 to 20 degrees across the region. For those wondering, how noticeable will this drop be? Well, for example, Santa Rosa reached a high of 85 degrees yesterday and is only forecast to reach a high of 64 degrees today. Farther south, Hollister reached a high of 87 degrees yesterday and is forecast to reach a high of 68 degrees today. This pattern holds across the region with most locations expected to be in the 60s. While the PNW is in for a rainy day as this low approaches, residents of the Bay Area may see some precipitation Wednesday ranging from light rain (North Bay) to drizzle (coastal areas south of the Golden Gate Bridge). More rain from this system will arrive Thursday with widespread light rain across the Bay Area. All in all, the North Bay will see up to another 1" of rain from this storm and areas south of the Golden Gate will see up to a quarter of an inch. Winds will be locally gusty between 20 to 25 mph across the higher elevations. The drop in temperatures and the return of rain are a reminder that although summer is close, we aren`t quite there yet. && .LONG TERM... (Thursday through Tuesday) Issued at 1245 AM PDT Wed Mar 26 2025 By Thursday a decaying cutoff low pressure system near the Pacific Northwest will be located poleward of the jet stream. This system will essentially stall while continuing to fill through Friday, but will still have enough strength to continue pumping moisture to the Bay Area. The North Bay will see the highest rain totals, with up to 1/2" possible Friday. The rest of the Bay Area will see anywhere from a few hundreths to 1/4 inch or so. Overall, this will be a mostly beneficial event. Some light rain will likely linger Friday morning and the skies will begin to clear breifly late Friday or early Saturday. After a short break, the next system moves in as a triple point low develops somewhere near the Bay Area Sunday. Overall the rain amounts will be around 1/4" or so for most of the Bay Area and Central Coast, outside of the usual rain shadows (San Jose, San Benito, etc.). The most interesting part of the forecast continues to be around this time next week. By Tuesday, there is a chance that the jet stream will be taking direct aim at the Bay Area. However, the uncertainty remains very high. A look at the cluster analysis reveals that we have roughly equal chances of ridging as troughing, and even then the orientation of the potential trough isn`t clear. The trend has definatley been flatter with the 500 mb flow, which makes a true atmospheric river less likely. The CW3E IVT forecast page shows a 60-70% chance of exceeding 250 IVT along the coast on April 2, but less than a 25% chance of reaching 500 IVT. In summary, we are still expecting heavier rain next week, but the impacts look more manageable lately. On the other hand, it looks like there will be another round or two later in the week. The first week of April looks wet. A multi-ensemble analysis shows that in total by next Friday, SFO can recieve anywhere from 0.5" to 2.5" of rain, with the mean around 1.25". We can handle that. && .AVIATION... (06Z TAFS) Issued at 1028 PM PDT Tue Mar 25 2025 A southerly surge of stratus and mist containing IFR ceilings and visibility is continuing to push up to coast and into the adjacent valleys. Winds will continue to diminish overnight before a moderate to strong SW breeze moves in late morning before some light rain in the afternoon at the northern terminals. Vicinity of SFO...MVFR-IFR CIGs are possible tonight, but most of the impacts will stay on the other side of the coastal mountains. As the disturbance approaches, the marine layer will deepen, allowing MVFR-IFR conditions later in the morning. This system will also bring gusty SW winds and a chance for rain Wednesday evening. SFO Bridge Approach...Similar to SFO Monterey Bay Terminals...IFR-LIFR conditions are firmly in place, with no sign of relief overnight. By late morning, the ceilings should start to break apart, and these terminals will not be as affected by the weather up north through Wednesday afternoon. && .MARINE... (Tonight through next Monday) Issued at 1028 PM PDT Tue Mar 25 2025 Foggy and drizzly conditions are expected across the waters overnight. Light winds continue into the night before turning southerly and becoming moderate to fresh into Wednesday. Seas will flux between moderate and rough through Wednesday. Conditions deteriorate Thursday when a west to northwest breezes become fresh and seas become rough. Unsettled conditions continue through the weekend and into the next work week as storm systems move through the region. && .BEACHES... Issued at 1059 AM PDT Tue Mar 25 2025 A Beach Hazards Statement is in effect through Wednesday morning for all Pacific Coast beaches. In addition to the cold water shock risk that is always present, there will be an increased risk for sneaker waves and rip currents. Observe the ocean for 20 minutes before you pick a spot on the beach, stay off of jetties and rocks, keep pets on a leash, wear a life jacket, and never turn your back on the ocean! && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement until 11 AM PDT this morning for CAZ006- 505-509-529-530. PZ...None. && $$ SHORT TERM...Kennedy LONG TERM....Flynn AVIATION...Flynn MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea

967 FXUS66 KOTX 260949 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 249 AM PDT Wed Mar 26 2025 .SYNOPSIS... Many locations will warm into the 70s today with record temperatures. The heat will come to an end with the potential for strong or isolated severe thunderstorms this evening. Then cooler and unsettled weather will occur Thursday through early next week with several rounds of showers, with snow returning to the mountains as well. && .DISCUSSION... Today and Tonight: Southerly flow ahead of a deep low pressure system well off the southern OR/northern CA coast today will bring additional warming as 850mb temperatures increase to 12-17C with the highest values over SE WA into the ID Panhandle. This will yield high temperatures warming into the 70s with a couple exceptions. One being the LC Valley where Lewiston according to the NBM has a 97% chance of breaking its all time temperature record for the month of March which is 80 degrees. The forecast high for Lewiston is 83F. For the Spokane Airport, there is a 55% chance of the monthly record of 74 being surpassed, with a forecast high of 75 degrees. In addition, numerous daily record high temperatures are expected to be broken today. The other exception to the 70s is the northern valleys. Areas of morning fog and stratus have developed, which should hold high temperatures down into the mid and upper 60s for places like Colville, Bonners Ferry, and Sandpoint. Following the record warmth, attention turns to thunderstorms. The latest CAM`s models are showing little in the way of thunderstorm activity this afternoon as surface based instability is capped. Then heading into the evening CAMS models are showing one high confidence area of larger convection, with a possible secondary area that carries lower confidence. A mid level wave rotating northeast into the Cascades this evening will provide a lifting mechanism to generate an organized area of showers and thunderstorms moving into western WA, with areas of convection developing ahead of it into Central WA. 850-500mb most unstable CAPE of 500-1000 J/KG combined with the atmospheric lift will lead to showers and thunderstorms moving up into the Cascades, and much of Central WA between 6 PM and 10 PM, before tracking into the remainder of Eastern Washington and North Idaho through 1 AM PDT. CAMS models show the potential for isolated damaging wind gusts reaching 60 MPH with this activity, with the Columbia Basin most favored for the higher gusts. Regarding the secondary area of possible convection, this is tied to an instability axis over Eastern OR stretching northward into the Palouse and Central Panhandle Mountains late afternoon into the evening prior to the arrival of the main band of convection. The bulk of the CAM`s models show little to come of this due to instability being capped, but a few solutions show isolated storms developing. This carries lower confidence, but something that will be monitored. While damaging wind gusts are the main threat with storms this evening, isolated large hail of 1" in diameter is also possible. The Storm Prediction Center continues to carry a marginal risk for severe thunderstorms. JW Friday through Saturday night: As the surface low off the coast of the Pacific Northwest weakens, a frontal passage and remnant instability will allow the chance for evening and night thunderstorms to continue through Friday evening. Due to the surface low weakening, severe weather parameters diminish from Thursday, with only a couple hundred J/kg of CAPE anticipated. Still, the remaining instability and the frontal passage bring low chances for thunderstorms to far eastern Washington, particularly to the Lewiston area. Mountain snow is anticipated during this time period as well, with highest elevations having a 50 to 70 percent chance of seeing two inches of snow. Probabilities for four inches of snow drop significantly to 10 to 20 percent, so overall snow amounts will remain light. With the frontal passage, wind gusts in the Columbia Basin and Waterville Plateau will reach 35-40 mph Friday morning through afternoon, and then diminish overnight. By Friday, temperatures will have cooled back down to normal, which for this time of year means high temperatures in the mid 50s. Sunday through Wednesday: While a break from precipitation will be seen by the area on Sunday, the unsettled weather pattern will continue through next week as a series of shortwave troughs make their way across the area. Temperatures will continue to hover around normal through the extended period. Precipitation accumulations with these shortwave troughs will be very light, with only a few inches of snow and less than a quarter inch of rain anticipated in the 72 hour forecast period ending Wednesday morning. /AS && .AVIATION... 06Z TAFS: VFR conditions are currently in place as an upper level ridge sits over the region. Tonight northeast boundary layer winds and continued boundary layer moisture over NE WA/N Idaho Panhandle will allow for areas of shallow fog and stratus to redevelop, with KGEG/KSFF/KCOE the most likely of the TAF sites to be impacted by MVFR to IFR visibilities. If it develops, fog and stratus would improve to VFR by 16Z. The ridge will begin to break down Wednesday afternoon with the potential for strong to severe thunderstorms emerging after 00Z Thursday. This will bring the potential for strong and erratic wind gusts and LLWS along with isolated hail up to a quarter inch in diameter. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is low to moderate confidence for a few hours of fog and stratus to redevelop overnight for KGEG/KSFF/KCOE. There is potential (5% chance) for strong to severe thunderstorms after 00Z Thursday at all TAF sites, but confidence for any specific TAF site is low. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance && .PRELIMINARY POINT TEMPS/POPS... Spokane 75 49 58 42 55 37 / 0 60 60 60 80 30 Coeur d`Alene 72 47 58 40 53 36 / 0 60 70 60 90 50 Pullman 75 47 58 42 53 37 / 0 40 60 50 80 50 Lewiston 83 52 66 47 60 43 / 0 20 40 40 70 60 Colville 66 42 57 37 53 35 / 10 80 80 60 90 60 Sandpoint 64 45 56 39 50 38 / 0 80 90 70 100 70 Kellogg 70 49 56 42 49 39 / 0 50 80 70 100 60 Moses Lake 76 48 61 44 60 36 / 0 60 50 50 20 0 Wenatchee 74 47 58 44 56 37 / 0 80 50 60 40 10 Omak 71 46 61 42 58 38 / 10 80 60 70 80 30 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

432 FXUS66 KPDT 261002 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 302 AM PDT Wed Mar 26 2025 .SHORT TERM...Today through Friday...Primary focus for today is on the threat for strong to severe storms across much of the forecast area, particularly at and along the Cascades. This is due to a robust offshore low that will inject a plume of moisture into the PacNW. This, combined with recent anomalous warmth and moisture, will prime the environment across the Interior Northwest for convection. Overall messaging has changed little since the last forecast. SPC still characterizes the greatest threat for severe storms along and west of the Cascades, due to a more favorable moisture profile, as well as topographic lift assisting in convective initiation. That being said, our forecast area (particularly east of the Cascade slopes) should still expect to see at least isolated activity this evening, due to several factors: 1) Anomalous moisture. Dew points early this morning are reading in the widespread 40s and even 50s, with PWATs up to 0.8 inches across the lower Basin. This is above even the 90th percentile, based on Spokane`s sounding climatology. So while more favorable moisture advection lies to our west, the air mass in the Interior Northwest is still very much charged with moisture. 2) Plentiful instability as MUCAPEs waver from 1000-1600 J/kg across the lower Basin and foothills of the Blues, according to the NAM. This is supported by low-level lapse rates inching towards 9C/km in the lower Basin. 3) A good shear profile as 0-6km bulk shear eclipses 50 kts across much of the forecast area, which would be supportive for long-lived and strong supercells capable of damaging winds and large hail. So while low-level moisture may be lacking east of the Cascades, the ingredients are certainly still there for strong thunderstorms. Confidence is on the lower end for widespread activity across the Basin eastward (30-50% PoPs), owing to the lack of consensus across 06z CAMs runs, but given the environment, am finding it pretty unlikely for areas east of the Cascades to end up bone dry from this event. As far as particular threats are concerned, large hail and strong winds are strong possibilities around storm cells, especially at and along the Cascades. SPC does hint at a 2% chance for tornadoes across the far western sector of our forecast area as well. Low-level SRH is not too promising at around 100-120 m2/s2, but bulk shear does indicate that an isolated tornado cannot be ruled out. Models continue to suggest around 22z-00z (3-5 PM) as when storms first appear across central Oregon before spreading northeastward, with the convective threat generally ending by around 10 PM. Afterwards, we`ll be left in a wet pattern heading into the weekend as the low meanders off the Pacific coast, steadily lifting north and leaving us under a prolonged SW flow pattern. Expect persistent PoPs as a result both Thursday and Friday, with temps cooling back down towards seasonal averages with high pressure out of the way. Rivers/streams are expected to peak around Friday, with many gauges along the foothills of the Cascades and eastern mountains indicating bankfull levels before gradually descending through the weekend. Evans/74 .LONG TERM...Saturday through Wednesday...Weather through the long term period will be dominated by a large low pressure area and trough that will be in the Gulf of Alaska this weekend then will move to the Pacific Northwest Monday through Wednesday. This will give us fairly quiet weather Saturday and Sunday then having a chance of rain and mountain snow after that. Despite the active weather pattern, the Extreme Forecast Index shows little in the way of unusual weather. Model clusters are in good agreement on Saturday in having an upper low and trough 1000 to 1500 miles off the Pacific Northwest coast with a generally westerly flow over our area. On Sunday, models have the trough approaching the coast and the flow turns more southwesterly and warmer. Models do have some differences as the the strength of the trough. Monday is similar with a further progression towards the coast. Differences arise Tuesday as 20 percent of model ensemble members have the trough still roughly 500 miles offshore, 31 percent have it at the coast, 23 percent have it overhead and 26 percent have a building ridge off the California coast. Differences continue Wednesday as 33 percent of the model ensemble members have a trough centered over our area, 26 percent having it several hundred miles offshore, 22 percent have the trough at the coast and the remaining 19 percent have a fairly strong ridge just off the west coast. Overall, forecast confidence is good Saturday through Monday then decreases after that. Saturday will see an upslope flow bringing a chance of very light rain and snow showers over the mountains with snow levels around 3500-4000 feet. Snow amounts will be just a dusting and rain amounts just a couple hundredths of an inch at most. Temperatures will be near normal with highs in the mid 50s to lower 60s in the lower elevations and in the mid 40s to lower 50s in the mountains. Precipitation will end Saturday night and remain dry into Sunday afternoon when the upper low and trough nears the Washington coast and sends a front into central Oregon initially then across the area Sunday night. Brief ridging ahead of the front will warm temperatures a few degrees to the upper 50s to mid 60s with upper 40s to mid 50s in the mountains. Precipitation will be mainly in the mountains and light away from the Cascade crest. Even at the Cascade crest, snow amounts are only about an inch. Snow levels are at 5000 feet, so snow should not affect mountain passes. Monday looks wet as the front crosses the region. The entire area has a chance of precipitation. Snow levels are at 4500 feet and drop to 3500 feet Monday night. QPF amounts are higher with a quarter to half inch in the mountains which translates to up to 3 inches of snow with locally higher amounts. The lower elevations may get up to a tenth of an inch of rain. Temperatures drop back to the mid 50s to lower 60s with 40s and lower 50s in the mountains. Given the model differences that favor a continued trough more than anything else, the NBM keeps a chance of rain and mountain snow over the area Tuesday and Wednesday. QPF amounts Tuesday are again a third to a half inch in the mountains or 1 to 4 inches of snow above 4000 feet while the lower elevations get up to a tenth of an inch of rain. Amounts on Wednesday look significantly lighter. Temperatures Tuesday and Wednesday are a degree or two cooler than Monday. Perry/83 .HYDROLOGY...In response to the current well above normal temperatures, increasing mountain snowmelt is leading to rises on mountain rivers and streams. Rain over the next few days will contribute to these rises. At this time, only the John Day River at Service Creek is forecast to reach minor flood stage Thursday morning through Friday night, peaking at 11.87 feet early Friday morning. The John Day River at Service Creek is expected to reach action stage later this morning and remain there through Sunday evening. The Grande Ronde River at Troy, the Naches River at Cliffdell and Naches and the Yakima River at Umtanum and Kiona are forecast to reach action stage today or tomorrow but none are expected to approach minor flood stage. Most reach action stage briefly but Grande Ronde at Troy and the Naches at Cliffdell are expected to remain at action stage into the weekend. The National Water Model is showing rises on the smaller streams and creeks that do not have formal forecasts, but the rises do not appear high enough to cause problems as they reach levels that occur every year or two. Perry/83 && .AVIATION...06Z TAFs (Previous Discussion)...VFR conditions are very likely (90% chance or greater) for all TAF sites overnight through Wednesday morning. Winds through mid-morning Wednesday are forecast to be terrain- driven at 10 kts or less. Wednesday afternoon, the focus shifts to a convective threat with medium confidence (40-60%) in isolated to scattered showers and thunderstorms spreading from south to north across central Oregon into south-central Washington from roughly 22Z Wednesday through 06Z Thursday. All TAF sites have a high enough chance of thunder to include a PROB30 in the 06Z TAFs. Additionally, our forecast area of responsibility, including all TAF sites, is under a Marginal Risk (level 1 of 5) for severe thunderstorms. Any showers and thunderstorms that develop will be capable of producing strong, gusty outflow winds up to 60 mph and hail up to 1 inch in diameter. Plunkett/86 && .PRELIMINARY POINT TEMPS/POPS... PDT 81 49 66 47 / 10 30 40 30 ALW 80 51 64 48 / 10 40 50 40 PSC 78 49 65 47 / 0 40 50 30 YKM 76 46 60 43 / 0 80 30 40 HRI 79 48 66 47 / 10 40 50 30 ELN 73 45 58 41 / 0 90 30 40 RDM 80 42 61 39 / 20 40 20 20 LGD 74 46 63 43 / 10 10 40 20 GCD 77 47 61 41 / 20 20 40 20 DLS 77 48 60 45 / 20 90 60 60 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...74 LONG TERM....83 HYDROLOGY...83 AVIATION...86

230 FXUS65 KREV 260924 AFDREV Area Forecast Discussion National Weather Service Reno NV 224 AM PDT Wed Mar 26 2025 .KEY MESSAGES... * Winds increase today from the southwest, and continue to increase into Thursday when winds become strong and gusty. * Sierra showers begin this afternoon, with a wet and cool pattern remaining for the rest of the week. * A series of systems will provide a wet and cool start to the month of April. && .DISCUSSION... Today will not be quite as warm across the western Nevada valleys, although some valleys along US-95 look to achieve another 80 degree day before a system moves in to change up our warming trend. Early this morning will be a relatively quiet start, but winds will begin to pick up along the Sierra ridges by late morning. This will signal the arrival of the next system to bring showers to the Sierra. Snow levels this morning are well above 9000 feet, so this first round of early afternoon showers will largely be rain. In fact, snow levels will remain elevated above pass level until the frontal passage allows for a tap into cooler air for Thursday. This later onset of snow showers will limit snow accumulations, with a 40- 50% chance for Donner Pass to receive 3 inches of snow by Friday morning. As the system rotates inland, waves of precipitation will continue through Saturday, bringing an additional 5 to 8 inches to pass level. As for the southwesterly winds at the front of this system, today`s afternoon gusts will approach 75-80 mph on the ridges, 55 to 60 mph for wind prone areas and western Nevada valleys. If those winds speeds don`t impress, Thursday will be another strong wind day, with a High Wind Watch for midday Thursday through Thursday night. Gusts on the ridges will approach 100+ mph, wind prone and leeside valley areas will see gusts to 75-80 mph. A Lake Wind Advisory for both Lake Tahoe and Pyramid Lake has been issued for today. Hang onto your hats, secure lawn furniture and decor and prepare for choppy lakes, bumpy air travel, and blustery roadways including blowing dust near desert sinks and dry lake beds. Saturday evening will offer a brief break, but yet another wave of moisture approaches for Sunday. This is part of the series of waves that will keep showers in the forecast through the end of March into early April. The moisture source of this atmospheric river is shown by the GEFS to contain an integrated water vapor of 250 kg/(ms) for the foothills of the western Sierra. While the confidence around the moisture profile is moderate, the temperature profile with this system is less clear. Ample moisture suggests a warmer airmass, although the backside of this frontal system may be cold enough to support snow down to around 6000 feet. Should this system come in as a wetter, warmer system there could be some concerns for rising rivers as snow melt and rains could combine to create issues. Stay tunes as we work through the details for the early April system. HRICH && .AVIATION... * FL100 winds increase from the SW to 40-50 kts by 21Z Wednesday and continue through 06Z Friday. Therefore, there is an increased chance for MDT-SVR mountain wave turbulence along with LLWS at Sierra (KSVE-KTRK-KTVL), and far western NV (KRTS-KRNO- KCXP-KMEV) terminals. Surface wind gusts Wednesday at main terminals will increase to 20-30kts, and increase further on Thursday with the potential of peaking at 40-50kts in the afternoon. * Saturday for valley terminals will see the return to VFR conditions, with Sierra terminals wrapping up the showers as they exit by Saturday evening. Sunday another system approaches the Sierra, bringing gusty ridges and showers back to Sierra terminals for the afternoon, and potentially down to leeside valley terminals by Sunday evening.-Amanda/HRICH && .REV Watches/Warnings/Advisories... NV...High Wind Watch from Thursday morning through Thursday evening NVZ001-003>005. Lake Wind Advisory from 2 PM this afternoon to 8 PM PDT Thursday NVZ002. Lake Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening NVZ004. CA...High Wind Watch from Thursday morning through Thursday evening CAZ070-071. Lake Wind Advisory from 2 PM this afternoon to 8 PM PDT Thursday CAZ072. && $$

649 FXUS66 KSTO 260914 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 214 AM PDT Wed Mar 26 2025 .Discussion... .Key Messages... * Wind Advisory: 2 pm this afternoon - 8 pm Thursday evening. Wind gusts up to 45 mph north/central Sacramento Valley and adjacent foothills. * Slight chance (20%) of Isolated Afternoon/Evening Thunderstorms Today-Friday...main risk Shasta County and adjacent foothills. * Periods of light to moderate mountain snow Thursday through Saturday morning. Snow levels 4000-5000 feet. 48-hour Probability of snowfall > 4 inches: 40 to 70 percent above 5000 feet along Sierra/southern Cascades. * Brief lull Saturday followed by a return to active weather Sunday into next week. Periods of at least light to moderate rain/mountain snow expected with gusty winds and isolated thunderstorms possible. * Sunday-Monday System: Snow levels 4500-5500 feet. 48-hour Probability of snowfall > 4 inches: 30 to 60 percent above 5500 feet along Sierra/southern Cascades. * Tuesday-Wednesday System: Snow levels 5000-6000 feet. 48-hour Probability of snowfall > 8 inches: 20 to 50 percent above 5500 feet along Sierra/southern Cascades. .Changes from previous forecast... * Slight uptick in expected wind gusts today and Thursday. * Isolated thunderstorm chances persist through the end of the week. * Snowfall totals through Saturday morning trending upward. && .AVIATION... VFR conditions prevail over the next 24 hours across interior NorCal. Surface winds below 12 knots until around 18z today, when winds will shift to from the south with gusts up to 40 knots, especially in the northern Sacramento Valley and adjacent foothills. Isolated light rain showers in the northern Sacramento Valley beginning around 00z Thursday. Elsewhere in the Valley, southerly surface gusts up to around 25 knots next 24 hours. In the mountains, gusts up to 50 knots. && .STO WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 2 PM this afternoon to 8 PM PDT Thursday for Central Sacramento Valley-Northeast Foothills/Sacramento Valley- Northern Sacramento Valley. && $$

327 FXUS65 KMSO 260914 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 314 AM MDT Wed Mar 26 2025 .DISCUSSION... KEY MESSAGES: - High confidence in above-normal temperatures today. - Strong thunderstorms possible for portions of Idaho/Clearwater counties this evening. Main threat wind gusts up to 40 mph, with a 5% probability of severe winds and hail. - Active pattern returns this tomorrow through early April. High pressure will remain over the Northern Rockies today, allowing for another nice Spring day, with temperatures 10 to 20 degrees above normal. Most locations will also see overnight temperatures remain above freezing, which will help accelerate snowmelt in the mid and upper elevations. Local streams and creeks will see rises, though flooding is not anticipated at this time. Thunderstorms are still expected to develop this evening into early Thursday morning ahead of an approaching cold front. The main focus will be across north central Idaho, including Idaho and Clearwater Counties. Enough instability will be available to allow for a few storms to become strong. The main threat will be wind gusts up to 40 mph, though hail cannot be ruled out. The storm prediction center continues to show a roughly 5 percent chance that a storm could become severe, capable of gusts nearing 60 mph. The cold front will pass through western Montana and north central Idaho during the day Thursday. The frontal progression is slower than previous model runs, which will maintain mild temperatures through much of the day, especially in western Montana. The front will bring breezy southwest to west winds, with widespread gusts to 25 mph. Winds could be further enhanced by showers/thunderstorms. This may create choppy conditions for those recreating on area lakes. A lake wind advisory remains a possibility for Flathead Lake Thursday afternoon. Friday into the weekend will see more seasonal, active weather return as a trough of low pressure moves into the Pacific northwest. This setup favors below-average temperatures and above-average precipitation continuing into early April. Periods of snow on mountain passes can be expected, especially in overnight and early morning hours. && .AVIATION...Another nice day is expected for most of the day across the Northern Rockies. Instability ahead of an approaching trough, will allow for scattered showers and thunderstorms this evening for Idaho and Clearwater counties. The main threat from these thunderstorms will be gusty winds around 30kts. A cold front associated with the trough is expected to arrive to north-central Idaho and western Montana Thursday afternoon and evening, that will bring widespread west to southwest winds of 25kts, along with scattered showers and thunderstorms. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

476 FXUS65 KBOI 260850 AFDBOI Area Forecast Discussion National Weather Service Boise ID 250 AM MDT Wed Mar 26 2025 .SHORT TERM...Today through Friday night...A strong high- amplitude ridge will dominate the region through the first part of today, bringing near-record to record-breaking warmth across the forecast area. Portions of the Treasure Valley could reach the low 80s, making this one of the warmest days of the season so far. Later today, this warm and unstable airmass will precede an approaching Pacific low-pressure system and its associated cold front, expected to arrive tonight. Atmospheric instability is notable, with CAPE values near 700 J/KG and shear around 45 knots across southeast Oregon and the higher terrain of southwest Idahoboth in the 95th percentile. These conditions, combined with diffluent flow aloft and strong southerly deep- layer winds, present a favorable setup for isolated severe thunderstorms. However, limited moisture, especially across southwest Idaho, will likely constrain storm development. This is further supported by the Satellite imagery showing only sparse cumulus formation over the Great Basin yesterday. High-resolution models have reduced overall convection for this afternoon and evening, with storm activity now primarily expected over the higher terrain of northern Harney, northern Malheur, and Baker counties. Some high-resolution models also suggest brief thunderstorm development near the Owyhee Mountains late this afternoon (between 3 PM and 6 PM), but these storms are likely to be short-lived due to less favorable conditions over the Snake River Plain. Forecast soundings show Inverted-V profilestypically seen in summersuggesting that the strongest storms are likely (5% chance) to produce strong outflow winds and hail. By Thursday, the low-pressure system will reach the Pacific Northwest coast, pushing a cold front through the region and lowering temperatures by 10-15 degrees from Wednesdays highs. Gusty winds will accompany the front, with peak gusts of 50 mph possible near the Nevada border in southeast Oregon. Showers will also develop, with a 50-80% chance of precipitation in the mountains and a 20-50% chance in the valleys. An embedded shortwave within the southwest flow will increase the potential for thunderstorm development (15% chance) Thursday afternoon and evening. Snow levels will gradually drop from around 9,000 feet MSL today to between 6,000 and 8,000 feet MSL by Thursday. Any snowfall accumulations will be confined to the highest peaks. By Friday, additional moisture will spread across the region as the system lingers near the Pacific Northwest coast, bringing scattered showers. There will also be enough instability to support a slight chance (less than 20%) of afternoon and evening thunderstorms. Temperatures will cool to near-normal levels, and it will remain breezy. Snow levels will be low enough for light accumulations in mountain areas above 5,500 feet. .LONG TERM...Saturday through Wednesday...Unsettled weather continues through mid-week next week. The first of multiple impulses is set to pass through the area Saturday. This is resulting in a 20-30% chance of precipitation in lower elevations and 60-80% in the West-Central ID and Owyhee mtns, snow levels 4000-5000ft MSL increasing from west to east. Sunday is looking to be the one dry day, as shortwave ridging builds in behind the vacating trough. Precipitation chances return early Monday morning as the next system begins to move through. Both GFS and ECMWF ensembles are hinting at instability building into the area Monday afternoon. However, have opted to keep the mention of thunder out of the forecast for now and will continue to monitor the potential. Snow levels ranging from 5000-6000 ft MSL Monday. Precipitation chances remain elevated through Wednesday, with a 30-50% chance in lower elevations and 60- 80% chance in higher elevations. Snow levels lowering to 4000-6000ft MSL Tuesday following a cold frontal passage. Temperatures throughout the long term hover near normal. Leaning slightly below normal Tuesday and Wednesday. && .AVIATION...VFR. Decreasing confidence in fog formation near KMYL this morning. Isolated storms and showers this afternoon and evening. A slower than expected front means formation is too low for TAF inclusion at most sites. However, there will be enough instability and moisture for sparse development over terrain, so collapsing storms and outflows of up to 40 kt could reach valley sites. Surface winds: SE 5-15 kt in the Snake Plain, light and variable elswhere, becoming SW 15-30 kt in SE OR this afternoon. Winds aloft at 10kft: S 5-20 kt. KBOI...VFR. Storm/shower development in the vicinity is unlikely, but collapsing storms moving off the Owyhees could still impact the site. Surface winds: SE 5-15 kt, with gusts to 25 kt this afternoon. Outflow gusts up to 40 kt are possible out of storms. && .HYDROLOGY...Snowmelt will cause rising water levels in rivers, creeks, and streams across southeast Oregon and southwest Idaho over the next several days. Those with interests near waterways should stay alert to changing conditions. A Flood Warning remains in effect for the Silvies River near Burns, Oregon. An active weather pattern, as indicated by the CPC 8-14 day outlook, may contribute to additional river rises into early April. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise SHORT TERM...JDS LONG TERM....NF AVIATION.....JM HYDROLOGY....JDS

453 FXUS65 KLKN 260948 AFDLKN Area Forecast Discussion National Weather Service Elko NV 248 AM PDT Wed Mar 26 2025 .SYNOPSIS...Near-record to record warmth this afternoon. Southwesterly winds on Thursday become gusty, with areas of blowing dust likely. A cold front passes through the region later on Thursday with the return of unsettled weather and cooler temperatures through the remainder of the weekend. && .SHORT TERM...Today through Thursday night. An upper level low currently over the eastern Pacific Ocean will move in along the northern CA and Oregon coastlines by this afternoon, which will replace the ridge over NV with an even warmer southwesterly flow aloft. SW winds increase by this afternoon across most of northern and central NV, however all winds are expected to remain below advisory levels. That said, strongest winds of 15 to 25 mph with gusts to 40 mph are expected over NW Nevada this afternoon, including most of Humboldt and portions of Lander county. These areas may experience patchy blowing dust in the afternoon and early evening hours. The increasing southwesterly flow over NV will also bring weak instability to much of northern NV. Held off on adding any thunderstorm wording to the forecast this afternoon as mid-level moisture is very limited, though much of the region could see afternoon and early evening cumulus build-ups, with a 5-10% chance of lightning. Best chance for a couple strikes would be over far northeastern Elko County late this afternoon. Otherwise, the warming trend continues today with near-record to record high temperatures. Tonight into Thursday the upper level low off the west coast pushes onshore into CA/OR/WA and NV. Stronger winds on Thursday with Advisory to possibly Warning level winds over mainly Humboldt County from late Thursday morning through the mid-evening hours. For now issued a High Wind Watch for Humboldt County Thursday. At this time it looks as though winds across Humboldt County on Thursday will be Advisory levels in valleys with Warning levels over the highest terrain. As for the rest of the CWA on Thursday, winds will be gusty across the region, though for now winds look to be below Advisory levels in most all valley areas. Blowing dust will be more of a concern Thursday afternoon and early evening across mainly the westerly half of the CWA (including all of Humboldt, western Elko, and much of Lander and Eureka counties) where periods of reduced visibilities are likely. Dust may reach Carlin and Elko by late Thursday afternoon or early evening. Highs on Thursday will be 5-8 degrees cooler than this afternoon for most locations, though still well above normal for this time of year. Additionally, the warm and unstable airmass will increase the chances of isolated thunderstorm activity Thursday afternoon and early evening, with the best chances (10-20%) across the eastern half of Elko County. .LONG TERM...Friday through next Tuesday A low pressure system will approach the Pacific Northwest coast on Thursday, influencing our weather later this week and early next week. Long-range ensemble cluster models show a persistent, longwave trough off the Pacific Northwest coast, with several shortwaves moving east through Nevada on the edge of the low. This will bring a pattern change from warm, dry weather and near- record highs, to normal temperature and precipitation amounts for this time of year. The first shortwave will exit our area on Friday, leaving behind light snow accumulations. A trace of snow in lower elevations and 1-2 inches in the mountain ranges above 6,500 feet are forecast. No impacts are expected on any roadways. A second shortwave trough on Saturday will bring more widespread snow, with a trace to 0.5 inches in the valleys. Confidence in amounts is low in areas below 6,500 feet in elevation. The trough will clear out by the evening, with a brief break in the weather on Sunday. On Monday, another low pressure system will approach the Pacific Northwest coast, bringing precipitation and gusty winds to our area on Monday and Tuesday. && .AVIATION...VFR conditions are expected at all terminals through Wednesday afternoon under high pressure. No precipitation is anticipated at this time. Winds at all terminals will remain below 11KTs through midday on Wednesday. KTPH and KELY terminals will see wind gusts in the 18-20KT range Wednesday afternoon. && .HYDROLOGY...High pressure persisting across the Great Basin will bring record to near record warm temperatures. This will help to increase the melt rate of mid and high-elevation snowpack, which will make it into area creeks and streams. Faster responding creeks that will need to be watched for higher flows include Martin Creek in Humboldt County, the Owyhee River, Bruneau River, and Salmon Falls Creek in Elko County. The Bruneau River experienced a moderate rise Tuesday afternoon and evening, and at this time is the river with the best chance to reach action stage (6.0 feet) later this Wednesday evening and overnight. The Bruneau River is not expected to reach minor flood stage (7.0 feet) however. Though flooding is not expected on any regional creeks or rivers at this time, water will be flowing strongly. Residents and outdoor enthusiasts are urged to use caution when walking along riverbanks as run off water will be flowing rapidly with cold spring melt water. Hypothermia can occur rapidly if someone were to fall in while swift flows can carry a person downstream. && .CLIMATE... Max Temp Record | % Chance of tying | Year of record Date KEKO KELY KP68 KTPH KWMC 3-26 73|100|1988 73|96|2022 76|80|2022 77|77|2022 77|97|2022 3-27 76| 1|2022 74|98|2015 77| 4|2015 78| 3|2015 78| 0|2015 && .LKN Watches/Warnings/Advisories... High Wind Watch from Thursday morning through Thursday evening Humboldt. && $$ 96/99/89