826 FXUS66 KSEW 182213 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 313 PM PDT Tue Aug 18 2026 .SYNOPSIS...Weak upper level ridge over the area through Thursday with varying degrees of low level onshore flow. Upper level low well offshore slowly moving northeast and off the coast Friday. Weak system spinning out of the low could produce some showers over the area Friday. Low moving through Saturday keeping a chance of showers in the forecast for some locations. Weak upper level ridge with low level onshore flow returns later Sunday into the first part of next week. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...Weak upper level ridging will lead to dry and mild weather across western WA through Thursday. The low level flow remains onshore. Temperatures will track close to average with a slight uptick on Thursday. 33 && .LONG TERM /FRIDAY THROUGH TUESDAY/...An upper level low will spin offshore on Friday, then shift inland on Saturday for increasing showers and cooler weather. The air mass will be slightly unstable for a chance of thunderstorms in the mountains Saturday afternoon (eastern Olympics and northern Cascades). Highest chances for wetting rains will be in the northern Cascades near the Canadian border. With the trough overhead, expect cooler conditions on Saturday with highs in the 60s to lower 70s. We`ll see lingering showers on Sunday as the trough exits NE. Otherwise, were back to dry and mild weather moving into next week as weak high pressure returns. 33 && .AVIATION...VFR this afternoon for interior terminals and MVFR along the coast. Conditions will deteriorate tonight into Wednesday morning as another round of marine stratus pushes inland. Guidance continues to struggle with how low the ceilings will get, but based of persistence, it is possible that that ceilings will trend toward IFR/LIFR again. High-res guidance shows there is a 50-70% chance for IFR/LIFR for the interior terminals. Additionally, reductions in visibility are possible with the stratus. Uncertainty remains as to how low visibility will be, but could see visibilities lower than 3SM. The stratus will retreat towards the coast/scatter out in the afternoon after 19Z. VFR for interior terminals in the afternoon/evening and minimal improvement along the coast to MVFR. Generally SW winds this afternoon. Winds may transition WNW at BFI/SEA this evening between 00-06Z. Probabilities are slightly higher for BFI to see WNW, with probabilities trending towards 70- 80%. Otherwise, calm to light SW winds overnight. KSEA...VFR will prevail today. While guidance continues to struggle with how low the ceilings will be Wednesday morning, some high-res guidance has a 50% chance for LIFR and 65% for IFR after 12Z. Based off persistence, will trend the TAF towards IFR/LIFR for tomorrow morning. Ceilings will slowly improve throughout the late morning and scatter out by the afternoon, with VFR for Wednesday afternoon. Generally SW winds 3-6 kt today. Winds will shift more towards the WSW this evening and may switch WNW (60% chance) between 01-06Z, but should remain light around 5 kt. Light WSW winds overnight. 29 && .MARINE...Broad high pressure over the northeast Pacific will continue building into area waters through tomorrow. A weak system will approach the waters today, but is not expected to significant impacts. Increased NW surface winds through Wednesday and are expected to remain below SCA thresholds. High pressure will then weaken through late in the week as a stronger weather system approaches and moves over the waters on Friday. This may result in SCA winds through the Strait of Juan de Fuca Friday evening, with latest probabilities around 60-70% through the central portion. Over the weekend, high pressure will rebuild and strengthen over area waters. Seas will remain below 10 feet throughout the week. However, seas may become steep at times for the outer coastal waters today through Thursday at 5-7 ft with a dominant period of 7 seconds. 29 && .FIRE WEATHER...Continued onshore flow through Thursday will maintain mild temperatures paired with excellent overnight relative humidity recoveries, limiting fire weather concerns across western Washington. A storm system approaching the region will cause elevated fire weather concerns on Friday, bringing increased potential for thunderstorms over the Olympics and Cascades. While there is still a bit of uncertainty with the timing and intensity of this weather system, any thunderstorms that develop may be capable of producing locally wetting rains alongside gusty and erratic outflow winds and abundant lightning. While convection may continue overnight, a frontal system will cross the region sometime between Friday evening and Saturday, bringing in a much cooler and more moist air mass. Widespread gusty winds are not expected behind the frontal passage, though models continue to show potential for convection and a potential Puget Sound Convergence Zone on Saturday. Fire weather concerns decrease into Sunday, as a drier and calmer pattern sets up over western Washington. This will likely bring a return to onshore flow with morning low stratus and afternoon sun, near normal temperatures, and generally calm winds. 15 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

876 FXUS66 KPQR 182030 AFDPQR Area Forecast Discussion National Weather Service Portland OR 130 PM PDT Tue Aug 18 2026 .SYNOPSIS...Warm and dry conditions expected through much of the week with morning clouds and afternoon clearing. Daytime highs are expected to be in the 80s through the week. Winds generally out of the west to northwest through Thursday, strongest in the afternoon and along the Central Columbia River Gorge and Upper Hood River Valley. Low chances for light showers arrive Thursday night through Saturday, but conditions most likely remain dry, along with 5-10% chance for evening thunderstorms along the Cascades. Seasonable weather continues late this weekend into early next week. && .DISCUSSION...Tonight through Monday...The overall forecast remains stagnant with little change to the forecast as predominately dry and warm conditions continue through the week with minimal impacts. The synoptic pattern through the mid-week remains stagnant as a col will continue to dominate the Pac NW. This col continues to be defined by a high over the Great Basin and a low within the eastern Pacific. While there is a mirrored high over the Gulf of Alaska and mirrored low over the central provinces of Canada, these two systems are not as impactful as the ones closer to CONUS. Overall, this pattern will support continued onshore flow at the surface, which will maintain near- normal daily high temperatures in the 80s within inland valleys and 60s along the coast, and overnight lows in the 50s across the region. With moist air flowing into the region, each night will be characterized by marine stratus along the coast with some stratus filtering into the I-5 corridor. These clouds should clear out each afternoon as daytime heating progresses. Expect light winds from the west/northwest for most places, peaking each afternoon. An exception would be the Central Columbia River Gorge and Hood River Valley, where west winds will be strongest with gusts approaching 30-35 mph through the evening. The majority of ensemble members are in agreement that aforementioned upper-level ridging over the Rockies and Great Basin will start to dominate on Thursday and will result in a brief warm up across the CWA. However, that warm-up will likely be short-lived as ensemble guidance continues to show the eastern Pacific low moves northeast-ward Thursday through Saturday. This will bring a return of slightly cooler temperatures as well as a southerly wind shift. This southeasterly flow is a favorable pattern for precipitation as well as thunderstorms. However, the overall atmosphere continues to remain dry, thereby limiting the potential for any precipitation. But, models are starting to show some general, elevated instability from Thursday through Saturday. So, this will bear continue scrutiny through the remainder of the week. It should be noted, that there remains a lot of uncertainty as to the exact timing of the Pacific low, as some ensembles have the low moving into the region as early as Thursday evening, while others push it out around 24 hours (Friday evening). To summarize the summary, there is a 5-10% chance for elevated thunderstorms for the Cascades from Thursday through Saturday, starting in the late afternoon through the overnight hours each day. Late this weekend into early next week, the trough weakens and most ensemble members suggest a return of zonal flow before another upper-level trough drops down from the Gulf of Alaska and approaches British Columbia. At this point, there still remains a fair amount of uncertainty with the exact magnitude and placement of the late weekend/early next week trough. However, this would suggest that onshore flow continues across the region resulting in seasonable temperatures for late August. /42-10 && .AVIATION...Through 00z Thursday...Marine stratus remains socked in at the coast with predominately MVFR/IFR conditions are expected along the coast over the next 24 hours, though there`s a 20-30% chance terminals could briefly become VFR at any hour through 02z Wed. There`s also a 60-90% chance of LIFR conditions returning at any hour 00-18z Wed. Expecting MVFR/IFR conditions to form in the SW WA lowlands and Portland metro area south to KAST between 12-15z Wed, improving to VFR by 17-19z Wed. Westerly to northwesterly winds across all terminals peaking this afternoon and evening up to 8-10 kts before decreasing to 2-6 kts overnight. KPDX AND APPROACHES...VFR conditions with mostly clear skies through Tuesday evening. MVFR/IFR stratus expected to return after 12z Wed, improving to VFR once again by 17-19z Wed. Northwesterly winds 4-7 kt. -03 && .MARINE...A largely stagnant pattern continues through much of the week with high pressure offshore supporting northerly to northwesterly winds of 8-15 kt and afternoon and evening gusts up to 15-20 kt. Weak low pressure moving over the northeast Pacific Friday into the weekend will shift winds out of the south to southwest across the waters, but chances for gusts exceeding 21 kt remain low, only 5% or less. High pressure and northerly winds return by Sunday with a 30-50% chance of northerly wind gusts exceeding 21 kts in the afternoon and evening hours south of Cape Falcon. Seas of 3-6 ft persist through the period. Increasing periods of 12-14 sec today and Wednesday may result in a moderate risk for sneaker waves along the coast. Caution should be used when in or near the water. -03/10 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

738 FXUS66 KMFR 182122 AFDMFR Area Forecast Discussion National Weather Service Medford OR 222 PM PDT Tue Aug 18 2026 .KEY MESSAGES... * Dry weather is expected for inland areas through Thursday with above normal warmth and fairly typical afternoon breezes. * Nightly marine pushes will bring cooler air and stratus to the coast, and also a chance of drizzle. * Offshore low pressure brings heightened fire weather concerns Friday with gusty winds and at least a slight chance of thunderstorms. * Breezy winds continue Saturday with a slight cool down. * Dry, warmer weather returns Sunday/Monday. && .DISCUSSION...Upper ridging will amplify a bit over the area through Thursday resulting in above average warmth for inland areas (NWS HeatRisk tops out as minor with pockets of moderate, especially in the typically hotter valleys). Despite the elevated risk, this type of heat is common for late August and primarily impacts those who have heat sensitivities or lack adequate cooling/hydration systems). Even so, this will be a hotter period, so try to find ways to keep cool and stay hydrated. Expect highs in the mid to upper 90s for the west side valleys south of the Umpqua Divide with even some triple digit readings in the lower Klamath river valley of western Siskiyou County. East side locations and the Umpqua Basin will have highs in the upper 80s and lower 90s. Nightly marine pushes will continue at the coast bringing periods of low stratus/fog and even a chance of drizzle at times. From around Port Orford to Gold Beach, it should stay comparatively clear due to a slight offshore wind component. Coastal areas will have highs in the 60s/low 70s. A closed low well offshore will get a kick north-northeastward Friday into Saturday as it gets absorbed into the westerlies. At the very least, this will bring an increase in W-SW winds in NorCal and from the Cascades eastward and NW winds in the west side valleys Friday. Models continue to differ on timing, strength and position of the low as it moves northeastward across the PacNW. And, this has some impact on the forecast - especially thunderstorm chances. Will the low be close enough to the coast so that forcing is better or far enough offshore that most of the forcing stays offshore or to our north? There should at least be some moisture and instability available due to SSW flow aloft. So, there`s a slight chance of showers and thunderstorms Friday afternoon/evening, but the best chances at this time are up across the north (easternmost Douglas, northernmost Klamath/Lake counties). The associated upper trough should swing through on Saturday. By then, most of the moisture will lift to the north (mentionable PoPs stay north), but gusty afternoon/evening W-NW breezes could persist. Either way, we should see a cooling trend Fri/Sat compared to the mid week warmth. It should dry out and turn warmer again Sunday/Monday with the flow aloft turning more into the south Monday into mid next week. This could increase chances for t-storms again, but it`s only a low chance at this time (5-10%). -Spilde && .AVIATION...18/18Z TAFs...Satellite imagery shows stubborn marine stratus along the coast north of Cape Blanco, including at North Bend and south of Pistol River, including at Brookings. This is resulting in IFR ceilings currently at North Bend and LIFR ceilings/fog at Brookings. Sandwiched in between is an area of VFR (Gold Beach to Port Orford) due to a more offshore wind component. Where the lower conditions are currently, we expect conditions to improve somewhat this afternoon with some areas scattering out to VFR around 21Z, but this will be short-lived. We expect IFR/LIFR conditions to redevelop this evening and continue overnight into Wednesday morning. Inland, mainly VFR is expected through Wednesday morning with just some high and mid level clouds. -Spilde && .MARINE...Updated 230 PM PDT Tuesday, August 18, 2026...Gusty north winds and steep seas, highest during the afternoons and evenings are expected south of Cape Blanco through Wednesday evening. Conditions are expected to improve Thursday and Friday. A thermal trough will redevelop along the coast this weekend bringing a return of strong north winds and steep seas. Once again, strongest winds and highest seas are most likely south of Cape Blanco. -Spilde && .FIRE WEATHER...Updated 130 PM PDT Tuesday, August 18, 2026...Aside from some enhanced afternoon breezes today, fire weather concerns will remain fairly standard for this time of year through Wednesday. Expect typical summer conditions with dry weather across the area and nightly marine pushes along the coast. Temperatures will trend upward today through Thursday, resulting in a downward trend in afternoon RHs. Overall, recoveries will remain in the moderate to good range, though poor to moderate recoveries are expected along and east of the Warners as well as the Salmon Mountains in western Siskiyou County through Friday morning. Thursday will be a transition day into a pattern that brings some heightened fire weather concerns. A stronger upper level trough, currently spinning out beyond 140 W, will gradually move eastward this week, moving inside of 130 W by Thursday. This will start a period of increased winds that will likely persist through Saturday as this low pressure gradually moves inland into the PacNW through the weekend. Gusty winds are expected to develop Thursday afternoon as the trough nudges closer, and this could overlap with low RHs in portions of northern California and east of the Cascades, possibly resulting in critical conditions on Thursday. There is some uncertainty regarding just how strong winds get and this could be the limiting factor on Thursday. There are subtle differences in the model guidance on how close to shore that low pressure is on Thursday, which will be a player in how strong winds are. Gusts 15 to 25 mph will be common across the region, but if the closer to shore solutions are correct, the windiest locations (Shasta Valley/East Side) could see gusts of 25-30 mph on Thursday. Confidence is higher for winds to peak on Friday (gusts 25-35 mph), but the limiting factor for critical conditions could be the uptick in daytime humidities expected Friday as temperatures trend cooler. In addition to winds/RH concerns for Friday, mid-level moisture increases Thursday and Friday, raising the concern for thunderstorms potential. Current guidance indicates that the best chance for storm development would be along the Cascades from Crater Lake northward and across northern Klamath/Lake Counties. With the approach of the trough Thursday night into Friday, we`re monitoring the potential for any nocturnal convection, but current guidance is steering clear of that for now. Heading into Saturday, models differ a bit on how fast that trough moves through the region, but confidence is fairly good that the thunderstorm threat will shift north of the area. The question that lingers from these differing solutions is how strong will winds be on Saturday, especially east of the Cascades. While it`s likely to be another breezy day, most areas should see weaker winds on Saturday compared to Friday. Some solutions would maintain another day of stronger winds across the Modoc Plateau and east of the Warner Mountains. Regardless, daytime RHs look similar to what`s expected Friday, so again, that could be limiting factor for critical conditions on Saturday. Stay tuned for updates. /BR-y && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Wednesday for PZZ356-376. && $$ MAS/BR-y

559 FXUS66 KEKA 182226 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 326 PM PDT Tue Aug 18 2026 .KEY MESSAGES... * Thick smoke remains stuck around the Hoopa Valley stretching from as far north as to Orleans as far south as the middle Eel River Valley. Weak transport winds will keep smoke here through the week. * Interior temperatures peaking Tuesday will ease through the week with persistent marine influence along shore. * Another trough is expected to bring below normal temperatures and very slight potential for a isolated thunderstorms Friday. && .SYNOPSIS...Warm temperatures will ease through the week tanks to increasing marine influence. Marine clouds will persistent along shore with some slightly better clearing chances late week. && .DISCUSSION...High pressure has peaked across the area today, allowing many interior locations to reach into the upper 90s. Besides a thin and slow to recede marine layer near shore, clear skies and gentle west winds have persisted. Smoke has continued to sock in valleys around the MP18 fire in Hoopa with smoke pushing up the Trinity River with afternoon terrain winds. An elongated trough will gradually approach shore through the end of the week. This will help push marine influence further inland and weaken high pressure, allowing interior highs to pull back into the upper 80s by late in the week. Increasing marine influence will most likely help strengthen and deepen the marine layer along shore, a deeper and slightly more unstable marine layer may allow for better scattering in the late afternoons. The trough will certainly bring a string of high clouds across the area around Friday, helping reinforce cooler temperatures. There is potential for very isolated, weak thunderstorms along the trough Friday, but instability appears lacking in all models. Although there will be gusty southerly winds aloft, no model shows them mixing to the surface where weak north and west winds will persist. Most long range models show high pressure at least briefly rebuilding this weekend. /JHW && .AVIATION...A thin but persistent marine layer has brought sporadic IFR conditions to coastal terminals throughout the day today. Some sporadic VFR clearing will remain through the early evening, with fog an stratus resurging around sunset. LIFR conditions are most likely (70% chance) by midnight before very slowly lifting again during the day Wednesday. Otherwise, VFR conditions have persisted across the interior except where thick smoke has socked in valleys around the MP18 fire in Hoopa. /JHW & .MARINE...Fresh north winds gusting up to 28kts have persisted across the outer waters today with steep seas up to 10 feet. Winds have been much calmer closer to shore, with gusts only around 12 kts with some seas up to 5 feet pushing in from the outer waters. Some stronger north winds will briefly push into the southern outer waters Tuesday evening and early Wednesday, mostly downwind of Cape Mendocino. Beyond short period seas, a very minor 2 foot, mid period southerly swell is augmenting the sea state. North winds gradually ease through the week with particularly calm conditions int he northern waters by Friday. /JHW && .FIRE WEATHER...Hot and dry weather has peaked today with the hottest valleys reaching near 100 F and some RH values in the upper teens. Thermal belt strength will peak Wednesday morning with poor RH recovery as low as 30 percent along mid and upper slopes. Winds remain weak and terrain driven. Conditions will generally ease through the end of the week with increasing marine influence. Weak transport wind will continue to allow smoke accumulation around the MP18 fire in Hoop and up the Trinity River Valley, creating some extra, localized moderation of conditions. The greatest forecast challenge remains thunderstorm potential around Friday. There is high ensemble confidence that a strong stream of midlevel tropical moisture will push across the area from the southwest early Friday morning and through the day. At the same time, a strong southerly jet forming offshore and aligning with topography could provide and lift and enhance instability to allow for thunderstorms. Even with this dynamic forcing, however, no model is consistently showing any amount of instability. Similar events have generated high clouds and virga, but little to no lightning. There remains a very slight (5%) chance of lightning in northern Trinity and Humboldt Counties Friday morning and afternoon, but coverage would be sporadic and very isolated. Any lightning that does occur will be dry, increasing fire risk. This forecast could quickly change if a source of instability materializes. /JHW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Wednesday for PZZ455. Small Craft Advisory until 9 PM PDT Wednesday for PZZ470. Small Craft Advisory until 9 AM PDT Thursday for PZZ475. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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

071 FXUS66 KMTR 182323 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 423 PM PDT Tue Aug 18 2026 ...New AVIATION, MARINE... .KEY MESSAGES... Updated at 218 PM PDT Tue Aug 18 2026 - Modestly compressed marine layer through midweek - Near normal temperatures through Wednesday followed by a slight cooling - Elevations above about 1000 feet will remain warm overnight && .SHORT TERM... Issued at 218 PM PDT Tue Aug 18 2026 (This evening through Wednesday night) A 500hPa of high pressure anchored over the desert southwest continues to nose into our service area today yielding near normal temperatures for most areas. The exception are area ridges where temps are running a few degrees above this time yesterday. The more interesting part is the relative humidity. RH values at elevation are anywhere from 5 to 20 percent below this time yesterday. For example, the Hastings RAWS (Santa Lucia Range - Monterey County) has an RH of 14% as of 1:11 PM today. At the same time on Monday the RH was 38%. That`s a 24% drop in RH in 24 hours. This is to state that the upper ridge has compressed the marine layer which is allowing for significant drying at elevation. These patterns continue into the night as well and can drop RH into single digits during nocturnal drying events. As the ridge pushes in a touch more tonight expect slightly warmer temps and drier conditions above the marine layer. While the NBM seems to handling the bulk of the near term well, areas above about a 1000 feet were warmed and dried slightly using a blend of NBM and short range high resolution models such as HRRR, RAP, and NAM. For our populated areas conditions tonight through Wednesday night will be a near copy of the previous 24 hours. The coastal areas will see some low clouds and some fog. There may even be some light drizzle in areas like Half Moon Bay, Santa Cruz, and Santa Rosa in pre-sunrise AM hours of Wednesday. && .LONG TERM... Issued at 218 PM PDT Tue Aug 18 2026 (Thursday through next Monday) An upper level area of low pressure has been quasi-stationary over the NE Pacific for the last few day. By the time we get into late week, the upper low is expected to transit Eastward into the Pacific Northwest, pulling an upper trough into the Bay Area. Looking at the WPC Clusters, confidence is high this trough will impact the Bay Area and Central Coast with an onshore push of marine air and a deepening marine layer. This will cause clouds to hang on a little longer in the morning hours and redevelop a little earlier in the late afternoon. The deepening marine layer will also bring higher humidity to areas of elevation. However, surface winds will also kick in with breezy conditions at the coast, in coastal gaps like the Petaluma gap, and over East Bay saddles like Altamont Pass and the Delta. This cuts two ways. One being higher moisture content is good in helping to suppress fire ignitions. Two being the breezy conditions on fully cured fine fuels. If something gets going into the lighter to moderate fuels, it could run with the onshore winds. From a purely sensible weather standpoint, it will simply be pleasant weather all week. The final piece the address in the medium term is mid level moisture advecting over the area late in the week. Model are all over the map with this potential. While the probability is there, confidence remains low as to where the highest PWAT will advect towards. Whenever we see a pattern like this the first thought is high based convection. Looking out as far as possible with higher resolution models, moisture and instability do look to be present, in some current model runs. The limiting factor is cooling aloft. Like we have seen in other similar situations this summer, the lacking ingredient is cooling aloft. This would really turn over the mid layers and could provide deeper convection. However, at this time cooling aloft is not in the cards. As it stands right now we have moisture spreading in Thursday night into Friday (and beyond) with marginally supportive lapse rates during times of highest moisture advection. Even if the vertical development could get going, tapping into the zone to exchange charges and produce lightning has less than a 1% chance at this time. I just don`t see it happening. That said, we`ll need to watch it over the coming days as we get more data. The most we would likely see are some high based convective showers that produce little to no measurable precipitation at the ground. The only other item to watch for during any convective shower activity would be locally gusty winds, especially in the mountains where it will be closer to the base of the storms. && .AVIATION... (00Z TAFS) Issued at 422 PM PDT Tue Aug 18 2026 Currently VFR at all terminals except for HAF which is IFR. Moderate to high confidence in a persistence forecast prevailing with the return of IFR ceilings for most terminals. If the marine layer compresses further, then lower confidence in ceilings reaching LVK and SJC with lower ceilings and visibilities elsewhere. Diurnal winds will prevail. Vicinity of SFO...Currently VFR with gusty northwesterly flow. Moderate (60%) confidence in the return of an IFR ceiling tonight. Diurnal winds will prevail. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Currently VFR with westerly flow at both terminals. High confidence in IFR ceilings returning tonight with periods of LIFR conditions. Diurnal winds will prevail. && .MARINE... (Tonight through next Sunday) Issued at 422 PM PDT Tue Aug 18 2026 A fresh to strong northwest breeze will develop across the outer waters through the night and extend into the inner waters on Wednesday. Winds then remain elevated through the end of the forecast period. Locally stronger winds are possible in the coastal jet regions north of Point Reyes and along the Big Sur coast. Seas build to 7 to 9 feet tonight and into Wednesday before subsiding by the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM Wednesday to 3 AM PDT Thursday for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...BFG LONG TERM....BFG AVIATION...Sarment MARINE...RGass 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

548 FXUS66 KOTX 190005 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 505 PM PDT Tue Aug 18 2026 .KEY MESSAGES... - Breezy, warm conditions lead to elevated to critical fire concerns today. - Warm, dry conditions for the midweek. - Weekend system brings thunder threats and gusty winds increasing fire concerns. && .SYNOPSIS... Increased afternoon winds lead to elevated fire concerns for today. Temperatures increase well above average by Thursday and Friday as high pressure dominates. A pattern change Saturday will bring cooler, unsettled conditions. && .DISCUSSION... Today through Friday: Warm and dry conditions are expected through Friday as an upper level ridge builds. Temperatures will be around the upper 80s to upper 90s through Friday. Today will feature elevated to critical fire weather conditions as surface high pressure in western Washington increases pressure gradients across the Cascades. Fire weather concerns will be maximized across the lower Palouse and Snake River valley west of Lewiston and in the Cascade gaps once downvalley flow dominates in the late afternoon and early evening hours today. Overall expect breezy west winds around 10-15 mph with gusts around 20-25 mph for the Cascade gaps and the lower Palouse/Snake River valley. Thursday and Friday will have elevated fire weather conditions thanks to deep mixing around 700-600 mb and temperatures reaching into the low to mid 90s across the Cascades and northern mountain valleys. Saturday through Tuesday: Ensemble guidance continues to be in good agreement with troughing offshore Friday but the evolution of this into the weekend is muddy at best. Latest EPS/CMC ensembles (70% of the global ensembles) keep the trough west of Oregon and more amplified Saturday, which would favor more chances for thunderstorms across the Inland Northwest. The latest GEFS ensemble (30% of the global ensembles) still brings this trough and associated dry cold front through the Inland Northwest Saturday which favors a drier and windier scenario. Either way, critical fire weather conditions appear likely at this stage as thunderstorms that form in the EPS/CMC environment would be moving fairly quickly to the north with decently strong southerly 500 mb flow around 35-50 kt, increasing the chances for dry lightning. In the GEFS solutions, critical fire weather conditions appear likely with sustained winds around 15-25 mph and relative humidities around 15-25%. Confidence will increase over the next couple of days how this time period will play out. Temperatures behind the front will be knocked down to near normal in the 80s, but the exact evolution behind this trough remains unclear. /DB && .AVIATION... 00Z TAFs: VFR conditions will prevail through the 24 hour TAF period with isolated MVFR vis/cigs due to smoke. Gusty winds will ease overnight to southerly light winds. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence in minimal visibility reductions. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .Preliminary Point Temps/PoPs... Spokane 59 88 56 93 59 93 / 0 0 0 0 0 0 Coeur d`Alene 58 88 57 93 60 94 / 0 0 0 0 0 0 Pullman 50 86 50 92 54 92 / 0 0 0 0 0 0 Lewiston 61 92 62 98 66 97 / 0 0 0 0 0 0 Colville 51 88 50 93 51 93 / 0 0 0 0 0 0 Sandpoint 54 85 53 89 56 90 / 0 0 0 0 0 0 Kellogg 55 85 55 91 58 93 / 0 0 0 0 0 0 Moses Lake 56 89 56 94 59 93 / 0 0 0 0 0 0 Wenatchee 65 90 66 93 69 92 / 0 0 0 0 0 0 Omak 62 91 62 94 64 94 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...Red Flag Warning until 10 PM PDT this evening for Lower Palouse -Snake River (Zone 709). Air Quality Alert until 10 AM PDT Friday for Central Chelan County-Moses Lake Area-Okanogan Highlands-Okanogan Valley- Upper Columbia Basin-Waterville Plateau-Wenatchee Area- Western Chelan County-Western Okanogan County. ID...None. && $$

482 FXUS66 KPDT 182243 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 343 PM PDT Tue Aug 18 2026 .KEY MESSAGES... - Breezy winds and low relative humidity producing elevated to critical fire weather conditions through this evening - Drying and warming trend into Friday as upper level high pressure builds over the region, with elevated fire weather concerns due to dry and unstable conditions - Breezy winds developing Saturday, with uncertainty in timing/extent of thunderstorms/showers Friday through Sunday morning && .DISCUSSION... Visible satellite imagery shows mostly clear skies across the forecast area this afternoon, though several smoke plumes are visible across the Cascade east slopes and in the northern Blue mountains. Meanwhile, water vapor imagery shows an upper low offshore western CONUS while a shortwave trough slides into western MT. The shortwave trough passage through the region has resulted in a strengthening of the cross Cascade pressure gradient today. Breezy gap winds extending into the Columbia Basin will persist through the evening, then decrease with the weakening of the surface pressure gradients overnight. Though several days of thunderstorms moved through the area, dry conditions have settled back into the region, and combined with the breezy winds, will bring elevated to critical fire weather conditions through the evening. Tomorrow through Thursday, upper level ridging will build into the PacNW resulting in a warming and drying trend with light winds. Daytime temperatures will rise into the lower to upper 90s in the lower elevations by Thursday, with Thursday night lows only cooling into the lower to mid 60s across much of the area (cooler in central OR and mountain valleys/basins). Rising lapse rates (and mixing heights) under the upper ridge will bring elevated fire weather concerns across the high terrain, as the combination of dry and unstable conditions may lead to increased fire behavior through Thursday. Friday through Sunday, ECMWF and GFS ensemble members are in good agreement that the upper low offshore western CONUS will become an open wave as it lifts into the PacNW, bringing with it rounds of isolated to widely scattered thunderstorms, breezy to locally gusty winds, and cooler temperatures. However, agreement on timing, intensity, and location are poor. GFS ensemble mean shows it`s members (and the deterministic) favoring the upper trough coming inland late Friday evening and overnight, triggering nocturnal isolated thunderstorms across the forecast area during that time period. Meanwhile, ECMWF members (and it`s deterministic/control) favor a later passage by about 6 to 12 hours, with isolated thunderstorms developing very early Saturday morning across the Cascade east slopes, then late evening thunderstorms developing over the Blues and Wallowa county. Both solutions do favor breezy winds developing through the Cascade gaps Saturday, with ECMWF members favoring stronger winds then those of the GFS members. Forecast confidence is at least moderate (45-60%) in the upper trough passage occurring through the weekend, however there is low confidence (20-25%) in forecast details. By next Monday, there is moderate confidence (55-60%) in upper level ridging building back over the region with dry and warm conditions with light winds. Lawhorn/82 && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... VFR conditions prevail with breezy winds in DLS and PDT. Winds will be generally light at less than 12 knots sustained with elevated smoke in the region. A small chance (5 to 15 percent) exists for some low-level smoke bringing temporary MVFR conditions for all TAF sites. && .FIRE WEATHER...Breezy winds through the Cascade Gaps will overlap with low RH in the OR Columbia Basin, eastern Gorge, and around Warm Springs through this evening. Hot, dry, and unstable conditions will develop Wednesday through Thursday as high pressure builds overhead. Friday into the weekend, there is increasing potential for a return of isolated thunderstorms across the area, with breezy to locally windy conditions through the Cascade gaps and Columbia Basin. Lawhorn/82 && .Preliminary Point Temps/PoPs... PDT 54 90 56 93 / 0 0 0 0 ALW 62 92 63 95 / 0 0 0 0 PSC 57 92 56 96 / 0 0 0 0 YKM 59 92 61 96 / 0 0 0 0 HRI 59 92 59 95 / 0 0 0 0 ELN 59 88 59 92 / 0 0 0 0 RDM 47 91 50 94 / 0 0 0 0 LGD 53 93 56 97 / 0 0 0 0 GCD 55 95 57 99 / 0 0 0 0 DLS 60 91 61 96 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... WA...None. OR...Air Quality Alert until 1 PM PDT Wednesday for ORZ041-505-506- 509>511. Red Flag Warning until 10 PM PDT this evening for ORZ691-701- 703. && $$ DISCUSSION...82 AVIATION...95 FIRE WEATHER...82

653 FXUS65 KREV 181902 AFDREV Area Forecast Discussion National Weather Service Reno NV 1202 PM PDT Tue Aug 18 2026 .KEY MESSAGES... * Dry and warm conditions through Thursday across the Eastern Sierra and western Nevada. * Breezy conditions are expected each afternoon, with stronger winds possible Friday into the weekend. * Shower and thunderstorm potential returns by Friday for the Eastern Sierra of southern Mono county. && .DISCUSSION... Afternoon highs peak Wednesday and Thursday, topping out near 100 for lower valleys and mid to upper 80s for Sierra communities. A cooling trend will welcome the weekend, with highs dropping to the low 90s for W NV and lower valleys, and low 80s for the Sierra. This will be contributed to a dome of high pressure propagating eastward. With the high moving eastward, and a trough off the California coast tracking northeastward and inland, this will increase our daily afternoon breezes Friday and Saturday. Expect widespread gusts up to 30 mph, locally higher in wind prone areas and along the higher terrain. These enhanced winds coupled with dry fuels in NE CA and NW NV will produce a handful of elevated to critical fire weather conditions both days. Monsoonal moisture will also move its way into the area this weekend, increasing the chances for afternoon showers and thunderstorms. At this time, the best chances (15-20%) will be in southern Mono, southern Lyon, Mineral, and eastern Churchill counties Friday through at least Sunday. While this seems to be a similar pattern to what we had last week, there is less moisture this time around; storms will be more isolated in nature, with the main concern being strong outflows and lightning. -Giralte && .AVIATION... VFR conditions continue through much of the week with typical breezes up to 20 kts. Lower CIGS/VIS for KMMH by Friday with afternoon shower and thunderstorm development (15-20% chance). Otherwise, breezes increase to 30-35 kts for all terminals Friday and Saturday. -Giralte && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

237 FXUS66 KSTO 181918 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1218 PM PDT Tue Aug 18 2026 .KEY MESSAGES... - Elevated Fire Weather Conditions Friday through Saturday within the Burney Basin due to low RH and breezy westerly winds. - Dry and seasonably warm through the week and into the weekend. && .DISCUSSION... Current synoptic pattern aloft has a ridge of high pressure across the four corners of the United States, with southwesterly flow over California. Satellite/observations have sunny conditions this afternoon, with temperatures hovering in the 80s to lower 90s. Highs will be in the 90s today within the Valley and portions of the foothills, with lower 100s in the northern Sacramento Valley. Cooler conditions as you head further into the mountains. Warmest conditions are expected today through Friday, but trend cooler over the weekend and into next week. A weak trough moves along the ridge Thursday and Friday bringing lift to portions of northern California. Looking at soundings, we have weak synoptic support, little moisture content, and lacking instability to develop chances for showers and storms. Instability is slightly higher toward the Shasta-Trinity area and there is a very low chance (less than 5 percent) for a quick storm to develop in the afternoon/evening hours both Thursday and Friday. None the less, there will be enough forcing to bring clouds to Interior Northern California Thursday through Friday. As the system moves through the region, winds become breezy through the Delta and into the Burney Basin. Delta winds gust up to 20kts during the evening hours helping to cool off temperatures and increase RH values. In the Burney Basin the already dry RH values in the upper teens to mid 20s range combined with breezy downsloping westerlies bring elevated fire weather concerns both Friday and Saturday. We will continue to monitor the fire weather conditions for the Burney Basin end of the week and into the weekend. Otherwise, looking behind the weekend conditions look to remain dry as the ridge remains locked into place. && .AVIATION... VFR conditions continue through the TAF period, with breezy onshore winds within the Delta and portions of the Sacramento Metro this evening. A few gusts to 20kts in the Delta this evening. SCT to BKN clouds move in around 04-08z and continue through 18z for the Sacramento sites, MOD, and SCK. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

916 FXUS65 KMSO 181838 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1238 PM MDT Tue Aug 18 2026 .DISCUSSION... KEY MESSAGES: - Shower and thunderstorm activity will continue this afternoon. - Ridge of high pressure Wednesday through Friday causing warming and drying. - Increased atmospheric moisture leading to a return to active weather Friday onward. A disturbance moving through the Northern Rockies will interact with a drier air mass. Thunderstorms will not be widespread but areas that may see isolated storms will be along the Continental Divide, especially Silver Bow County and east of the Divide. Due to drier air mixing down to the surface the main threat will be strong outflow winds, with a 5% or less chance of a storm attaining severe strength (wind gusts in excess of 58 mph) in the vicinity of Silver Bow County. The driest day of this air mass change will be Wednesday as relative humidities lower into the teens. Please exercise caution with any outdoor flames and consult local government as many locales have instituted some level of burn ban. This air mass will also produce a warm up with Thursday and Friday being the warmest days of the forecast period. Hells Canyon ID, temperatures will warm 105 to potentially 110F during this period, so take it easy with those outdoor activities. Elsewhere, its not much better with widespread 90s. A trough will deepen off the west coast, pulling up a tropical air mass on Friday into the weekend. Expect relative humidities to increase. The question now becomes at what level in the atmosphere will the moisture reside. Currently, most of the moisture will be high based, so is the response simply clouds and cooler (current forecast), some showers forced by the mountains, or widespread precipitation. This answer will likely come into focus as high resolution models have some input, 72-hours or less from the system. A return to daily afternoon thunderstorms is a most likely solution, Sunday through Tuesday, with some question as to the extent of coverage. && .AVIATION...A disturbance will be moving through the Northern Rockies today. A few showers are developing across northwest Montana which could have an impact at KGPI. After 18/2000z, more showers and thunderstorms will develop mainly across northwest and southwest Montana. Unlike previous days these storms will be capable of strong outflow winds which could impact area terminals. KGPI, KBTM and KSMN have the best potential to be impacted by these storms this afternoon and evening. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

300 FXUS65 KBOI 182326 AFDBOI Area Forecast Discussion National Weather Service Boise ID 526 PM MDT Tue Aug 18 2026 .UPDATE...Updated aviation discussion. && .KEY MESSAGES... - Temperatures warming through the end of the week with lower elevations around 100 degrees Thursday and Friday. - Increased chance of showers and thunderstorms over higher terrain this weekend and into next week. && .SHORT TERM /Through Thursday Night/... Issued 232 PM MDT TUE AUG 18 2026 A ridge of high pressure will continue to build into the region through the work week, bringing a steady warming and drying trend. Clouds have decreased across most of the region today, with a scattered cumulus build ups over high terrain in Central Idaho and near the ID-NV border. A few virga showers will continue near the ID-NV border through the evening, otherwise mostly clear and warm conditions will continue. Temperatures will increase to about 8-12 degrees above normal by Thursday, with lower elevations reaching near or slightly above 100F. A push of monsoon moisture will primarily stay to our south on Thursday afternoon, although there is a low chance (10-20%) of showers and thunderstorms over the Magic Valley late Thursday. Rainfall accumulations will be minimal with any thunderstorms that form, so gusty outflow winds and lightning are the primary concerns. && .LONG TERM /Friday through Tuesday/... Issued 232 PM MDT TUE AUG 18 2026 Southerly flow aloft brought about by the offshore Pacific low pressure system and the Four Corners upper-level ridge will keep temperatures hot on Friday. Another day of 100 degree heat to lower elevations is expected. The upper-level trough will move inland late Friday into Saturday, moving through the Interior NW on Saturday. Cooling aloft and increased moisture will support a 20-30% chance of showers and thunderstorms across higher terrain of e-central Oregon and SW Idaho Friday, shifting to mostly SW Idaho for Saturday and Sunday. Temperatures will be cooler behind this disturbance, lowering to near-normal Saturday and Sunday. Long-range models hint at the Four Corners ridge rebuilding over the area early next week with temperatures warming again. The real question will be moisture early next week; some models show a strong surge with high precipitation chances and QPF totals, while others show a more limited scenario. The current forecast shows somewhere in the middle, with a 10-30% chance of showers/storms over SW Idaho. && .AVIATION /00Z Wednesday through Thursday/... Issued 520 PM MDT TUE AUG 18 2026 VFR with scattered cumulus over most areas. Isolated showers/thunderstorms continuing north and east of KMYL and higher terrain south of KTWF through around Wed/03Z. High density altitude in hot afternoon temperatures through sunset. Patchy smoke near KBKE and KMYL late tonight through Wednesday morning. Surface winds: W-NW 5-15 kt, becoming NW or variable under 8 kt tonight. Winds aloft at 10kft MSL: W 5-20 kt. KBOI...VFR with mostly clear skies. Surface winds: NW 6-10 kt this evening, becoming variable under 7 kt after sunset. && .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 AVIATION.....JY SHORT TERM...SA LONG TERM....CH

409 FXUS65 KLKN 181928 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1228 PM PDT Tue Aug 18 2026 .KEY MESSAGES... * Warming trend through Thursday * Moderate to Major Heat Risk for Thursday * Chances for monsoon storms return starting Saturday && .DISCUSSION... (This evening through next Monday) WEATHER PATTERN OVERVIEW: Upper level ridging continues to expand over the desert southwest, with dry and warming conditions as a result. An isolated thunderstorm or two cannot be completely ruled out for tomorrow and Thursday, but odds are around 5% at most. Temperatures are expected to climb as the ridge takes hold, peaking on Thursday with highs in the upper 90s and triple digits possible along the I-80 corridor. Heat Risk during this period will be in the Moderate range, with some Major sprinkled in and a Heat Advisory may be required for portions of northern Nevada on Thursday. After Thursday the ridge is expected to shift back east again, leaving southerly to southwesterly flow over Nevada. This would reopen monsoonal moisture flow and bring yet another wave of monsoonal thunderstorms to the forecast area by the weekend. High temperatures are also expected to return to the more seasonal low 90s for the weekend and into early next week. FORECAST CONFIDENCE & DEVIATIONS: High confidence in dry and warming conditions through Friday. Moderate confidence in returning monsoon conditions this weekend and early next week. No changes to NBM output. && .AVIATION...Light winds and VFR conditions expected through the next 24 hours. && .FIRE WEATHER...Elevated conditions through Friday due to breezy afternoon winds and dry and warming conditions. Some locally critical wind potential is being watched for this weekend but returning monsoon flow may increase humidity enough to negate fire weather concerns. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...94 AVIATION...94 FIRE WEATHER...94