Graphical Hydro Meteorological Discussion

144
FXAK68 PAFC 181242
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
442 AM AKDT Fri Jul 18 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3: Today through Sunday)...

The underlying pattern is not slated to change much this weekend
as much of Southcentral continues to see a mix of clouds and sun
along with seasonably warm temperatures through early next week.
This morning, an upper level trough is moving from the Alaska
Peninsula up into the greater Cook Inlet and Mat-Su region,
spreading mostly mid to upper level cloud cover into all but the
Copper Basin. Farther south, a weak low is developing just south
of Kodiak Island along a slow moving frontal boundary lifting up
into the southern Gulf. Similar to the last system a couple days
ago, rain associated with the incoming front is very unlikely to
reach just about any part of the Southcentral interior.
Measurable rainfall will be confined mostly to the southern end
of the Kenai Peninsula and Kodiak Island today as the upper level
trough outruns the already weak Gulf low and front, which will
cause the system to dissipate and lose upper level support well
before it can make any headway past the Gulf coastline. Southerly
gap flow will develop out of the Copper River Valley and Turnagain
Arm today, but given the upper cloud cover and very weak coastal
gradient, expect gap winds in both locations to remain fairly
light today.

From Saturday into Sunday, the northern periphery of a Pacific
ridge will build into the southern Mainland, extending the already
relatively warm and dry conditions for much of the region. The fly
in the ointment hinges on the exact timing and trajectory of a
series of weak shortwaves that could eject from a large Bering
Sea low and ride around the ridge axis. Any stronger shortwave
that can reach our area will threaten to bring periods of light
rain at times for mainly the western half of Southcentral,
particularly towards Sunday afternoon. However, it`s quite
plausible that (just like what we observed with the past two
disturbances) precipitation will fail to make it much past the
Cook Inlet and Kenai Peninsula as supporting lift weakens while
the upper ridge remains the dominant influence on surface
conditions. Regardless of any rain chances, expect valley
temperatures to become quite warm both Saturday and Sunday, with
much of Anchorage and the Mat- Su Valleys approaching 70F for
highs. In fact, parts of the Copper Basin could even hit 80
degrees on Sunday afternoon.

-AS

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(Days 1 through 3: Today through Saturday)...

A quasi-stationary, occluded Bering Sea low located roughly 275
miles north of Amchitka will continue to steer multiple waves of
moisture and smaller low pressure systems into the Aleutians,
Alaska Peninsula and Southwest Mainland through the end of this
weekend. There is also a more compact low pressure system
skirting just to the south of the Aleutian chain. Aloft, the flow
around the Bering low is rather disorganized and noisy as multiple
vorticity waves are being advected from the North Pacific, across
the Aleutian chain, and into the Bering.

This morning, a fast moving low pressure system situated between
Chignik and Kodiak Island is quickly moving out of the region and
into the Gulf of Alaska. Showers are expected to continue for a
few more hours for the northern AK Pen and Kuskokwim Valley as the
system departs.

Due to the low formation south of the Central Aleutians, a stout
southerly wind fetch has developed and is moving across the
Eastern Aleutians, with small craft conditions expected for Dutch
Harbor and Cold Bay. Friday afternoon to Saturday evening,
southerly winds return for Bristol Bay as the low pressure system
and its front move eastward. There is the likelihood of a
prolonged period of onshore winds early Saturday afternoon through
the late evening hours for the Southwest Mainland coast. The
current thinking for precipitation is that an axis of moisture
will move inland into the Kuskokwim coast and Bristol Bay areas,
and then pushing more so into the Southwest interior on Saturday.
As this low departs Sunday, widespread showers are expected across
the Aleutians, Alaska Peninsula and Southwest Mainland.


-AM/DJ

&&

.LONG TERM FORECAST (Days 4 through 7: Monday through
Thursday)...

By Monday, the pattern will be initially directed largely by a
weakening low pressure system over the northwestern Bering Sea and
a large ridge developed over the southern Gulf of Alaska.
Southwesterly flow across southern Alaska will persist due to the
orientation of the aforementioned pressure system. This flow
pattern will keep Southwest Alaska likely moist with plenty of
cloud cover with air continuing to flow in from the Bering Sea.
Through mid-week, the weak low in the northwestern Bering will
dissolve, leading to the pattern being lead by the ridge in the
northern Pacific. Shortwaves coming up and over the ridge will
maintain the unsettled pattern along the Alaska Peninsula and into
Southwest/Southcentral mainland Alaska.

-CL

&&


.AVIATION...

PANC...VFR conditions will persist. Light winds this morning
become southeasterly with gusts of 15-20 kt this afternoon and
evening, then diminish overnight. Ceilings may drop to around
4000 ft early this morning but should increase above 5000 ft by
late morning.

&&


$$

731
FXAK69 PAFG 182230
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
230 PM AKDT Fri Jul 18 2025


.SYNOPSIS...A storm system will spread moisture in a southwest
flow aloft over the Interior for the next week. The western
Interior and west coast will receive occasional rain during this
time. The remainder of the Interior and Brooks Range will receive
scattered showers and isolated thunderstorms...until more
widespread rain moves up around next Wednesday and Thursday. Highs
will be in the 70s this weekend. The Arctic Coast remains colder
with gusty east winds and areas of fog Saturday...but warms into
the 50s again by Sunday.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...

- High temperatures mainly in the 70s with light winds through the
weekend. Skies will be partly cloudy.

- Scattered showers and isolated thunderstorms mainly over the
higher terrain this weekend.

West Coast and Western Interior...

- Occasional rain Saturday night and Sunday mainly west of a Huslia-
McGrath line. Scattered showers elsewhere.

- Winds mainly offshore and 15 mph or less along the coast through
Sunday. Gusty south-southwest winds on Monday.

- Temperatures remain steady for Saturday...60s near the west
coast...70s in the Interior. Temperatures cool Sunday and
Monday.

North Slope and Brooks Range...

- East winds 20 to 35 mph along the Arctic coast Saturday...
decreasing to 10 to 20 mph Sunday.

- Scattered showers and isolated thunderstorms mainly over the
Brooks Range this weekend.

- Gradual warming Sunday into Tuesday. Highs in the 50s and low
60s along the coast...with 70s possible in the Arctic Plain.

&&

.FORECAST ANALYSIS AND DISCUSSION...Shortwave energy in a
moist southwest flow aloft will trigger scattered showers and
isolated thunderstorms over the higher terrain of Interior the
next several days. Lightning activity is expected to be minimal
this evening but more than yesterday. Isolated thunderstorm
formation is favored over the Fortymile country and eastern
Alaskan Range. Storms will spread up into the Brooks Range this
weekend. More widespread light rain will occur roughly west of
Huslia-McGrath line later tonight into Sunday. High temperatures
this weekend will be in the 70s except for 60s along the west
coast with the clouds and rain. The Arctic Coast remains colder
with gusty east winds and areas of fog Saturday... but warms into
the 50s again by Sunday.

&&

.FIRE WEATHER...
Temperatures this weekend will remain slightly above normal, with
southwest flow on Saturday bringing stratiform rain over the West
Coast and Western Interior; chances for thunderstorms hang on
across parts of the Interior and even the North Slope. Southwest
flow looks to continue into next week, bringing more rainfall and
cooler temperatures into the Interior. RHs look to remain plenty
wet in these patterns, mainly above 40% with a few readings in the
30-40% range possible across the Upper Tanana Valley each day
through Sunday. Northeast winds will gust to 15 mph across the
Yukon Flats Friday afternoon through Sunday. Southerly gap winds
will gust to 30 mph through Alaska Range passes on Sunday.

&&

.HYDROLOGY...No concerns at this time. We will monitor potential
flash flooding from the day 3-7 hazardous rainfall projections by
WPC .


&&

EXTENDED FORECAST DAYS 4-7...There is good model agreement that a
low will move over the Bering Sea by Sunday...and then up near
the Bering Strait by next Tuesday. The high pressure ridge is
pushed east over the Canadian Yukon and breaks down. A series of
shortwaves will rotate around this low and move up over the
Interior in a moist west-southwest flow. Hazardous rainfall
remains possible on Tuesday over the Brooks Range...and along the
Denali Park Road and north side of the Alaska Range west of the
Parks Highway. Ensemble solutions want to move the Bering low
energy down over the Interior the middle of next week. The cold
frontal boundary forcing will result in widespread rainfall as it
tracks east. Hazardous rainfall will also be possible Wednesday
and Thursday over the eastern Alaska Range and Fortymile country.
This is a wet pattern that will likely settle down our wildfire
activity even more. Even the Yukon Flats could see some widespread
rain late next week.

Coastal Hazard Potential Days 3 and 4...None

&&

.EXTENDED FORECAST DAYS 4-7...
Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ801-850-851.
Small Craft Advisory for PKZ802.
Small Craft Advisory for PKZ812-815-858.
Small Craft Advisory for PKZ813.
Small Craft Advisory for PKZ814.
Small Craft Advisory for PKZ816.
Brisk Wind Advisory for PKZ859.
Brisk Wind Advisory for PKZ860-861.

&&

$$

Maier/Park (FWX)

288
FXAK67 PAJK 182318
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
318 PM AKDT Fri Jul 18 2025

.SHORT TERM.../Through Saturday night/ Fairly quiet conditions
across the panhandle with dry weather and mostly mid level clouds
across a wide area of the panhandle (lots of sunny breaks around
Kuiu Island, Western Prince of Wales, Ketchikan, Annette Island,
and Misty Fjords). It is these clouds that have kept temperatures
in the upper 50s to low 60s for the most part this afternoon so
far while areas that are seeing some sun have temps reaching into
the mid to upper 60s. As of 1 pm, some breaks in the clouds are
starting to appear across the northern inner channels, but they
are being slow to develop.

Quiet conditions are expected to continue as ridging over the gulf
strengthens. The question is how long the cloud cover will stick
around. Wind streamlines suggest that flow will remain slightly
onshore into Cross Sound into Saturday at least so clouds around
Icy Strait, Peril Strait, and possibly further inland will stick
around into Saturday. However, low level flow looks to start to
turn just enough offshore by late Saturday that northern inner
channel areas may see more breaks in the cloud cover come Saturday
afternoon. This also means that expected high temperatures for
Saturday will be a little warmer then what was seen today. For the
southern panhandle flow is mostly offshore through the period so
more substantial breaks in the cloud cover is expected with
corresponding higher afternoon temps.

Winds are mostly 15 kt or less today and are expected to stay that
way. The only things that may break that pattern are the usual sea
breeze circulations that develop in the afternoons and evenings.
Especially if any substantial sunny breaks develop which could
produce some sea breezes up to 15 to 20 kt in localized areas.

.LONG TERM.../Sunday through Thursday/...A surface high pressure
system in the southern Gulf of Alaska continues to build through
the week, stalling over the southwestern gulf due to broad upper
level ridging. This ridging will funnel more dry air over the
panhandle, continuing the warming and drying trend into the long
term. Multiple approaching shortwaves in the gulf attempt to
strengthen through the weekend which could increase chances for
light precipitation along the northern gulf coast, though all look
to break apart before reaching the outer coast. The surface
ridging continues to strengthen into early next week which will
clear out skies and tighten the pressure gradient, increasing wind
speeds along the gulf coast. By Monday afternoon, sustained winds
will increase to 20 kts going into cross sound, with highest
speeds reaching around up to 30 kts off the southwestern coast of
PoW. Gusts may reach 30 kts in Dixon Entrance. A tightening
pressure gradient will bring up wind speeds from the northwestern
gulf, and an ESE direction is conducive to gap winds coming out
from between Kodiak Island and the Kenai Peninsula. From this, the
central gulf can expect to see up to 30 kts of westerly winds
with wave heights reaching 13 ft through Tuesday. The consistent
NW upper-level winds help to pull a deep upper-level trough down
over the panhandle Wednesday afternoon. This will assist the
associated surface shortwave trough in strengthening to a weak,
closed low over the northern gulf coast, bringing precipitation
back into the forecast for Thursday.

Clearing skies will allow for a sea breeze to develop in some of
the inner channels, with winds potentially reaching 10 to 15 kts
near the water in Juneau, Haines, and Skagway. Stronger winds are
expected through Icy Strait and up Lynn Canal with this sea
breeze, peaking in the mid afternoon. This is also conducive to
marine layer development along the gulf coast which will bring low
clouds to coastal regions and pushing into Cross Sound.

High temperatures of between 13 to 15 degrees C at 850 mb with
areas of 16 degrees C and clearing skies indicate warmer surface
temperatures for early next week, raising for Monday and peaking
Tuesday. Interior regions of the panhandle will experience the
highest temperatures, with highs potentially reaching the mid to
high 70s and lows in the mid 50s. Max temp EFI values have stayed
consistently high Monday through Wednesday. NBM probabilities are
indicating a 60% potential of reaching 80 degrees in areas of
Skagway and Haines and an 80% potential in Hyder on Tuesday. These
are areas of known temperature biases for the NBM and other
models are only estimating around a 30% chance just for Hyder, so
confidence is very low on temperatures actually breaching 80.

&&

.AVIATION...Mid level clouds across the panhandle and the gulf
coast waters. A ridge of high pressure over the gulf keeps an
onshore wind flow. The north Lynn Canal is a bit out more
scattered clouds. Most clouds this evening in the 3500 to 5000 ft
ceiling range. Likely will see them staying the same, or lowering
to 2500 to 3500 feet. Saturday the southern half the of the
panhandle should start to see breaks developing in the clouds.

&&

.MARINE...Inside waters: Wind conditions are rather low with 15 kt
or less observed in most areas, and with the exception of Lynn
Canal, wind directions are mainly N or W. Not much change expected
over the next few days in the inner channels with mainly N and W
flow with speeds of 15 kt or less and seas of 3 ft or less. The
main exceptions will be areas with strong sea breezes, like near
Skagway, and Cross Sound, where 20 kt winds could be seen during
the afternoons and early evenings.

Outside Water: W to NW flow is the main wind direction in the
gulf today and that is mainly expected to remain the case for the
next few days. Highest winds are around 15 kt off Prince of Wales
Island and in the central gulf. Combined seas are around 4 ft
with most of that being a 3 to 4 ft SW swell of 8 sec period.
These conditions are not expected to change all that much through
the weekend as ridging settles into the gulf. Highest winds
(around 15 to 20 kt) will mainly be off the western coast of
Prince of Wales Island through the period.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

SHORT TERM...EAL
LONG TERM....ZTK
AVIATION...Bezenek
MARINE...EAL

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