Graphical Hydro Meteorological Discussion

909
FXAK68 PAFC 231210
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
410 AM AKDT Fri May 23 2025

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

An occluded front over the Gulf of Alaska this morning continues
to slide south as a transient ridge of high pressure builds across
Southcentral. Conditions are generally clear and dry over the
Copper River Basin this morning with temperatures in the 30s. To
the west, mid-level clouds linger across the Mat-Su south to the
Kenai Peninsula; however, this area of cloud cover is diminishing
as it drifts west to the Alaska Range.

The main weather feature of concern today will be an upper-level
wave over the Yukon this morning. This feature will move across
the Copper River Basin today and into the northern Gulf this
evening. Increasing moisture and instability with this feature,
along with daytime temperatures pushing into the 60s, will lead to
the development of widespread showers and isolated wet
thunderstorms from the Copper River Basin southwest to Prince
William Sound through the day today. The best chance for
thunderstorms will likely be from Mentasta Lake and Paxson west to
Eureka and Lake Louise.

The southeasterly gap winds of the past couple of days will be
replaced with sea breezes for coastal locations this afternoon and
evening. Showers will also come to an end by late tonight as the
aforementioned wave moves over the coastal waters.

A secondary wave moving over interior Southcentral Saturday will
being renewed chances for showers and isolated thunderstorms to
portions of the Copper River Basin and northern Susitna Valley.
Winds Saturday will remain light, with coastal sea breezes during
the afternoon and evening hours. Given breaks in cloud cover and
light winds, temperatures across the region will be on an upward
trend with many locations well into the 60s to start the weekend.
Anchorage may finally see its first official 60 degree day by
Saturday.

-TM/AM

&&


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

A transient high pressure ridge moves across the Bering Sea
towards Southwest Alaska through tonight. Light lingering rain
showers are expected through this afternoon for the southwest
Mainland that should taper off tonight as the weak ridge passes
through. Out west, a large, gale force low moves into the western
Bering Sea. The associated front moves over the Western Aleutians
this morning, bringing rounds of rain showers and gale force
winds. The front weakens as it tracks across the Aleutians, with
winds remaining below gale force as it moves east of the Central
Aleutians, though rain is expected to track as far as the
Southwest Coast through the weekend. There will be an area of
colder air filtering along the backside of the low that will allow
gale force winds to continue across the Western Aleutians through
Saturday night. Winds are expected to diminish to small craft
Sunday morning and below small craft by Sunday afternoon.

&&


.LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)...

A broad upper level low stretches from Siberia across the Bering
before angling into the Gulf of Alaska. Several shortwaves help
the low centers slip through the pattern as the low becomes more
organized over the Eastern Bering and Western Mainland by the end
of the forecast period. The most persistent low anchors over the
Gulf of Alaska through midweek. Models favor the GFS through the
new week maintaining strengths and tracks of features.

Lingering showers are expected over the Southern half of Mainland
Alaska through Wednesday. A rain-wrapped low and front pushing
across the Central Aleutians and Bering brings moderate rain and
locally gusty winds into the Alaska Peninsula and Southwest Alaska
through Monday. The low sweeps into the Gulf of Alaska, spreading
the rain into Southcentral Alaska and North to the Alaska Range
until Wednesday. Snow is expected over higher elevations,
diminishing Tuesday. In the West, a well developed North Pacific
low and front does a drive-by over the Western and Central
Aleutians for Tuesday and Wednesday before curving back into the
North Pacific.

- Kutz

&&

.AVIATION...

PANC...VFR conditions are anticipated through the TAF period. A
westerly sea breeze will develop in the early afternoon and
persist through the evening hours before diminishing overnight.

&&


$$

161
FXAK69 PAFG 232352
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
352 PM AKDT Fri May 23 2025

.SYNOPSIS...An easterly wave pattern setting up will bring
increasing chances for thunderstorms across the Interior along
with areas of heavy rain this weekend. An arctic trough swinging
south from the Chukchi Sea will enhance this activity and also
bring light snow to the North Slope and Brooks Range. The West
Coast will be spared from most of the action with mostly dry
conditions and a warming trend through the weekend.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
-Warming trend through the weekend. Highs increase to near 70
this weekend for Interior valleys.

-Isolated thunderstorms this afternoon south of the Yukon River.
Thunderstorms increase in coverage on Saturday with widely
scattered storms from Northway to Chicken and isolated storms
south of the Yukon River. Sunday will bring widely scattered
thunderstorms east of Fairbanks.

-Showers and thunderstorms Friday through Monday may produce very
heavy rain. See Special Weather Statement for details. The area
of biggest concern is from Delta Junction to Tok along the Alaska
Highway.

West Coast and Western Interior...
-Warming trend through the weekend. Highs near 60 in the Western
Interior today increase to the low to mid 60s this weekend.

-Mostly dry conditions expected through the weekend except near
thunderstorms in the southwest Interior northeast of Holy Cross.

North Slope and Brooks Range..

-Winds become westerly behind the arctic front passage on Sunday.

-Areas of low stratus persist through the weekend.

-Light snow accumulations Saturday through Monday, mainly 1-2"
from Umiat east, though up to 4 inches is possible through Atigun
Pass and at Kaktovik.

&&

.FORECAST ANALYSIS AND DISCUSSION...A significant pattern shift is
underway with a low in the Gulf of Alaska beginning to move
shortwaves from the east into the Interior as an Arctic trough
swings south from the Chukchi Sea. These features will interact
and set up a favorable pattern for slow moving thunderstorms and
very heavy rain over the Central and Eastern Interior this
weekend. Not all areas will see rainfall and/or thunderstorms, but
rainfall with these storms will be heavy enough to cause concern
for rapidly rising creeks and streams, especially near steep
terrain.

Models are in okay agreement on the overall pattern shift, but
have very high uncertainty on the details. Models have overall
slowed down the progression of the arctic trough from east to
west, which will prolong the length of unstable conditions over
the area. Thunderstorms may persist all night Sunday night into
Monday morning across the eastern Interior with the heaviest
precipitation likely Monday morning east of Delta Junction.


&&

.FIRE WEATHER...A number of easterly wave events will bring
increased thunderstorm activity to the Interior this weekend.
Expect widely scattered thunderstorms from Northway to Chicken
on Saturday and from Fairbanks to Circle to Eagle to the Alcan
Border on Sunday. Isolated thunderstorms are expected both days
across most of the rest of the Interior. These storms will be
exceptionally wet and have the potential to drop very heavy rain
as they will be nearly stationary with very little storm motion.
Thunderstorms may persist all night Sunday night into Monday
morning east of Dot Lake. Temperatures will rise to near 70 in
warm valleys on Sunday, then gradually cool heading into next week
as an Arctic trough passes from west to east, which will
stabilize conditions. Minimum RH will remain 30% or better through
the short term and the extended. Next week will bring more chances
for scattered thunderstorms, though these look very wet as well.

&&

.HYDROLOGY...Degraded ice remains in place at the mouth of the
Yukon River. Snowmelt has begun in the Porcupine watershed in
Canada and water is starting to pool on the ice of the Porcupine
River. Between the border and the Yukon River ice is degrading
with some areas opening up. Breakup has begun on the Kobuk River.
The river broke up at Shungnak on or around May 16th with no
issues. Ice remains in place at Ambler and water levels are slowly
starting to rise as the ice decays in place.

Creeks and streams in the eastern Interior may rise rapidly under
areas of heavy rain Friday through Monday. Rising freezing levels
on Sunday will allow snowmelt from high terrain above Cathedral
Rapids and Sheep Creek along the Alaska Highway to add to rainfall
in those streams. This may cause very high water in these streams
along the Alaska Highway.

&&

.EXTENDED FORECAST DAYS 4-7...Active weather will continue across
the central and eastern Interior through next week with multiple
rounds of heavy showers and thunderstorms expected. The best
chance for a significant event looks to be Wednesday and Thursday.
The North Slope will continue to see intermittent light snow
showers as low pressure remains in the area. The West Coast will
see mainly dry and quiet conditions.

Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...None.
&&

$$

Chriest

762
FXAK67 PAJK 232350
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
350 PM AKDT Fri May 23 2025

.SHORT TERM.../Through Monday morning/ Low center continues to
spin in the Gulf located to the southwest of the panhandle and
gradually moving eastward. This low has brought a front across the
southern panhandle this afternoon, and will continue to linger in
the eastern Gulf through this weekend. It will bring us waves of
moisture throughout this weekend, the next wave pushing up through
the southern panhandle tonight into tomorrow morning. The largest
amounts of QPF will be for the southern panhandle, with moderate
to heavy rain rates of 0.10 inches per hour expected between 09Z
and 21Z on Saturday for Ketchikan and southern POW. The majority
of the high res models as well as the NBM show confidence in QPF
values of 0.60 to 0.80 inches of rain per 6 hours tonight into
Saturday morning for these locations. Lower QPF values and rain
rates are expected for the central and northern panhandle as the
system moves northward tomorrow morning through the afternoon. The
next waves pushing through Sunday morning into Monday morning
will be lighter in amounts of rain and intensity and the low
begins to weaken along the coast.

.LONG TERM...Looking towards the weekend and next week, the rainy
weather looks to stick around for several days.

Key points:
-Moderate to heavy rain expected in the panhandle beginning
Saturday. Lighter rain Monday, heavy rain returns Tuesday and
Wednesday.
-Stronger-than-normal southerly winds will move into the southern
panhandle.

Details:
The southern portions of Alaska will continue to remain rather
unsettled given the time of year with periods of rainfall likely
each day from the Kenai Peninsula eastward to the southeast
Panhandle region. A weakening low pressure system this weekend
will give way to an incoming low from the Bering that will set up
over the central Gulf through the middle of next week, with moist
onshore flow.

Rainfall greatest coverage and intensity is expected from Icy
Strait to the southern Panhandle. A heavy rain area remains
depicted in the WPC medium range hazards graphic for the 25th to
the 28th, given how late in the season this is, and the duration
of the rainfall expected. The highest rainfall is likely to be
south of the Sitka area based on the latest model guidance.

The EFI tables give the greatest amounts of rain from Monday
afternoon into Wednesday night. Not only are the models showing
high confidence of elevated amounts of rain, there is a Shift of
Tails of near 1 to 2 - which tells us that this is an extreme
event for this time of year. For Ketchikan, there is high
confidence (>60%) chance of getting at least 2 inches of rain
over 24 hours beginning Monday afternoon. And it`s a similar story
for areas around Prince of Wales Island and for Metlakatla.

For wind speeds, the EFI is highlighting stronger-than-normal
southerly wind speeds Saturday through mid-week. Marine wind
speeds in the southern inner channels could get upwards of 20 to
35 knots with the strongest speeds found in southern Clarence
Strait and in the outside waters.

&&

.AVIATION.../ 00Z TAF set / Widespread VFR conditions continue across
the panhandle Friday afternoon, with some CIGs below 3000 ft for isolated
showers. These should continue to diminish through the evening ahead
of an approaching system, with winds shifting to more southeasterly
and then easterly at elevation.

Main aviation concern remains deteriorating conditions Friday evening
with a front impacting the southern panhandle. Showers and lowered CIGs
will move in between 10z and 18z along with LLWS of 25 to 30 kts as the
front pushes inland. MVFR conditions
along with LLWS and gusty surface winds will be in store for the
southern panhandle from Frederick Sound southward for a majority of
early Saturday. North of Frederick Sound, primary aviation impacts
will be lowered CIGs and stray showers rotating northward through
the day Saturday.

&&

.MARINE...
Outside: The a gale front increases winds and waves for the gulf
Saturday morning. Late Friday night into Saturday morning,
southerly winds across the southern gulf increase to 25 to 35 kts.
There is an 80% chance that wind gusts will reach strong gale
force of 40 to 45 kts for these southern areas. At this time on
Saturday, wave heights will build to 14 ft west of POW and over N
Dixon Entrance. Expect winds to diminish down to a fresh to
strong breeze Saturday afternoon and continue through Sunday.
Looking towards next week, there is early indications of a
stronger system moving into the panhandle. At this time, expect at
least gale force winds in Dixon entrance and Clarence Strait.
These winds up to 30 knots look to extend as far north as Yakutat.
Certainly an unseasonably strong system.

Inside: The strong front makes its way to the panhandle Saturday
increasing southern channels to near gale and gale force winds.
Saturday morning, southern Clarence Strait will reach gale force
winds of 35 kts with winds gusts of 40 to 45 kts possible. Expect
strong breezes to extend as far north as Frederick Sound, mainly
from an SE to ESE direction. Not looking to have these stronger
winds travel up into northern Chatham Strait or Stephens Passage,
although there is approximately a 30% chance of exceeding fresh
breeze in Peril Strait.

In the northern half of the panhandle, expect winds to flip out of
the north as the stronger front moves up from the south. Moderate
breezes in Lynn Canal from the northerly winds are expected, with
fresh breezes near Point Couverden out of the NE, due to a tip
jet.

A marine weather statement has been issued focused on the stronger
winds and waves on Saturday.

&&

.HYDROLOGY...As far as rainfall amounts, both high res models and
the EC and GFS ensembles are showing between 0.5 and 1.0 inches
every 12 hours for the southern panhandle beginning tonight and
lasting through tomorrow night. Less QPF is expected for Sunday
and Monday with much lighter rain rates before the next system
moves in. Areas on the windward side of mountains could get a
little more. A stronger system will be moving in Monday night into
Tuesday with a wet moisture plume and a weak to moderate
atmospheric river for the southern half of the panhandle. So far
the EC is showing the atmospheric river to be moving more directly
into the panhandle Tuesday, while the GFS is having it move more
to the southeast and with a bit more spread in the strength of the
AR event. The EC showing this to be a moderate AR for the southern
panhandle is also shown in the EFI QPF table, with a shift of
tails of 2 and confidence above the 90th percentile for a
significant portion of the panhandle. For now it`s something
we`re watching as we get closer and have more agreement on the IVT
values and timing/placement of the AR. We are not seeing any
flooding concerns for now for this event.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning for PKZ036.
Small Craft Advisory for PKZ033-035-641>644-661>664-671-672.

&&

$$

SHORT TERM...Contino
LONG TERM....GJS
AVIATION...Bezenek
MARINE...NC
HYDROLOGY...Contino

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