167
FXAK68 PAFC 010036
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
436 PM AKDT Wed Apr 30 2025

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

A low pressure system once over the northwestern Gulf of Alaska
has shifted north up the Cook Inlet inland. An occluded front
stretched across the northern Gulf Coast including Prince William
Sound communities will continue to see persistent rainfall this
evening. As the low pressure center shifts near Anchorage late
this afternoon, gusty winds will be drawn from the east out of
Turnagain Arm and potentially curl up into portions of the
Anchorage area. These gusty winds are expected to be short-lived
as the low center weakens tonight and shifts further north, with
winds winds weakening significantly and shifting northeasterly
after midnight. A similar gusty pattern is expected for the Palmer
area, with gusty winds coming out of the Knik River valley,
potentially lofting glacial silt and blowing dust this evening,
diminishing by midnight tonight. Gusty winds out of the Southeast
are also expected through the Copper River Valley including
Gulkana and Glennallen early tonight, diminishing similarly by
midnight tonight. Finally, strong easterly winds driven by a
barrier jet along the northern Gulf coast will diminish this
evening.

Starting tomorrow, a prolonged period of mild, unsettled weather
will continue, with calmer winds across the region, but prolonged
rainfall expected along the coast, and light showers possible for
inland locations through the remainder of the workweek. Areas at
elevation such as Thompson Pass may see periods of wet snowfall
along the roadway, however it is not expected to accumulate,
instead melt rapidly. Thursday evening, a low pressure system from
the northern Pacific is expected to swing up into the northern
Gulf, reinforcing the pattern in place. Anchorage, Western Kenai,
and Mat-Su valleys may see periods of light showers through the
remainder of the week, however downsloping off the mountains is
expected to mute much of the impacts observed.

-CL

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (through Saturday afternoon)...

A cold upper level system lingers over the southwest Mainland. The
convective nature of the rain is evident from the King Salmon
RADAR this afternoon, but no signs of lightning detected yet.
Model guidance continues to show weak instability from coastal
Bristol Bay northwestward into the Kuskokwim Delta through this
evening, and isolated lightning strike can not be ruled out. Small
hail and brief periods of heavy rain will be the main impacts.

The scenario for Thursday is nearly identical to today, however
the system overhead continues to weaken. Instability will be
mostly dependent on where gaps in the low level cloud cover
develop and allow for surface heating. In general, across the
southwest, expect partly to mostly cloudy conditions with
scattered rain showers and isolated thunderstorms. High
temperatures in the upper 40s to low 50s. On Friday a disturbance
and weak front from the Gulf of Alaska will bring rain to the
slopes of the Alaska/Aleutian range. The next system will be
transiting south of the Alaska Peninsula and largely not affecting
the mainland.

MTL

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (through Saturday
afternoon)...

Fairly quiet conditions across much of the Bering Sea as weak cold
advection produces snow showers over much of the area. Across much
of the Chain, temperatures are warm enough for rain showers. The
next system will again move west to east along or just south of
the Aleutians Thursday through Saturday. There will be some gale
force winds, mainly south of the central Aleutians. Adak and Atka
will likely see rain turning to snow as the system transits to the
south, becoming snow showers when the system passes on Saturday.


MTL

&&


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

A rather active weather pattern sets up across the Southern
portions of Alaska through the forecast period. On the upper level
map, a closed low South of the Eastern Aleutians and Southern
Alaska Peninsula intensifies briefly as it moves into the Gulf of
Alaska late Monday into Tuesday. This low will then weaken as it
drifts out of the Gulf for Wednesday. A moderate ridge moving
across the Aleutians and Bering flattens out near the AKPEN by
Wednesday. Another closed low slips out of the Russian Far East
for Wednesday. A loose cluster of ECMWF and GFS deterministic
models work the major features through Tuesday before yielding to
ECMWF / GFS means for Wednesday. Considerable uncertainty rests in
the minor details throughout the forecast.

A well developed and intensifying surface low South of the AKPEN
gains its greatest strength passing Kodiak Island Tuesday. With
its front extending across the Gulf of Alaska, areas of moderate
rain spread across from the AKPEN and Kodiak Island to the
Southcentral coastal zones through Tuesday, diminishing Wednesday.
Some moderate snow is expected over the higher elevations of the
AKPEN and Southwest Alaska into Bristol Bay and Eastern Bering.
Heavy rain moves into Kodiak Island Sunday. A strong North Pacific
low and its front spreads moderate rain across the Western
Aleutians and Bering Tuesday, moving into the Central Aleutians
and Bering by midweek.

- Kutz

&&

.AVIATION...

PANC...VFR conditions are expected to persist. Strong
southeasterly winds are expected to develop by late afternoon
behind a low that will move across the Kenai Peninsula and into
the western Susitna Valley this afternoon and evening. With this
type of system, then onset of the southeasterly winds will
probably be fast and strong with gusts to 35 kt or higher possible for
an hour or two after the southeast winds start. After that they
should be more typical southeast winds with gusts closer to 25 kt.
These winds should then rapidly decrease and turn back to the
north around, or shortly after midnight tonight.

&&


$$

146
FXAK67 PAJK 010654 AAA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
1054 PM AKDT Wed Apr 30 2025


SHORT TERM...Wet and windy short term with a plume of moisture currently
directed at the Yakutat area will be shifting eastward over the next
12 hours. Expect a strengthening of both winds and precipitation as
it moves eastward, as a shortwave trough moves up along the plume of
moisture. Gusts exceeding 30 mph for most land locations will begin
tomorrow morning, coinciding with periods of moderate to heavy rain.
For more information regarding hydrology, see hydrology section. The
bulk of the front will move through the panhandle tomorrow night,
but exact timing of frontal passage is lower confidence. Model
guidance are fluxing between 4 PM and 10 PM for when the front will
finally push through the panhandle and shift winds. Main determining
factor will be how fast the front will be able to break down the
ridging in British Columbia. Current solution represents the high
pressure breaking down slower, meaning heavier rain and winds
sticking around for longer.

LONG TERM.../ Friday through Wednesday / A quick moving ridge is
is pushed east over the Eastern Gulf and Panhandle Friday and into
Saturday. Moving this along is the next incoming frontal band
associated with upper trough and moving in from the north pacific
and combining with a trough dropping SE from Eastern Russia over
the Bering. The upper level feature pulls up towards the Alaska
Peninsula, and the frontal sweeps across the gulf Sunday and into
the panhandle by Monday, bringing with it the organized band of
moisture and wind to start the week.

Upper level low will persist in the central gulf into the middle
of the week. This will lead to continued onshore flow and
shower activity for the panhandle.

AVIATION...Gale force front will continue pushing through the
panhandle into Thursday, bringing moderate to locally heavy
precipitation and gusty winds. CIGs along the NE coast will be AoB
1500ft with intermittent visibilities as low as 2SM in heavier
showers from the primary moisture plume. For the rest of the
panhandle, conditions start out VFR and will deteriorate later
tonight as the main precipitation band and elevated winds push
inland. By Thursday morning expect elevated winds, lowered VIS due
to widespread precipitation and CIGs will begin dropping,
ultimately reaching AOB 1200 feet for some locations through
Thursday. Main concern will be widespread LLWS for coastal and
southern TAF sites. Southeasterly LLWS around 1000 ft to 2000 ft
will peak for Yakutat this evening, while southern TAF sites of
Sitka, Klawock, and Ketchikan will see southeasterly LLWS build
through the evening hours and last into Thursday morning before
beginning to diminish Thursday afternoon.


MARINE...Not much change to the overall marine forecast, expect for
Thursday night.

Outside: As advertised, latest ASCAT pass shows strong gales
right up along the coastline near Cape Suckling, around 45 knots.
While gusts are not calculated using this satellite product, it is
not a stretch to say gusts in that area are exceeding 50 knots,
prompting the earlier marine weather statement. No change for the
timing of gales along the gulf coast, nor major changes in the
15-20 ft seas.

Inside: For the inner channels, made some edits to Lynn Canal to keep winds
lighter for longer. Expecting a largely parallel gradient with
little directing flow aloft until at least Friday morning as an
upper level trough moves into Canada with rapid pressure rises
behind it beginning Thursday night. As the front moves through
tomorrow afternoon, with lower confidence on exact timing of the
frontal passage, wind directions will shift from southeast briefly
to south to southwest. Then, as pressures rise, fresh southerly
breezes to 20 knots will move up through Chatham Strait and Lynn
Canal.

HYDROLOGY...A wet 48 hours is expected for the entire panhandle as a
plume of moisture currently directed at Yakutat area will slight to
the east. MIRS rain rate product, displayed over the NE gulf coast,
show rain rates over Yakutat of around 0.25 in/hr. Upstream, an
embedded trough moving up along the plume will bring enhanced rain
rates to the rest of the panhandle beginning overnight and extending
through the morning hours Thursday. CIMSS MIMIC PW relative to
normal show an increasing plume currently around 250% of normal
racing up to the southern panhandle. What this will translate into
is heavy rain rates from Juneau to Ketchikan overnight tonight
through the morning hours Thursday, with rates possibly exceeding
0.2 inch per hour. Only expecting these rates to stick around for
around 6 hours as the front passes, but longer duration onshore flow
will ramp up totals more. Currently, Glacier Bay/Icy Strait area,
Juneau, and NE gulf coast including Yakutat appears to be the big
winners here in terms of totals. Over the next 24 hours, expecting
around 1.5 - 2.5 inches of rain, which are daily record amounts for
many places. While in fall time, this amount may not seem like much,
during late April, it is unusual to see this amount of rain
accumulation. Regardless, expecting soils to absorb most of the
rainfall associated with this system, meaning that river rises will
be dampened significantly. Therefore, rivers will rise, but are
expected to remain within bankfull conditions. No flooding is
expected.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 7 AM AKDT Thursday for AKZ323.
MARINE...Gale Warning for PKZ036-641-642-652-661>664-671-672.
Small Craft Advisory for PKZ021-022-031>035-053-643-644-651.

&&

$$

SHORT TERM...99
LONG TERM....99

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