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FXAK68 PAFC 120045
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
445 PM AKDT Thu Apr 11 2024

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

Overall, the forecast remains largely on track. Wet and windy
weather persists for Southcentral Alaska through tomorrow
morning/afternoon. Then, sunnier weather is on tap for the
weekend as a colder and drier air mass moves in. The primary
hazard we`re monitoring is the Winter Weather Advisory for Broad
Pass, which remains in effect through late tomorrow morning.

Diving into the details...a front extending from Northwest Alaska
into the Gulf will gradually move east across Southcentral
through tomorrow morning. A strong south-to-north pressure
gradient is helping to enhance the gusty southerly to southeasterly
winds associated with the front. Winds have been a bit of an
over-performer today, gusting as high as 45 to 55 mph in West
Anchorage, Palmer, and Gulkana. Expect these gusty winds to peak
tonight, then gradually diminish through tomorrow morning.

Precipitation generally looks on track with this front, though
there are a few areas that may bear closer watching through
tonight. For Anchorage, stronger downslope drying has kept
snowfall limited to no more than a few flurries earlier this
morning and afternoon. Similarly, we`ve cut back on precipitation
chances for Matanuska Valley this evening due to downslope drying.
Further south, locations along Prince William Sound/Eastern Kenai
Peninsula could see minor visibility reductions as moderate to
heavy snow moves in later this afternoon/evening. There remains
some question of whether rain may mix in with snow for these
coastal locations.

By late tonight, the front will finally shift east past the Kenai
Peninsula and reach Prince William Sound as it begins to weaken,
with a weak triple point low likely forming somewhere near Prince
William Sound as well. This will allow strong and gusty gap winds
to weaken and turn more southwesterly by tomorrow morning. Farther
north, a shortwave trough will quickly move east into the Susitna
Valley and Talkeetna Mountains tomorrow morning at about the same
time southeasterly winds at the surface begin to wane. This could
set up a quick burst of snow moving across Anchorage and Matanuska
Valley before cooler and drier air begins to move in from the
west behind the trough passage later in the day.

Looking briefly out towards the weekend, the pattern is set to
become much drier and quieter as a broader upper trough axis
pushes southeast and offshore on Saturday, with dry northwest
flow and upper level ridging building back in behind it through
Saturday night. Seasonable temperatures in the 30s and 40s with
some sun will return for much of the area by Saturday afternoon
and evening. With little to no precipitation expected, the primary
challenge with the forecast this weekend will likely be honing in
on the strength of gap winds.

-AS/KC

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, BERING SEA, AND ALEUTIAN
ISLANDS (Days 1 through 3)...

Interestingly, on satellite imagery (CIMSS Mimic PW) there is a
discernible moisture fetch that extends from the Philippines to
the AKPEN and actually north of the Brooks Range. This is an
impressive moisture fetch with portions of this plume more than
350 percent above normal (total precipitable water). These
anomalies extend inland to and north of Lime Village. There is a
surface low near Nunivak and the associated cold front will push
over southwest Alaska. A strong pressure gradient remains between
the low and a ridge south of the Alaska Peninsula. Expect showery
and gusty weather for SW AK into Friday but Saturday and Sunday
will be mild and relatively dry. There is a dome of high pressure
over the Central Aleutians/Bering that will slowly move eastward.
By Saturday night there will be another low closing in on the
Western Aleutians. The models diverge with the track of this
second low on Sunday.

&&


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

A pattern shift is the looming potential in the long-term period,
with the degradation of the ridge built over Southern Alaska
beginning Monday. This is furthered by multiple North Pacific Lows
pushing towards our area, replacing the calm pattern with an
active wet and windy one. However, model agreement regarding the
pacing of this transition is poor so timing the return of
stronger winds and precipitation is difficult until the guidance
comes to a better agreement. It is likely however that by
Tuesday/Wednesday, gusty southeasterly winds would return to
Kodiak Island and through the Barren Islands. This would come in
the form of a frontal boundary on the northern leading side of a
north pacific low moving in. Given its origin and potential
orientation, this may also lead to another precipitation event for
the Prince William Sound communities. Expectations further west
in the Bering suffer from even worse model agreement, with
drastically different solutions being advertised by the models
even as soon as Wednesday morning. Agreement does not improve
throughout the region by mid-to-late next week.

-CL

&&

.AVIATION...

PANC...VFR conditions will persist through the evening hours as
downslope drying from strong southeasterly winds keeps precipitation
aloft from reaching the ground. Winds will veer to the S to SW
and begin to weaken overnight. This This should be just enough to
allow a brief period of snow with a lowering of ceiling/vis. With
some gusty winds still in place at the surface, it`s hard to say
how low conditions will get, but the worst conditions will only be
for an hour or two before VFR conditions settle back in. Winds
will gradually diminish through the morning hours on Friday.

&&


$$