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FXAK68 PAFC 210050
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 PM AKDT Mon May 20 2024

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

An upper level low in the eastern Gulf of Alaska continues to
weaken as it exits the region this evening. Some precipitation is
possible in the eastern edge of the forecast area as the system
meanders towards the Alaska Panhandle. Calmer conditions will
persist across Southcentral through most of the overnight hours
tonight before the next upper level low enters the area.

The front ahead of the next upper low, currently located in the
eastern Bering, will start impacting Kodiak Island this evening
before the rest of the extended front crosses over the Alaska
Range later tonight. Widespread rain and snow will be seen over
much of the area, with some locations receiving heavier rates of
precipitation at times. Southwesterly flow aloft will allow the
Anchorage Bowl to get some precipitation Tuesday afternoon as the
front passes. Additionally, a building pressure gradient across
much of the Chugach and Kenai Mountains will produce southerly
gap winds near the Kamishak Gap, Turnagain and Knik Arms, and the
Copper River Basin starting tomorrow morning and extending into
Wednesday.

As the upper low continues to move eastward into the mainland, a
secondary cold front will start extending out ahead of the low
Wednesday into Thursday. This will cause temperatures to drop
below normal for most locations, increasing the potential for snow
to occur at some lower elevations as snow levels decrease. In
recent model guidance, the upper low is trying to form a
deformation band over the Anchorage Bowl and Mat-Su Wednesday
night which would produce increased precipitation totals for that
part of the forecast area. A chance for rain and snow showers
will persist through Thursday afternoon before the low starts to
weaken and move eastward towards Canada.

-BS

&&


.SHORT TERM FORECAST FOR SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3)...


A low pressure system will continue to progress east-
northeastward through tomorrow evening bringing a mix of rain and
snow showers for Southwest Alaska, the Aleutians and the Alaska
Peninsula. Its front that brought precipitation this morning and
early afternoon will continue to move northward through the
evening resulting in most of the precipitation in Alaska Peninsula
ending later this afternoon. Overnight, a second wave of
precipitation will move onshore bringing widespread rain/snow
showers from Togiak-Dillingham-New Stuyahok northward to
Mekoryuk-Lower Kalskag-Crooked Creek area. Shortly before
daybreak break tomorrow, the heaviest precipitation is expected in
Aniak-Crooked Creek south to Dillingham and eastward to King
Salmon-Iliamna. This area of heavy precipitation will move slowly
eastward through tomorrow afternoon and most of it will fall as a
mix of rain/snow with cooler air filtering into the region. QPF
amounts range from 0.25" to 0.75" across all of Southwest Alaska
from today into tomorrow afternoon. Widespread low clouds and
areas of fog are possible overnight and into tomorrow, too.

Westerly to southwesterly wind gusts will be strong in the
Aleutians tomorrow from dawn through the late afternoon hours
ranging from 30 to 40 mph. Elsewhere, localized southerly/southeasterly
wind gusts through the Kamishak Bay will be strong tomorrow
ranging from 30 to 40 mph for most of the morning hours; subsiding
in the afternoon.

A weak ridge moves quickly through the Aleutians tomorrow
morning, the Alaska Peninsula during the late morning morning and
onshore in Southwest Alaska beginning early tomorrow afternoon
bringing a short reprieve to the precipitation. A weak wave brings
some precipitation to the Goodnews Bay/Togiak area tomorrow
evening. A stronger low pressure moves through the Bering Sea
Thursday evening through Friday bringing a return to moderate
precipitation and gusty to gale force winds later this week.


DJ

&&

.LONG TERM FORECAST (Days 4 through 7)...

Friday, an upper-level low over the eastern Bering drops across
Southwest Alaska and into the Gulf by Saturday afternoon. A
trough sets up over the western coastline bringing possibly mixed
rain and snow for the Western coastline and all rain elsewhere,
primarily to Kodiak and the eastern Kenai. A high pressure ridge
forms across the Bering before the next upper-level low
consolidates and moves eastward from the vicinity of Attu Island
on Monday.


&&
.AVIATION...

PANC...VFR conditions will persist through the TAF period. A mild
Turnagain Arm wind will develop and impact the terminal late this
evening/early tonight, continuing overnight. The Turnagain Arm
jet will strengthen further late Tuesday morning/early afternoon,
with the strongest winds expected to remain away from the
terminal. Confidence is relatively low as to how persistent the
winds will be over the terminal, but the winds are likely to be
swinging in and out of the terminal for much of the day Tuesday.
Ceilings will drop to 3500 to 5000 ft and may briefly reach MVFR
criteria Tuesday afternoon.

-ME

&&


$$