Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 301255
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
455 AM AKDT Mon Mar 30 2020

.ANALYSIS AND UPPER LEVELS...
A 1040 mb strong surface high pressure system is present across
much of mainland Alaska and the Northwest Territories of Canada
underneath a large upper level ridge. As a result, clear skies
were observed across much of the mainland. A strong surface
pressure gradient remained present this morning across
Southcentral due to a 1040 mb high over Canada and 1007 mb low
over the southern Gulf. This kept winds gusting upwards of 55-60
mph at Thompson Pass, 30-40 mph in Valdez and gusting 50-55 mph in
the Matanuska Valley. Temperatures in the teens were observed
across much of Southwest Alaska with light winds and clear sky.
High wind warnings remain in effect for Thompson Pass and the
Matanuska Valley.

A north-south oriented front was observed across the central
Aleutians and Bering bringing rain to the central Aleutians as
well as gusty winds in the small crafts to gale force range. Light
winds were out of the south and east-southeast ahead of the front
along the eastern Aleutians from Dutch Harbor to Cold Bay.

&&

.MODEL DISCUSSION...
Models remain in good agreement with the major features through
Wednesday. Differences continue to remain for Southwest Alaska on
the timing of the event as well as the strength of this low. The
exact track will also determine just how much warm air comes in
for the Alaska Peninsula areas which will affect the QPF and
snowfall amounts.

&&

.AVIATION...
PANC...Gap winds exiting the Matanuska River Valley will bend
southward down Knik Arm and near the terminal. While there may
be an occasional break in the wind, gusty northerlies will
prevail through Monday morning. Winds will then shift west of
the terminal and weaken. VFR conditions (clear skies) will
prevail through the period.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

Offshore flow and gap winds will continue across Southcentral
through the day on Monday. A strong upper level disturbance is
expected to move across the Susitna Valley in the morning, then
linger over the eastern Chugach this afternoon. This should cause
winds to remain strong through the Matanuska Valley this morning,
but then taper off before the winds peak in the Valdez area. Some
blowing snow may remain in the Matanuska Valley, but most of the
snow will be crusted over so visibility won`t be majorly impacted.
By the early evening the upper level disturbance will move off to
the south and winds will quickly diminish. With high pressure in
place for Southcentral, expect Tuesday to dawn clear and cold,
with temperatures in the single digits around Cook Inlet and 0 to
10 below in the Copper River Basin. During the day, abundant
sunshine should warm the temperatures to near normal.&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3/Monday
through Wednesday...

Clear conditions will continue to be seen across Southwest Alaska
early today before the clouds begin to make their return to
coastal locations this afternoon. The cloudy weather will continue
to move in this afternoon as a weakening front over the eastern
Bering progresses eastward. Most of Southwest Alaska will remain
dry, except for the Kuskokwim Delta, which will see a brief period
of light accumulating snowfall moving in this afternoon through
the overnight hours. The increase in cloud cover moving back into
the region will help to warm temperatures for the next few days.

Tuesday morning will start off with quiet conditions as the first
front dissipates before the next round of snowfall across the
Alaska Peninsula and Bristol Bay late Tuesday as a North Pacific
low lifts northward. There is still some model uncertainty in
timing of when this system will move into the region and how far
inland it spreads for Tuesday evening into Wednesday. However, it
does look like there will be significant snowfall accumulation of
at least advisory criteria with this system. Stay tuned to future
forecasts to get an update on how models are handing the snowfall.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2/Monday
and Tuesday)...

A front stretched over the central Bering and Aleutians will bring
a quick shot of snow to the Pribilofs this morning. As it
continues eastward into the eastern Bering, the front quickly
weakens through the overnight hours, with high pressure building
in behind this system through tonight.

The next significant system associated with a North Pacific low
will begin to move over the eastern Aleutians and Alaska Peninsula
early Tuesday. Precipitation initially will start off as snow, but
will transition over to rain by Tuesday afternoon for most areas
as warmer temperatures begin to move in. Strong winds will
accompany this system, but models are still uncertain as to
whether a pocket of gale force winds will develop south of the
Alaska Peninsula for Tuesday evening.

The next strong system will approach the western Bering on
Wednesday.

&&

.MARINE (Days 3 through 5/Wednesday through Friday)...

Bering Sea and Aleutians...
On Wednesday, there is better model agreement today with the
front entering the northwestern Bering. Winds are forecasted below
gale force at this time, but there will likely be gale force
winds and widespread precipitation accompanying this system that
is showing a stronger signal than yesterday`s model runs. Thus,
confidence is improving in the track and intensity of this low.
Impacts of this in the eastern Bering are minimal as the front is
expected to dissipate before reaching that area through Thursday.

Gulf of Alaska...
There is a chance of small craft southeasterly winds across the
western Gulf on Wednesday associated with a low over Bristol Bay.
Confidence in these small craft winds is low as there are
significant differences in solutions for the low track and
intensity. For Thursday there is low confidence in the wind
forecast, though the weather pattern is expected to remain benign.

&&

.LONG TERM FORECAST (Days 3 through 7/Wednesday through
Sunday)...

Guidance is consistent with an upper level ridge extending across
the Alaskan mainland on Wednesday as an upper trough is present
over the Bering/Aleutians. Due to this, temperatures will be
warmer with a benign weather pattern over the Alaskan mainland and
cooler with a more active weather pattern over the Bering/Aleutians.
Uncertainty increases into Thursday as guidance shows a higher
degree of variation in solutions with upper level synoptic features
which will affect the placement and intensity of surface synoptic
features. The only area of consistency is the upper level ridging
will continue over the eastern Alaskan mainland near the AlCan
border and thus, expect warm temperatures and quiet weather for
that region. Very low forecast confidence exists overall Friday
through Sunday as major differences in upper level synoptic
features exist between guidance which is causing significant
differences in the placement of surface features causing a high
degree of uncertainty in the forecast.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning 111 and 131.
MARINE...Gale warning 127
Heavy Freezing Spray 140 160 180.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...MV
SOUTHCENTRAL ALASKA...LF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AH
MARINE/LONG TERM...AH/ED


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