Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 260049
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 PM AKDT Mon Mar 25 2024

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

Numerous to widespread rain showers continue along the north Gulf
coast this afternoon as a shortwave trough extending from
Southwest Alaska out over the western Gulf lifts northward into
Southcentral. The robust southeasterly flow on the north side of
the trough axis continues to keep much of inland Southcentral dry
as downslope flow suppresses the development of precipitation.
However, various weak shortwaves embedded in the flow have been
able to overcome the subsidence, leading to brief periods of
scattered rain showers over the western Kenai Peninsula,
Anchorage, and the southern Susitna Valley. This general pattern
will continue, with the same areas having a chance to see light
rain showers this evening. The core of the main shortwave lifts
across the Cook Inlet region tonight, which should lead to a
period of more numerous rain showers overnight, with the
Matanuska Valley and the northern Susitna Valley joining in on the
action as well. While cooler air begins to move in aloft
overnight, temperatures near the surface look to remain warm, with
forecast lows similar to last night, remaining above freezing at
most locations and with precipitation type remaining rain. Inland
Southcentral sees decreasing precipitation chances by Tuesday
morning as the trough axis exits northward and no significant
source of forcing appears present to overcome the continued
(albeit weak) downsloping.

Focus then shifts to a shortwave trough driving up out of the
North Pacific and over the Alaska Peninsula for Tuesday, as this
feature brings the next chance for precipitation for inland
locations. However, forecast uncertainty increases as model
guidance diverges on its evolution. Guidance falls generally into
two camps, one where the shortwave lifts into Southwest Alaska
and elongates before drifting slowly eastward, and the other where
the shortwave`s energy focuses slightly further eastward and lifts
more quickly across Southcentral. The more westward/slower track
leads to a band of precipitation setting up over the southwestern
Kenai Peninsula (primarily affecting Homer and Seldovia) on
Tuesday and lingering there potentially into Wednesday - solutions
favored by the GFS and GDPS (Canadian) today. Alternatively, the
NAM and the bulk of the high resolution guidance favor the more
eastern focus, where a weak front pushes up Cook Inlet and brings
precipitation into Anchorage and the Mat-Su through Wednesday
morning. Notably, the further west solutions also bring
precipitation to Anchorage and portions of the Mat-Su Valleys
thanks to a wave lifting northwestward across the Copper River
Basin. As a result, generally expect another round of light precip
sometime in the Tuesday through Wednesday timeframe for much of
the area around Cook Inlet. As for precipitation type, colder air
moves in Tuesday night, and while precipitation looks to begin as
rain near Homer during the day, it quickly transitions to snow
Tuesday night regardless of solution. Snow accumulations will be
light, generally up to an inch, with maybe two inches in locations
that see more prolonged snowfall.

By Wednesday, cold air associated with a low over the Bering
shifts east and filters across the Alaska/Aleutian Range, leading
to increasing westerly gap winds (though likely below gale force)
and generally light northerly gap winds along the north Gulf
coast.

CQ

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, the BERING SEA and the
ALEUTIANS (Days 1 through 3: Tonight through Thursday)...

GOES satellite imagery shows a cold upper-level low centered near
Saint Matthew Island in the Bering Sea. The attendant cold front is
gradually pushing onshore across southwest Alaska, with
precipitation focused near the front/trough. Cooling behind the
front has resulted in rain transitioning to snow across the Lower
Kuskokwim Valley. The same is expected to occur across the Bristol
Bay area later this evening and overnight. Approximately 1 to 3
inches of new snowfall is expected from Togiak northward through
about Bethel. Elsewhere, less than an inch is expected.

Meanwhile, behind the low, cold northerly flow across the eastern
Bering will maintain snow showers across the open water. Occasional
snow showers will move through the Pribilof Islands from this
evening through mid-day Wednesday. Snowfall generally in the range
of 1 to 4 inches is expected across the islands over the next couple
days.

By late Wednesday, attention turns towards a low that`s expected to
deepen across the North Pacific as it moves towards the western and
central Aleutians. Models have come into a bit better agreement with
placement and timing of this low, with trends showing a low a little
bit slower and stronger than previous model runs. The associated
front should push through the central Aleutians Wednesday
evening/overnight as the surface low is projected to move through
the Rat Islands. A brief period of heavy snow and strong wind is
possible for Adak before temperatures quickly warm to above
freezing. This low is expected to bring widespread storm-force (>48
kts) winds and a smaller area of hurricane force (>64 Kts) gusts to
the Aleutians on the south/east side of the low, affecting primarily
Adak and Atka. Should trends continue and confidence increasing, a
high wind warning may be needed for these areas.

The low will progress towards the Pribs on Thursday with the
associated front and strong push of southerly winds into southwest
Alaska late Thursday into Friday. Some areas across southern Bristol
Bay into the AK Peninsula may see a transition to rain, but
elsewhere across southwest Alaska should maintain snow given
residual colder air in place. Snow combined with strong wind may
result in blizzard conditions up towards the Kuskokwim coast. This
situation will continue to be monitored.

-Brown

&&

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

The upper level closed low center drifts Northward towards the
Arctic through the period. Owing to some rather energetic overall
windflow, mixing a shot of polar air with more continuous support
from the North Pacific, the elongated trough moves into the
Western Mainland. Another round of Arctic air enters the picture
towards the end of the forecast to assist in further Eastward
movement. Models remain broadly clustered with decent ensemble
support through the weekend.

The weather pattern is shaping up to become a large area, multi-
day precipitation event. A well developed surface low and front
swings from the Central Aleutians to the West Coast before
circling back to the Central Bering through Monday. Widespread
gusty winds wrap the low with areas of gale force gusts move from
the Central Aleutians Friday and Saturday to the Alaska Peninsula
and Southwest Alaska through Monday. There is potential for some
beach erosion and coastal flooding across Northern Bristol Bay,
the Kuskokwim and Yukon Deltas, and the South side of Nunivak
Island. Locally heavy rainfall spreads across the Aleutians and
AKPEN through Monday, with areas of heavy snow pushing into the
Kuskokwim Valley and along the Southern Alaska Range for Saturday.
Another front approaches the Western Aleutians late Sunday into
Monday with more rainfall and gusty winds.

The sustained Southwesterly flow spreads locally heavy rainfall
to the Southcentral Coasts from Kodiak Island and from the bottom
of the Kenai Peninsula to the Canadian Border. Rain mixed with
snow pushes further inland. Gusty winds around Kodiak Island
Friday diminish briefly early Saturday, but a second wave late
Saturday through Sunday follows before dissipating.

Kutz

&&

.AVIATION...

PANC...VFR conditions and light winds are expected to persist
through the TAF period. Occasional sprinkles or very light rain
showers are possible through Tuesday as a series of fronts
continue to lift through the Gulf and linger across the northern
Gulf Coast. Generally, ceilings will likely remain above 5,000 ft,
but could fall to between 3,500 ft and 5,000 ft briefly in rain
showers.

&&

$$


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