Gale Warning 382, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
528 AM AKDT Sat Apr 13 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
This morning through Monday night)...

A vertically stacked upper-level low currently located over the
Kenai Peninsula is producing showery conditions along the gulf
coast and northwards into the central Chugach Mountains and Copper
River Basin. This trend should continue through the afternoon
hours as the low continues to move southeastward towards Prince
William Sound. Precipitation currently falling is mostly in the
form of snow, however heating later today could result in a
rain/snow mix or fully transition to rain as temperatures climb
into the mid-to-upper 30s. Anchorage and the Kenai Peninsula will
have a chance for light snow showers this morning as sufficient
moisture from the low has been pulled westward over the Chugach
Mountains.

The upper-level low will begin to move south into the gulf as a
building ridge enters southwest Alaska Saturday evening.
Widespread precipitation will end as drier air aloft will move in
with the ridge of high pressure. As the ridge moves eastward, a
north to south pressure gradient will begin to form along the
gulf coast late Saturday. This will result in offshore gap winds
taking place through Sunday afternoon.

Southerly flow near the surface late Monday night will provide
the next chance for precipitation as upslope flow will be
favorable along the coastal Kenai and Chugach Mountains, as well
as the western Alaska Range.

-BS

&&

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

A ridge of high pressure has moved over the western Aleutians and
Bering Sea northward into western Alaska this morning. This has
resulted in fairly benign weather conditions for much of the region
with the exception of ongoing gap flow winds and some lingering snow
showers across the eastern Aleutians and AKPen. The gap winds will
gradually decrease through the day today as the trough currently
extending from the Kenai Peninsula southward along the eastern side
of the AKPen continues to move eastward into the Gulf, and the ridge
axis shifts east. Any lingering showers over the AKPen will also
shift eastwards. Given generally clear skies over Southwest Alaska
overnight, temperatures will start in the single digits to lower
teens, but should easily bump up into the upper 20s to lower 30s as
cool northerly flow backs to more westerly. Cloud cover will begin
to increase later this morning through early afternoon as a weak
disturbance moves into northwest Alaska by this evening. Any
precipitation from this system looks to be light and looks to remain
confined to the Kuskokwim and Kilbuck Mountains. Sunday will see
ridging build back over the central Bering and Southwest Alaska.

For the latter half of the weekend...attention turns to a system
approaching the western and central Aleutians from the North
Pacific. The GFS and NAM continue to lift this system across the
Bering and into the Bering Strait through early next week.
Meanwhile, the Canadian and ECMWF are sticking with the more
southern track across the central Aleutians before quickly
weakening the low as it moves into the western Bering Monday
night. Given the very different upper low tracks, have continued
to trend more towards the GFS/NAM solution which would result in
gale to storm- force winds working across the central Aleutians
and into the Bering. Precipitation will generally be all rain for
the Aleutians with the Pribilof Islands starting out as all snow
before changing over to a mix as warmer air begins to work in.
Modest confidence remains that there may be a period of blowing
snow across portions of the Kuskokwim Delta Coast, Nunivak Island,
and the Western Capes before temperatures warm behind the frontal
boundary.

- PP

&&

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

A pattern shift is on tap in the long term forecast period. Expect
the ridge to break down. A series of North Pacific Lows will push
into the Gulf and moisture from the Central Pacific Basin will
move towards Southcentral. However, model agreement regarding the
timing of these lows is still not exactly in sync but they are
locking on to the concept of a wetter and windier pattern for
Kodiak, the Barren Islands and other parts of Southcentral. Given
its origin and potential orientation of these moisture fetches,
this may also lead to another precipitation event for the Prince
William Sound communities. For Southwest Alaska, the temperatures
will be below seasonal norms this forecast period but beyond that
the vagaries of the models leave much to be desired. Out west
over the Bering and NW Pacific, the models are all over the place.
The run-to-run continuity for the NW Pacific and Bering has been
poor for the medium range for multiple runs of the global models.

&&

.AVIATION...

PANC...VFR conditions and light winds will generally persist. Some
areas of snow showers could still bring ceilings/visibility down
to MFVR range for the first few hours this morning. However, weak
and drying northerly winds should help clear this activity out by
midday today.

&&