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FXAK68 PAFC 181339
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
539 AM AKDT Fri Oct 18 2024

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

Strong and gusty winds with seasonably cool temperatures continue
to dominate the overall pattern as we head into the upcoming
weekend. Gusts as high as 40 to 50 mph have materialized as
anticipated from yesterday afternoon into this morning across
parts of the Matanuska Valley, Thompson Pass and down into Valdez
at times, with slightly weaker winds still impacting Whittier,
Seward, and west Anchorage. These strong winds are owing to the
tight pressure gradient and strong northerly flow in place between
a low and upper trough digging into the Gulf and a strong ridge
in place over the western Mainland and Bering Sea. This same
synoptic pattern with gusty northerly winds at times and cool
temperatures really will not change too much for the next 24
hours, with another reinforcing shortwave set to drop south across
the western half of the region and down into the Gulf by tonight.

By Saturday, gap winds will begin to relax somewhat as the ridge
out west expands into Southcentral and as the low in the Gulf
weakens and drifts towards the Alaska Panhandle. With the
exception of northwesterly winds near the Barren Islands and
Shelikof Strait, gap winds will finally come down in earnest on
Sunday as the entire upper ridge moves directly overhead and as
upper level flow shifts from southerly to westerly. Cloud cover
will begin to increase as well through Sunday night ahead of a
strong frontal system moving over the Bering and Southwest, which
will become the next system of interest for Southcentral by later
next week.

-AS

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Today through Sunday)...

High pressure has overspread the Bering, resulting in plenty of
low stratus and fog region-wide. On the downstream side of the
ridge, northerly flow through the Eastern Aleutians and Alaska
Peninsula is resulting in some gusts up to around 20 knots. Winds
should gradually diminish through the remainder of the morning
hours as a low over the eastern Gulf weakens and moves inland of
Southeast Alaska, easing the pressure gradient across the Eastern
Aleutians and AKPEN. Across Southwest Alaska, satellite imagery
reveals largely clear skies with the exception of patchy fog in
low lying areas, as well as an area of low-level confluence over
the YK Delta. An axis of low stratus and fog is noted on satellite
stretching from the Seward Peninsula down into Kipnuk. Some of
this cloud cover may eventually spread eastward later this
afternoon.

The bigger story, however, remains a deep Siberian low forecast
to deepen further on Sunday. This low will bring a broad front
through the southern Bering and Southwest Alaska late Sunday into
Monday. Widespread gales and even storms are anticipated over the
Bering with the front`s passage. In addition to gusty winds and
scattered precipitation over the Bering, lingering cold
temperatures and the arrival of precipitation into Southwest
Alaska late Saturday could see some light snow develop Saturday
night for the Kuskokwim Delta and Lower Kuskokwim Valley. Any
accumulations would be extremely light. The bigger concern entails
the potential for coastal flooding across the Kuskokwim Delta
coast. Persistent southwest winds into the Kuskokwim Delta coast,
timed with the fluctuation of tides, will see water levels rise
above normal highest tide. Concerns for coastal erosion as well as
potential flooding exist. A coastal flood watch issued on
Thursday remains in effect through the weekend.

&&


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

The upper level ridge stretching from the Arctic through the
Eastern Interior to the Gulf of Alaska crosses the Canadian Border
on Tuesday. A strong Arctic low moves from the Chukotsk Peninsula
into the Canadian Arctic through the forecast period. Stretching
from this down to the Aleutians low is a well developed trough
that moves to the Eastern Mainland by Thursday. Gradient remains
substantial after the trough passage, with a long slightly
cyclonic fetch extending to Eastern Asia. A well clustered GFS /
ECMWF / UKMET and Canadian ensemble carries the continuity of the
features through midweek before uncertainty rears up once the
larger features have moved on.

The surface weather map brings in a moderately strong front that
moves into Western Alaska late Monday. Widespread windy conditions
with gale force gusts and locally heavy rain marches across the
Western Bering Sunday. Areas of gale force winds continues across
the Central to Northern Bering around St Lawrence and St Matthew
Islands through Tuesday, diminishing Wednesday. This system
continues spreads over the Western Alaska coasts with the
possibilities of local coastal flooding late Monday and Tuesday.
As the front moves inland, rain becomes mixed with snow or changes
to all snow over the Interior and Northern slopes of the Alaska
Range by Wednesday. The downwind precipitation shield reduces the
chances of rain or rain and snow mixed across Southcentral Alaska
through midweek. A surface low develops on the front in the Gulf
on Wednesday, increasing the chance for rain or rain-snow mixed to
spread across Southcentral Alaska through Thursday.

&&


.AVIATION...

PANC...VFR conditions will persist. Northerly winds of 10 to 15
kt with occasional gusts up to 27 kt are expected through Friday
evening. Gusty conditions will decrease over the last 6 hours of
the TAF period.

&&


$$