864
FXAK68 PAFC 230100
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 PM AKDT Sun Sep 22 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA
(Days 1 through 3: This afternoon through Wednesday evening)...

Expect clouds to continue to increase for the entire region the
rest of today with Kodiak seeing rain much of today. This rain
spreads to the north Gulf coast through the remainder of this
afternoon and into this evening. While this low will bring
widespread Gale force winds to the Gulf, with some Storm force
winds in the barrier jet that will develop overnight along the
north Gulf coast, this low will rapidly weaken as it moves into
the northern Gulf on Monday. However, it will be slow to leave the
area, remaining quasi-stationary into Wednesday. That leaves the
next few days with rain along the north Gulf coast and showery
conditions in the Lee of the mountains. While cross barrier flow
tonight should cut off most of the steady rain from moving too
far inland, upper-level waves will continue to move overhead and
provide some lift to squeeze out light rain showers late tonight
into Monday morning. This flow looks to weaken through Monday and
Tuesday and help to continue showery conditions across Anchorage
and the Western Kenai Peninsula. The majority of rain stays along
the north Gulf Coast, Prince William Sound, and the Eastern Kenai
Peninsula for Monday and Tuesday. For Wednesday, most of the area
continues to remain within cyclonic flow and thus will continue to
see cloudy conditions with most of the showery activity confined
to the coast.

&&


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

The center of a vertically stacked low, roughly 60 nautical miles
south of Chignik, continues to track eastward and out of the
region this evening. A look at the broader synoptic pattern shows
general troughing will remain over interior Alaska with high
pressure lingering across the western Bering through Tuesday.
Cooler conditions are forecast across both the Bering and
Southwest Alaska as northerly flow is directed into the Eastern
Aleutians and Alaska Peninsula.

In the short-term, showery conditions are noted on radar across
much of the Greater Bristol Bay area. These should gradually
diminish through tonight with the departure low pressure to the
east. Monday into Tuesday mostly drier weather is anticipated for
Southwest Alaska. Morning low temperatures will lower into the low
to mid 30s. While a few showers will be possible during the day
on Monday, within weak northerly flow, the bulk of any
precipitation should largely be confined to the higher elevations.

From the Pribilof Islands into Southwest Alaska, very little
change is forecast on Wednesday as a broad trough is forecast to
remain over Southcentral Alaska. While not a strong signal,
forecast models do hint at some light snow potential across parts
of the Lower Kuskokwim Valley down through Iliamna with Tuesday`s
and Wednesday`s morning low temperatures near freezing. The better
chance for any precipitation and snow would likely be on
Wednesday morning as the development of weak deformation oriented
from Sleetmute down into Iliamna is possible.

The next upper low will emerge from Asia into the western Bering
late Tuesday into Wednesday. An attendant front may reach the
Western Aleutians by Wednesday afternoon with renewed shower
activity and perhaps some gustier winds with any cold air
advection behind the arriving low.


BL

&&


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

Broad longwave troughing over the Gulf of Alaska and subsequent
ridging over most of the Bering Sea will persist from the start of
the extended period into Friday morning. Unsettled weather will
be experienced by most of Southcentral while portions of Southwest
near the coastline could remain dry as cold and dry air moves in
from the north. By midday Friday, a new shortwave low enters the
western Bering and tracks southeastward towards the North Pacific
by the middle of the weekend. The shortwave phases with the upper
level trough on Saturday, jetting moderate precipitation towards
Kodiak Island and much of the gulf coast into Sunday.

While a week out, a system that currently has our attention is a
subtropical Pacific low that will move northwards towards the Gulf
of Alaska. Most ensemble and operation model guidance is trending
towards a stronger system moving towards the gulf, but the
mechanisms in place to get it there vary by model. While there is
not major concern for heavy rainfall, unusually strong winds for
the gulf are not out of the question at this point in time.
Continue to follow the forecast for continued updates on this
system.

&&


.AVIATION...

PANC...VFR conditions and light winds will persist. A strong
occluded front will lift northward across the Gulf today which
will lead to increasing winds across the Kenai and Chugach
Mountains. However, strong down-Inlet pressure gradients will keep
these winds away from the terminal, except for a short window of
opportunity from 23/05Z-11Z with gusts to 20 kts.


&&


$$