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000
FXAK68 PAFC 271304
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
504 AM AKDT Wed Sep 27 2023

.ANALYSIS AND UPPER LEVELS...

Two troughs, one over the western/central Bering and another over
the Gulf of Alaska are separated by shortwave ridging over
Southwest Alaska. An occluded low over the western Bering is
bringing low-end to moderate winds and rain over much of the
Bering Sea and Aleutian Chain, while the ridge keeps conditions
mostly clear, dry and cool over Southwest. Over Southcentral,
cloudcover has increased as troughing becomes more prevalent over
the area. A few showers have developed in the Prince William Sound
and eastern Chugach. Due to cloudcover, temperatures over
Southcentral are slightly warmer than those observed yesterday,
though plenty of areas in the 30s and even upper 20s remain where
skies are clear.

&&

.MODEL DISCUSSION...

Models are in good agreement overall and have come to a better
consensus in regards to a stronger system impacting the Southern
Mainland this weekend. Most notably, the system is slower to
reach waters south of the Alaska Peninsula on Saturday, which
will allow it to phase with a shortwave and colder airmass
arriving from the Bering Strait on Sunday. Previous solutions had
a more progressive system and less phasing. This will result in a
more prolonged precipitation event and possibly snow for interior
areas early next week.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

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

Beautiful Fall weather will continue today and Thursday before a
system moving north and east along the Eastern Aleutians and
northwest Gulf of Alaska brings a return to a cloudy and wet
pattern beginning on Friday and continuing into the weekend.
Mostly clear skies will continue with only high clouds expected
today and again on Thursday with heavier cloud cover expected over
the Copper River Basin. That cloud cover has moderated morning
low temperatures over the Copper River Basin by nearly ten degrees
over yesterdays lows in the teens. Expect high temperatures today
and Thursday to reach into the upper 40s to near 50 again in
Anchorage and Mat- Su Valleys as high clouds take a few degrees
off of yesterday`s high temperatures. Lows tonight will mainly be
in the 30s. The only real feature of note remains a low spinning
over the far eastern Gulf with inverted trough extending to the
northwest of the low along the northern Gulf coastline. The low
will gradually weaken over the next few days, but with another
ridge starting to move towards the AKPen from the west...enough of
a pressure gradient will develop to allow for Small Craft and
Gale force gap winds through the Barren Islands.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

The western Bering low continues meandering eastward towards
Southwest Alaska through the end of the week. Southwest Alaska
will continue to experience relatively relaxed conditions today,
thought cloud cover and rain will begin to filer in west to eat
this evening. Light rain spreads inland through Thursday with
increasing southerly winds as the low center tracks near the
Yukon-Kuskokwim Delta. Thursday night, the low weakens, allowing
winds and rain to diminish. A stronger North Pacific low
approaches the Aleutians for Friday, where winds will increase to
gale force out of the east, accompanied by light to moderate rain.

&&

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

The long term period begins on Saturday with a longwave trough
over Southwest Alaska. The jetstream is forecast to be well south
of the Gulf coast and directed northeastward into Southeast
Alaska. Models are in reasonable agreement with the placement of a
broad upper low immediately south of the Eastern Aleutians and
Alaska Peninsula. A hefty front is progged to stretch from Bristol
Bay into the Gulf of Alaska offshore zones. Widespread showers
are likely to be ongoing over the southern Bering and Aleutians
with precipitation extending into all of the Gulf of Alaska.
Multiple shortwaves will be rotating around the low, helping the
low to dig eastward into the Gulf with a front moving onshore of
the Gulf coast through Sunday night. As such, a threat for heavy
rain will exist from Kodiak Island, along the coast, including
Prince William Sound, into Southeast Alaska over the weekend, as
plentiful moisture is funneled into the region.

A second upper low is forecast to dig southward across the
eastern Bering through Sunday night. While renewed precipitation
chances are forecast for the Aleutians, as well as Southwest
Alaska, the bigger story may be the amount of cold air spreading
southward behind the low. Models are indicating potential 850 mb
temperatures ranging from -8 to -10 degrees. This cooler air mass
spreads from the Kuskokwim Delta and into Southcentral and the
ALCAN border through Mon night. It is entirely possible that
portions of the Kuskokwim Delta and the Lower Kuskokwim Valley may
see snow develop late Monday night into Tuesday of next week.


&&

$$

SYNOPSIS AND MODEL DISCUSSION...CJ
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
LONG TERM...BL