Gale Warning 731, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
354 PM AKST Sat Nov 25 2023

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

A highly progressive pattern is expected this forecast period. A
cold low near Cold Bay will become a trough and continue to eject
shortwave energy into Southcentral and keeping southerly flow on
tap. The trough axis will push eastward pumping Pacific moisture
towards the region. The main fetch of moisture will impact Prince
William Sound. Surface temperatures will vary across Southcentral
and the precipitation type will vary. After the upper level trough
exits Southcentral, an occluded front from the Bering will push
over Kodiak and into the Gulf. On satellite imagery, this system
also has a fetch of modified tropical air entrained into it.
Expect another round of precipitation.

&&

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

Key Messages:

 - Models are in poor agreement resolving where a triple point low
   will form along an occluding front tracking across the Bering.
   This is leading to overall lower forecast confidence for Sunday
   into next week.
 - There is a low chance (20% to 30%) that ice could pile up along
   the shore across the Kuskokwim Delta (specifically Kipnuk to
   Kongiganak) Sunday into Sunday night.
 - There is a low to moderate chance (30% to 45%) that coastal
   flooding could occur across the Kuskokwim Delta shoreline
   Sunday into Sunday night.
 - Temperatures will trend cooler through the weekend and into
   next week.

Discussion:

The front of a Kamchatka low will continue to sweep across the
Bering with it's southerly gale-force winds reaching the western
coast of Alaska by Sunday morning. Confidence is high that this
front will bring gale-force wind, with localized areas of embedded
storm force wind. Behind the aforementioned front, strong cold
air advection will bring gusty westerly winds following the front
through this weekend and into next week. One challenge with this
front, and an area where where model variation is greatest, is
identifying where a triple point low will develop along the
occluding front. Any developing low will lead to increased winds
in their immediate vicinity, increasing the complexity of
forecasting where stronger winds will occur. This impacts where/
if areas could see potential ice could pile up along the shore/
coastal flooding.

The front is expected to reach the Pribilof Islands by Saturday
night and then the Southwest coast by Sunday. With this front,
heavy to moderate precipitation will fall across the Chain but
then lose steam as the front weakens bringing light precipitation
to Southwest, with the exception of the Bristol Bay region
receiving moderate precipitation. Temperatures across the entire
region will trend downward through this weekend and into next week
as colder air builds in behind the front. Rain is more likely to
linger along the coast than toward the interior, but even there
temperatures in most locations will decrease enough behind the
front for rain to transition into snow by Monday.

-Sprinkles

&&

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

A well developed North Central Bering low moves towards the
Western Alaska coast, extending the longwave trough across the
Southern Mainland Alaska. This trough will dissipate Thursday over
Western Interior Alaska. The trough brings widespread cooler
temperatures across the region through the forecast period, with
areas of heavier precipitation. Higher surf may occur over the
Yukon- Kuskokwim coasts. Further west, a second strong low near
Southern Kamchatka brings a major shortwave trough across the
Aleutians and Bering towards Southwest Alaska, with weaker
shortwave troughs to follow along the Aleutians and Alaska
Peninsula. Large areas of gale force winds are expected to spread
along the Aleutians and Alaska Peninsula through the end of the
period. Forecast confidence for tracks and strengths becomes mixed
through Saturday with the transient lows.

A strong Eastern North Pacific low moves into the Gulf of Alaska
through Saturday. A gale force barrier jet occurs along the North
Gulf Coast, diminishing late Thursday. Gusty winds up to gale
force will spread mostly over the Eastern Gulf, diminishing
through Saturday. Widespread areas of mixed precipitation are
expected along the North Gulf Coast, and spread inland through
the period.

Kutz

&&

.AVIATION...

PANC...VFR conditions are expected to prevail for the remainder of
the afternoon and into the evening and then deteriorate to MVFR by
Midnight. Rain coverage will increase for Anchorage again this
evening into the overnight as a set of troughs rotate northward.
Modest cold air advection will slowly result in rain changing over
to snow or a rain/snow mix through the day on Sunday before
changing over to all snow by Sunday afternoon should any
precipitation remain in the area. Ceilings will gradually lower
through Saturday night with some IFR CIGs possible Saturday
morning.

Conditions may improve late Sunday before another trough brings
snow and likely IFR conditions to Anchorage late Sunday night into
Monday.

&&