Brisk Wind Advisory 43, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
357 PM AKDT Sat Mar 25 2023

.ANALYSIS AND UPPER LEVELS...

High pressure is over Southcentral Alaska this afternoon and a
cold front is over the Bering Sea and heading into Southwest
Alaska. The surface low center is in eastern Russia and weakening
as it moves to the northeast. The warm front is what is tracking
across Southwest Alaska this afternoon bringing in the cloud
cover. The main precipitation in Southwest will be ahead of the
cold front which is still out in the Bering Sea.

The upper level ridge is over Southwest ALaska this afternoon with
the jet stream running up the ridge to the west and then giving
stiff northerly flow over the north Gulf coast. This northerly
slow is helping to kick up the gap winds for the usual suspects:
Seward, Whittier, and Valdez. These winds are also enhanced by the
surface low that can be seen southeast of Cordova on satellite and
moving to the southeast. Winds will diminish as this low pulls
away from the area and the ridge axis moves over Southcentral
Alaska and brings light flow aloft underneath it.

&&

.MODEL DISCUSSION...

Models are in quite good agreement into the middle of next week
when there will be some questions in regards to where a triple
point low develops south of Kodiak and moves into the Gulf.
Other than that, there really is not much else to say about them.

&&

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

&&

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

A stretch of calm, dry and at least partly sunny conditions will
set in for the rest of the weekend into early next week as a
strong upper ridge builds the southern Mainland through Monday.
In the near term, strong and gusty gap winds along the coastal
mountains surrounding Prince William Sound will diminish overnight
into Sunday morning as a low and attendant shortwave near Yakutat
exit to the south and as strong northerly upper level flow and
cold air advection both diminish as the ridge axis moves right
overhead. Precipitation chances will remain minimal on Monday,
but cloud cover will begin to pick up as a weak shortwave moves
northeast into the Cook Inlet region ahead of a frontal system
moving across Southwest. The main upper level trough following
the then weakening front will cross the Alaska Range into
Southcentral by Monday night as flow shifts to a more west-
southwest orientation, bringing back chances for light snow
from mainly the Anchorage area north towards the Susitna Valley.
However, the mostly westerly upper winds along with the weakening
nature of this system will limit chances for much more than
flurries, with the best chances for light snow focused towards
the Talkeetna Mountains late Monday into Tuesday morning.

&&

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

High pressure overhead will slowly progress eastward toward
Southcentral as a front pushes ashore over the Kuskokwim Delta
tonight. The aforementioned front will eventually stall over the
region and lead to a persistent onshore southerly flow. This will
drive warmer temperatures into the area and change precipitation
to a rain/snow mix or plain rain. Areas where rain falls onto
frozen ground/snow will act as an icy surface, but meteorological
freezing rain is not anticipated due to the amount of warm air
being pushed into the region tonight. The question comes later
Sunday night as colder air trails along behind the frontal passage
and pushes into Southwest as precipitation is still expected to
be falling. The main area of concern is Dillingham north and west
as the potential for freezing rain could occur. However, the
thought with this forecast package is that their will not be a
strong enough warm nose/inversion to make this a reality. As such,
a rain/rain snow mix is forecasted for that area. Further north
across the Kuskokwim Delta, precipitation will transition to snow
Sunday night and produce new snowfall amounts of 1 to 3 inches.
Additionally, gusty southwesterly flow that accompanied the
frontal boundary as it first made it's way over Southwest will
diminish by late Sunday morning, while the flow remains largely
southwesterly until Monday morning when the flow shifts westerly.
Later into Monday afternoon, the once stalled front resumes its
eastern progression, moving more into the Greater Bristol Bay
area, however the organization of the system is expected to have
diminished significantly by this point and associated precipitation
will likely become showery snowfall. Heading into Tuesday a weak
transient ridge will begin to build back into the area to promote
clearer skies and cooler temperatures.

&&

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

The pattern remains amplified with an upper-level ridge building
over the Southwest and an upper-level trough digging into the
western Bering. Tightened pressure gradients between these two
features has translated to a swath of gale force winds in the
eastern Bering progressing eastward throughout tonight. A front
in the eastern Bering associated with a low in the Chukchi Sea
continues to track across the Bering west to east and will reach
the Southwest tonight. Ahead of the front, warmer southerly flow
continues to increase temperatures across the eastern
Bering/Aleutians through at least Sunday night before westerly
colder air begins to slowly track back into these aforementioned
areas. Rain/snow will begin to diminish in the Pribilof Islands
late Sunday morning. Unalaska will begin to see precipitation by
late Sunday night/Monday morning. It is by this point that the
organization of the frontal boundary begins to deteriorate. Rain
and snow showers will become more common as the remnants of the
frontal boundary move over the western Alaska Peninsula by Monday
night. However, a new low pressure system appears to approach the
western Bering/Aleutians by Monday afternoon. Southerly flow and
an increase in temperatures will promote another transition to
rain as the predominant precipitation type as the aforementioned
low approaches Amchitka by Tuesday morning.

&&

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

The upper level pattern will remain amplified and have the
general trend of upper ridging over the Bering/Aleutians and
troughing over southeast Alaska. The biggest story will be a
surface low moving from Bristol Bay into the northern Gulf of
Alaska Wednesday and Thursday. Confidence is low in the exact
track of this system at this time. This low is expected to bring
precipitation to parts of Southcentral. However, precipitation
type and amounts will depend on the track of this low. A more
southerly track will result in greater chances for snow along
the Kenai Peninsula while a more northerly track will increase
the chance that snow may mix with and/or change to rain.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: Copper River Delta nearshore, Kuskokwim
Delta Coast, Pribilof Islands, Eastern Aleutians and Alaska
Peninsula Bering side outer waters.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...AS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS
LONG TERM...ED