Gale Warning 292, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
452 PM AKDT Wed Mar 25 2020

.ANALYSIS AND UPPER LEVELS...
An upper level trough and low center over the eastern Bering Sea
is tracking southeastward toward the Gulf of Alaska. Meanwhile, a
separate short-wave trough is dropping southward across northern
Alaska. The combination of these two features is producing
widespread light rain and fog over Southwest Alaska. Temperatures
are hovering around or a little above the freezing mark, so there
could be some patchy freezing rain out there, but no ice
accumulation is expected. As the upper trough over northern Alaska
approaches Southcentral, light snow is falling across portions of
interior Southcentral, primarily from the Mat-Su to the Copper
River Basin. Westerly low level flow is focusing snow along the
western slopes of mountains, most notably the Talkeetna Mountains
and Wrangell Mountains. Dry, but cloudy conditions prevail as you
head south to coastal Southcentral.

Out west, a ridge of high pressure over the central Bering Sea is
producing benign conditions across the heart of the Bering Sea and
along the Aleutian chain. A weak low is tracking up the west side
of this ridge, with a front approaching the western Aleutians.

&&

.MODEL DISCUSSION...
Models are in good agreement with handling of large scale features
over the next few days and forecast confidence is above average.
One of the primary forecast challenges will be snow accumulation,
which often becomes more difficult to forecast this time of year
with marginal surface temperatures (near or above freezing).

&&

.AVIATION...
PANC...VFR conditions and light winds will persist. There may be a
brief period of low end VFR conditions (between 3000 and 5000 ft)
this afternoon with light snow over the mountains, but ceilings
will quickly lift this evening as drier and cooler air advects in
from the north.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

A moist trough moving through the region this afternoon has
brought showers to the area. Temperatures have generally been warm
enough for rain across the Anchorage Bowl and Mat-Su Valleys,
though as showers continue into the evening, a change to a
rain/snow mix is possible. Little to no accumulation is expected.
As the trough exits overnight, strong northerly winds will pick up
along the northern Gulf coast for Thursday. Locations including
but not limited to, Seward, Valdez, and Palmer will see locally
elevated winds. These winds will likely peak Thursday night before
tapering off Friday morning. The next chance for precipitation
will be Friday afternoon as another system approaches Southcentral
from the west.

&&

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

A weak low moving southeast across Bristol Bay this afternoon
continues to keep plentiful moisture and low clouds over the area.
The rain ongoing across much of the Bristol Bay land zone will
move south and exit the area during the evening hours tonight.
With generally light winds expected across the area tonight,
widespread fog and low stratus are expected to develop and persist
over nearly all of the lower elevations of Southwest Alaska, with
perhaps some clearing in the northern Kuskokwim Valley. This
should allow temperatures to fall into the 20s tonight in the
Kuskokwim Valley with temperatures holding near freezing across
Bristol Bay. Generally quiet weather is expected on Thursday, with
the sun returning to the Lower Kuskokwim Valley and Bristol Bay.

The next front moves into Southwest Alaska Thursday night. By
then, with colder air having moved into the Kuskokwim Valley, much
of Southwest Alaska will get snow with this round. Fortunately
with the front moving relatively quickly, and some of the snow
expected during the day Friday, accumulations are expected to be
minor, on the order of 2 to 5 inches. The highest accumulations
will be over the Kuskokwim Delta. Then on Friday night, a low
tracking along the front will move into the Kuskokwim Delta.
Behind the low, much colder air moves into the region. Snow
showers will be common into Saturday, but will diminish with time.
There is some concern that ocean-effect snow showers along the
coast could reduce visibilities and produce heavier snow for a
time in coastal communities. A return to winter-like temperatures
is expected area wide through the weekend.

&&

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

A front approaching the western and central Aleutians right now
will sweep northeastward across the Bering through Thursday
night. As the front runs into colder air over the northern Bering
Thursday, a low will develop along the front which will move into
Southwest Alaska Friday evening. High pressure will move over the
Aleutians through Friday. Behind the low, much colder air spilling
southward will cause a return to freezing spray conditions over
the eastern Bering, and by Saturday on the Pacific side of the
Alaska Peninsula. Meanwhile a weak low will move across the
central and eastern Aleutians on Saturday as a separate front
moves into the western Aleutians Saturday afternoon.

&&

.MARINE (Days 3 through 5/Fri through Sun)...

The main focus for Friday will be a low tracking into Southwest
Alaska with strong northerly flow and cold air advection on the
back side. Confidence is high in widespread gale force winds,
with potential for storm force gusts through gaps of the Alaska
Peninsula Friday night through Saturday. The colder air will also
reintroduce the likelihood of heavy freezing spray across the
eastern Bering and along the Alaska Peninsula. The stronger winds
and freezing spray will also likely move into the western
Gulf/Kodiak Island area as well. There is also a moderate to high
degree of confidence in large short period seas east of Kodiak on
Saturday as the southwesterly seas oppose the northeasterly
currents.

Another storm system will makes its way into the western to
central Bering Sea on Sunday. While there is some uncertainty
in the track of this storm, it looks like winds will top out at
small craft or min gale with this storm.

&&

.LONG TERM FORECAST (Days 4 through 7/Sat through Wed)...

There is a high degree of continuity between guidance that an
upper level trough will move over the western Alaskan mainland on
Friday. This upper trough will result in colder temperatures
across the Alaskan mainland this weekend. Significant differences
between guidance begin to arise on Sunday. The only area where
there is a moderate degree of continuity between guidance is the
upper trough is over the southeastern mainland near the AlCan
border while an upper ridge moves in from the Bering towards the
Alaskan mainland. Temperatures are expected to rebound early to
middle next week. However, significant amplitude differences are
evident with respect to the upper ridge and therefore the forecast
confidence in the magnitude of temperatures rebounding is very
low. For the remainder of the forecast period, confidence remains
very low as significant discrepancies arise between guidance with
respect to the placement of upper level features which in turn
effects the placement of surface features.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE: 130 179 411 412.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SB
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...ED