Gale Warning 286, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
605 AM AKDT Sat Mar 26 2022

.ANALYSIS AND UPPER LEVELS...

The jetstream curves over a longwave ridge in the North Pacific,
with two surface lows riding along it. One surface low, located
further south in the Pacific, will impact the Aleutians and
Southwest as it tracks northward through Sunday. The other is
currently located near the Central Aleutians. Its front is
producing gusty gale-force winds and rain as it spreads across
the Bering and the Aleutian Chain. The front is beginning to
encroach on the Pribilofs and Eastern Aleutians, where low
ceilings and gusty easterly winds are setting in. Further east, a
vertically stacked low drifts near Kodiak Island. Dillingham,
Koliganek, and other locations in Bristol Bay have seen snow and
visibility reductions overnight as its front tracks across
Southwest Alaska. Behind the Kodiak low, snow showers are
streaming northwestward into the North Gulf coast. Overall, much
of southern Alaska and the Bering Sea is blanketed in clouds as
the weather remains unsettled.

&&

.MODEL DISCUSSION...

Models are coming into better agreement, though differences remain
with the low near the Aleutians for Sunday. Most models show the
low tracking just south of the Alaska Peninsula. The outlier has
been the NAM, which brings the low center north of the Alaska
Peninsula and into the Eastern Bering. While the 06Z NAM run has
kept the low center a little further south than the 00Z NAM run,
model differences continue to limit forecast confidence. The
track of the low will have major implications for whether
conditions in some areas worsen enough to meet advisory/warning
criteria. The low track will affect where strong winds set up and
how far north snow will extend, which will in turn affect where
blowing snow is expected. These factors will determine whether
products are issued for the Pribilofs, Kuskokwim Delta, and Alaska
Peninsula.

&&

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

&&

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

As one system exits, we will get a brief reprieve across the area
to start the weekend. The storm system that drove through the
Northern Gulf over the past few days dropped an incredible amount
of precipitation in parts of Western Prince William Sound up
through Girdwood. Some measurements of the SWE (snow water
equivalent) were upwards of 5 inches. That system will depart the
area to the west today. In its wake, conditions will remain
unstable with colder air and some snow showers across the Eastern
Kenai Peninsula. For backcountry enthusiasts, please see the
Avalanche Warning for the Turnagain Pass area from the Chugach
National Forest.

Calmer conditions will prevail for inland population centers
through most of the weekend. There will likely be a fair amount of
sunshine which will allow temperatures to once again warm into
the low-mid 40s for the Anchorage Bowl and Palmer. Mostly clear
skies Sat night into Sun morning will allow temperatures to cool
more than they have for the past several nights. Expect lows in
the 20s around Anchorage/Mat-Valley with single digits possible
across parts of the Copper River Basin.

The break in the pattern will be short-lived as a new storm system
will enter the Western Gulf Sun morning. Kodiak Island will be the
first place to see deteriorating conditions as this system will
track quickly from west to east. Cold air will allow for
precipitation to start as snow for Kodiak City. The question
remains how long that cold air will linger. With steady onshore
flow and March daylight, it is unlikely that there will be
significant accumulation before temperatures climb into the upper
30s and precipitation mixes with rain. The front will then push
into much of the same area that was hit by the previous storm
(Western Prince William Sound/Portage Valley). The few differences
with the upcoming storm are that temperatures will initially be
colder, which could allow for better snow accumulations.
Additionally, this system will bring higher sustained winds than
the previous system with 25 to 40 mph possible at sea level. These
gusty winds will also be able to move up into parts of Eagle
River and the Mat Valley starting Sun evening. With a southeast
direction for Eagle River, this will likely be enough to push some
light snow over the Chugach into the front range Monday morning.
The main population centers will remain downsloped with little to
no precipitation.

There remains some uncertainty regarding the
combination of winds and falling snow creating visibility issues
along the Seward Highway. At this time, it looks like period of
heaviest precipitation will coincide with temperatures warming
enough to limit blowing snow concerns. However, we will continue
to monitor this potential. QPF totals could once again reach into
the 2-4" range as the storm lingers in the same area through Mon
into Tue.

&&

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

Generally quiet weather is expected across much of Southwest for
today. Partly to mostly cloudy skies are expected with a few
isolated flurries or light snow showers mainly across the higher
terrain. Temperatures will mostly be in the mid to upper 30s
across most of the area with the mid to upper 20s for the
Kuskokwim Delta Coastline.

Tonight, moisture will increase across Southwest resulting in more
coverage area of snow showers as the first weaker upper level
shortwave moves through the area. Little to no snow accumulation
is expected with this upper level shortwave. Otherwise, expect
mostly cloudy to overcast skies with temperatures in the low to
mid 20s with upper 20s to near freezing across coastal Bristol
Bay.

Next, for Sunday, a much stronger upper level shortwave will
round the base of the upper level trough and merge/phase with the
aforementioned shortwave. This will result in a rapidly deepening
cyclone as it moves northward towards the Shumagin Islands and
then stalls Sunday evening through Monday evening before finally
moving slowly eastward through Monday night. Therefore, this
system is expected to bring a myriad of weather impacts to
Southwest from strong gusty winds, heavy snowfall (6 to 10
inches), and reduced visibilities. As a result, a Special Weather
Statement has been issued for the Kuskokwim Delta for gusty
northeast winds with the potential for blowing snow and reduced
visibilities. There remains some uncertainty still in the exact
placement of the low resulting in issues on exactly how much
precipitation makes it into the Delta. The Kuskokwim Delta
coastline has the best chance of seeing the blowing snow and
reduced visibilities. A Winter Storm Warning is in effect for the
Bristol Bay area from Dillingham north and west for blizzard
conditions and strong gusty winds with gusts as high as 70 mph
from Sunday morning through Monday morning. Strongest gusts are
expected near Koliganek to New Stuyahok.

Conditions begin to slowly improve Monday afternoon through Monday
night as the system shifts off to the east. As a result, expect
diminishing winds as well as a more showery nature to the
precipitation during this time.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through
3...Today through Monday night)...

A low pressure system currently north of Atka will continue moving
eastward reaching Dutch Harbor by this evening. This system is
bringing gale force winds with it to the southern Bering and
coastal marine waters along the Central and Eastern Aleutian
Island Chain. As a result, increased seas with wave heights of 15
to 20 feet are also expected. Mostly rain is expected in Dutch
Harbor from this system, though, some snow may occasionally mix
in.

Next, a much stronger upper level shortwave is expected to round
the base of the upper level trough and phase with the
aforementioned low pressure system. This will result in a rapidly
strengthening storm system moving from the North Pacific towards
the Shumagin Islands on Sunday. On the backside of this low, a
tightening pressure gradient is expected to develop along with
colder air moving in across much of the Bering. This in
combination with falling snow is expected to result in blizzard
conditions for the Eastern Aleutians including Dutch Harbor where
a Blizzard Warning is in effect Sunday morning through Monday
evening. There remains question as to how much precipitation
overspreads the Pribilofs to result in blowing snow issues.
However, we do have high confidence in strong gusty winds with
gusts as high as 50 mph expected. The one other area where
uncertainty still remains is the Cold Bay area where depending on
the exact track of the low will result in whether or not blowing
snow occurs. A track further west would mean a warmer scenario
whereas a track further east favors colder with blowing snow
concerns.

Lastly, another gale force frontal system with unsettled weather
is expected to move through the Western Aleutians Sunday night
through Monday.

&&.Marine (Days 3 through 5: Monday through Wednesday)...

Gulf of Alaska: A weakening low moves across the Southern Gulf
and its front moves to the Northern Gulf for Wednesday. Forecast
confidence decreases. Gales with the front move to form a high end
gale force barrier jet along the North Gulf Coast, and through
Cook Inlet and Shelikof Strait diminish late Monday. Areas of
storm force winds through the Barren Islands and Kamishak Bay for
Monday. Seas to 16 feet with the front through Tuesday, and to 14
feet across the Southern Gulf through Wednesday.

Bering Sea: A weakening low along the Alaska Peninsula moves into
the Gulf, and its front extends over the Southeast Bering through
Tuesday. A strong front stretches from a well developed Kamchatka
low across the Aleutians and Bering through Wednesday. Forecast
confidence decreases. Northerly high end gales over the Central
and Eastern Bering moves across the Alaska Peninsula late Monday.
Seas to 20 feet on the Bering side, subsiding. Freezing spray over
Southern Bering ice free waters. Widespread high end gales with
the low and front moves to the Central Aleutians and Bering,
diminishing Wednesday. Seas to 20 feet in the Western Bering,
subsiding, but persisting along the Pacific side through
Wednesday.

&&

.Long Term Discussion (Days 4 through 7: Tuesday through
Friday)...

A broad frontal system over the Bering combined with multiple
upper-level troughs later next week will usher snow and
potentially snow/rain mixed and periods of gusty winds over much
of the Aleutians, Bering and Southwest AK. An amplified low
connected to the aforementioned front will move slowly across the
Bering which will aid to spreading increased low clouds and
additional precipitation over the Aleutians and Southwest Delta
Coast. While most models indicate a brief period of gales
offshore Tue morning, the potential for widespread gales is
favorable given the motion and how this pattern will play out, but
will wait for future ECM and GEMR solutions to see whether they
will pick up the winds in comparison to GFS. In fact, GFS is by
far the most aggressive of the rest.

At Southcentral, an upper low over the Gulf will send a few strong
upper waves toward Southcentral but mainly concentrated over
Prince William Sound Tue morning through Wed afternoon.
Precipitation from this event could reach Anchorage Bowl and Matsu
Valley while the heaviest precipitation is expected east of
Anchorage Bowl. A transient upper ridging will pass through
Southcentral between Wed night and Thu night, and this could
either delay or speed up the arrival of a trailing upper trough
from the eastern Bering. There is uncertainty with the timing of
the latter feature over the Gulf, for this will wait until most if
not all the solutions jump on the same sheet of music for this
next expected feature.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning: 185.
         Winter Storm Warning: 161.
         Winter Storm Watch: 195.
MARINE...Gales: 130-132, 136-138, 150, 155, 160, 165, 170-177,
		 		179, 180, 352, 412-414.
         Heavy Freezing Spray: 179.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KC
SOUTHCENTRAL ALASKA...MO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MV
MARINE/LONG TERM...KZ/CB