Gale Warning 242, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
631 PM AKST Fri Mar 4 2022

.ANALYSIS AND UPPER LEVELS...

A strong surface low is moving north over Norton Sound this
afternoon. Gusty southwesterly winds wrapping underneath the low
continue to across the Southwest coast, with gusts this morning
peaking between 50 and 60 mph from Kipnuk south to Togiak. A peak
gust of 87 mph was reported earlier this morning at Cape
Newenham. The strongest winds are now over the Kuskokwim Delta.
The winds, combined with snow that has already fallen and bands of
snow lifting south to north, have reduced visibilities at times
across parts of the Kuskokwim Delta to as low as one quarter mile.

Farther east, the tight pressure gradient between the low and a
ridge over the Gulf is also allowing for gusty southeasterly gap
winds to maintain their strength from Palmer down to Turnagain Arm
this afternoon. As of noon, the winds are reaching their peak,
with gusts over 60 mph for some locations along the Upper Hillside
of Anchorage and 45 mph at the Palmer Airport. Widespread
precipitation (coastal rain/snow and inland snow) is also falling
from Prince William Sound to the Susitna Valley, ahead of an
occluding front. The southeasterly cross-barrier flow aloft is
keeping the bulk of this precipitation away from the lee of the
Kenai and Chugach Mountains. A new surface low is currently
developing along the front east of the Barren Islands.

Elsewhere, another surface low is lifting north across the Eastern
Aleutians with a rain/snow mix and gusty southeasterly winds for
Unalaska. A ridge sits over the Western Aleutians and Bering with
generally tranquil weather conditions. Two separate surface lows
are also situated well south of the Aleutian Chain. The first is
south of Attu and is moving north. The second is well south of the
AKPen. This low has good upper level support as it sits in the
right entrance region of a strengthening 100 kt jet streak.

&&

.MODEL DISCUSSION...

Models are in good agreement with with the overall synoptic
pattern with respect to the next storm system moving to
Southcentral for Saturday. There are some discrepancies, though,
and these continue to manifest in the speed at which the upper-
level trough and associated surface low move to the northeast
from the western Gulf. The biggest challenge is that each
individual model has had decent run to run consistency, but that
agreement between models still show differences. The NAM remains
the fastest solution with the GEM regional and other hi-res models
lagging slightly behind, albeit slightly slower than previous
runs. The EC is the the middle and GFS and Canadian still the
slowest, keeping precipitation lingering across the Anchorage Bowl
through Sunday morning. Confidence remains high regarding a
widespread snow event for Southcentral. However, confidence in
snow amounts has not improved. The current forecast is weighted
toward the faster solutions. However, if trends begin to favor the
slower solutions, forecasted snow amounts may have to be adjusted
upward.

&&

.AVIATION...
PANC...Southeasterly wind gusts will gradually diminish through
the late afternoon and evening hours. Winds will then become light
and variable overnight, turning northeasterly by Saturday morning.
VFR conditions are expected though early morning Saturday before
ceilings begin to lower. MVFR conditions are expected after 15z
with light snow developing. IFR conditions are then expected by
mid-morning and continuing through Saturday afternoon with snow.

&&

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

Southeasterly winds will begin to diminish tonight ahead of an
approaching trough that will bring more precipitation across the
area. Precipitation is expected to remain mostly wet snow or a
rain and snow mix during the afternoon. Intensities may increase
throughout the afternoon. Models have aligned a little better with
the trajectory and a broadening of the trough near Prince William
Sound Saturday afternoon. Some disagreement in the timing of the
low, but most of the models appear to have some agreement in wrap
around precipitation and lingering snowfall in the Anchorage area,
especially for higher elevations near Eagle River and the
Hillside. Northwesterly winds, plenty of moisture, and cold air
advection on the tail end of the low could enhance upsloping snow
and potentially raise some of the snow ratios before completely
diminishing. The shift in the weather pattern along with greater
confidence in higher snow totals along the Hillside has lead to a
Winter Weather Advisory. North of Gakona, especially near Paxson,
will also have snowfall around approaching 10 inches with locally
heavier amounts and opted for an Advisory in the northern areas of
the Copper River Basin. As winds increase Sunday morning, blowing
snow and reduced visibility is also possible near Isabel Pass.

A brief ridge will build behind the trough. Cold air advection
along with efficient cooling from skies clearing will allow for
gap winds to increase Sunday afternoon. A developing North Pacific
low will press through towards the western Gulf on Sunday night
and although there is better agreement, there is still enough
uncertainty in the forecast beyond Monday morning for the onset of
another wave of precipitation nearing Kodiak Island Sunday night.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 to 2 - This
afternoon through Sun night)...

A shortwave trough producing a compact low pressure system will
move across the eastern Bering tonight and move towards Bristol
Bay by Saturday morning. This weak system will bring snow showers
to the area. Additionally, a low pressure system will move into
the western Gulf towards Saturday morning and help to produce an
area of light snow across western parts of Bristol Bay. Both of
these systems will produce little to no snow accumulations. By
Saturday night and Sunday these systems will clear the area and be
replaced by high pressure with cooler temperatures. As skies
clear and winds become light Sunday night and Monday morning fog
is expected to develop across the Kuskokwim Delta. By Sunday night
another low pressure will move towards the AKPen with increasing
winds and chances of rain and snow for the AKPen. However, there
is model uncertainty with this next low, so stay tuned as we
update the forecasts.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 to 2 - This
afternoon through Sun night)...

A compact low pressure north of Cold Bay will track towards
Bristol Bay. This will produce a small area of gales mainly on
the south side of the low. Otherwise, a storm force low and front
will move across the Western Aleutians tonight and then into the
western Bering Saturday this will bring a short period of snow
changing over to rain. This low will slowly track north and weaken
on Sunday, but will continue to produce gales across portions of
the western Bering. A north Pacific low will move towards the
AKPen Sunday night with gale force winds possible near the AKPen
and eastern Bering. However, model uncertainty exists with this
low so forecast could change. Stay tuned.

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

Gulf of Alaska: A moderately strong North Pacific low moves over
Kodiak Island, as its front extends across the Gulf through
Wednesday. Forecast guidance is good. High end northeast gales
stretch from the northern Gulf around Kodiak and Barren Islands,
Shelikof Strait and the Alaska Peninsula coast, diminishing. Seas
to 16 feet across the southern Gulf, subsiding Tuesday. Areas of
gusty winds persist through Wednesday.

Bering Sea: A northern Bering low continues into the Chukchi Sea
by Tuesday. A well developed low and front moves into the Bering
through Wednesday. Forecast guidance is good. Gusty southerly
winds across the northern Bering diminish. Seas in ice free
waters to 12 feet, subsiding. The wind wrapped western Bering low
and front brings high end southerly gales with areas of storm
force winds over the Aleutians and across the Bering, spreading
into the Central Bering for Wednesday, diminishing. Seas building
to 30 feet in parts of the Western Aleutians and Bering by
Tuesday, subsiding Wednesday.

&&

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

The long term begins Tuesday with a continuation of an amplified
upper-level pattern. A large upper-level ridge dominates the
eastern Pacific and extends north along the Al-Can border. A
large upper-level trough remains situated over the Western
Aleutians. By Wednesday, the ridge is pushed south as a shortwave
trough ejects from the larger trough and moves toward
Southcentral. A second shortwave also drops south from the
northern Bering, allowing a trough to linger across the state
while the ridge reasserts itself over the eastern Pacific and
extends across the AKPen and into the eastern Bering. The long-
wave trough upstream becomes negatively tilted as a large upper-
level ridge builds over eastern Russia. Although models diverage
greatly through next week, they are all indicating the potential
for the establishment of a rex block, with the ridge centered near
the Bering Strait and a trough with multiple embedded shortwaves
positioned along the Aleutian Chain by the end of next week. As
for sensible weather, expected near normal temperatures through
the period with a chance for snow over the interior and a mix of
rain/snow along the coast Tuesday into Wednesday as the
aforementioned shortwaves coverage on Southcentral. Conditions
will remain unsettled across the Aleutians as a series of lows
rotates around the larger upper-level trough.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory: 101 141.
MARINE...Storm: 175-178 411 413.
		 Gale: 119 130 173 174 185 412.

&&

SYNOPSIS AND MODEL DISCUSSION...TM
SOUTHCENTRAL ALASKA...VR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RC
MARINE/LONG TERM...KZ/TM