Gale Warning 264, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKDT Wed Mar 22 2023

.ANALYSIS AND UPPER LEVELS...

A negatively tilted upper level trough extends from the Northern
Bering Sea into the Western Gulf of Alaska. The primary upper
level low and attendant surface low are over Kodiak Island with a
strong front bearing down on the Prince William Sound. With the
slow moving nature of the front hefty snow accumulations can be
seen on webcams and surface observations throughout the Western
Prince William Sound. Blizzard conditions persisted through mid
afternoon along Portage Glacier Road and areas surrounding
Whittier, but have improved slightly since as the precipitation
and winds both begin to diminish. Winds are calmer through the
mountain valleys, but snow is also producing areas of low
visibility throughout the Seward Highway corridor. A deformation
band can also be seen northeast of the low center extending from
Koliganek to southern Bristol Bay. Over the Bering Sea, zonal flow
and cold air aloft continue to stream snow showers into the
eastern Aleutians and Alaska Peninsula.

&&

.MODEL DISCUSSION...

Models are in good agreement in the short term on mesoscale and
synoptic features. Some locational differences exist on a small
but strong low moves into the Y-K delta tomorrow and whether winds
and snow will be coincident and strong enough to produce blowing
snow. The upper level trough associated with this low is expected
to cross the state on Friday, but the north/south location and how
far south the trough is able to dig remains uncertain. This will
impact the precipitation forecast for Southcentral.

&&

.AVIATION...

PANC...VFR conditions will persist. Occasional southerly wind
gusts may move over the terminal; however, southerly winds are
expected to diminish and become light and variable by late
evening. Some light snow may move over the terminal late this
afternoon, which may briefly lower visibility to MVFR, but this is
overall a low probability.

&&

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

An occluded low has pushed just east of Kodiak Island this
evening. Northwest winds downsloping into Kodiak City have been
keeping much of the precipitation as rain, with the bulk of snow
limited to Kodiak Island's western shores. Akhiok has had
persistent snow throughout the day with occasional rain mixing in
with the snow. Subsequent visibilities have been at or below 2
miles for much of the day. As colder temperatures continue to
filter in from the northwest, any lingering rain should change
over to all snow. Off and on snow showers are then expected to
taper off from south to north across Kodiak Island through
midnight as the occluded low gradually lifts further northeast
into the Gulf.

It has also been an active day across Western Prince William
where the occluded low's front continues to lift northward across
the Kenai Peninsula with snow and elevated winds this evening.
Heavy snow and gusty winds did not disappoint with locations from
Whittier into Turnagain Pass experiencing whiteout conditions at
times. The city of Portage had a peak wind gust of 77 mph earlier
in the day, though winds have finally begun to wind down this
evening despite continued snowfall. Heavy snow has been observed
all the way down the Seward Highway corridor as well with the city
of Seward reporting over a foot of snow. Through the rest of the
night snow and winds will eventually come to an end as the
northward moving front gradually weakens and shifts off to the
east through early Thursday morning.

For Friday, a polar trough will skirt the northern fringe of
Southcentral with the resulting thermal gradient to help induce
cyclogenesis over the Susitna Valley. Redeveloping snow showers
will be possible from the Talkeetna's into the Chugach Mountains
as the low dives southward into the Gulf Friday afternoon through
Friday night. Light snow will be possible over the Mat-Valley and
Anchorage Bowl and also into the Copper River Basin and Prince
William Sound areas over the second half of the day into Friday
night. Any low elevation accumulations should be light with
heavier snow confined to the higher elevations. Finally, cold air
advection from the polar trough and developing low over
Southcentral will promote outflow winds late Friday into the
morning hours on Saturday. The usual locations from Seward to
Valdez will be the most susceptible with gusts anywhere from 25 to
35 mph.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (through Saturday morning)...

A band of snow will continue for interior Bristol Bay this
evening, extending up into the Lower Kuskokwim Valley. Further
snowfall amounts should be an inch or less. Colder air filters
back across the southwest Mainland behind the front bringing low
temperatures in the single digits in most areas. Attention quickly
turns to a developing quick-hitting compact low riding along the
ice edge on Thursday which will move toward the Yukon Delta. The
front will spread snow over the Kuskokwim Delta during the morning
hours. As the front passes, winds will turn out of the west and
become gusty as the temperature drops. The combination of falling
snow and winds will create the potential for a short period of
blizzard conditions. The front will move inland quickly Thursday
afternoon and evening bringing the blowing snow threat with it,
and could extend into Aniak in the late evening hours. As the
front progresses eastward snow is possible across the Lower
Kuskokwim Valley through Bristol Bay, mainly along the Alaska
Range. The next active weather will be front from the Bering Sea
bringing southerly winds to the area on Saturday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (through Saturday
morning)...

Snow showers continue over the central and eastern Bering Sea. A
developing hybrid/polar low will develop quickly in the vicinity
of Saint Matthew Island early Thursday morning. Gale-force winds
will be associated with the front. Cold air filtering down from
the ice pack and gusty winds will create the opportunity for heavy
freezing spray in a narrow corridor closer to the ice edge, with
lighter freezing spray elsewhere. Early Friday, a north Pacific
low and front will bring widespread southerly winds to the Bering
with storm-force winds impacting the western Aleutians and Bering
on Friday.

&&

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

A ridge will build into Southcentral Saturday bringing quieter
weather through Sunday before another Bering Sea front approaches
Sunday into Monday. This creates another problem with possible
precipitation for Southcentral heading into the week due to the
development of a possible surface low in the Gulf. Out west,
northern parts of Bristol Bay into the Kuskokwim Delta region
could get clipped by a Bering low pressure's warm-front Friday
into Saturday. Light precipitation chances would be associated
with the aforementioned front. The cold-front of this Bering low
will track into the Southwest coast by Saturday night into Sunday
morning. Accompanying this front will be gale-force winds with
possible storm-force gusts, especially for the western Aleutians.
As the front progresses eastward throughout the central and
eastern Bering, winds will weaken mostly to low-end gales to high-
end small craft through Sunday morning. Southwest looks to become
unsettled late Saturday night into Monday as the front crosses
southern mainland. There are still a few timing differences
regarding the progression of the front through Southwest during
the week. However, the progressive pattern looks to continue with
no real sustained breaks in activity.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 125.
		 Winter Storm Watch 155.
		 Winter Weather Advisory 171.
MARINE...Storm Warning 734
		 Gale Warning 716 730-733 738 750-753 757 760-762
					  351 352 412.
		 Heavy Freezing Spray Warning 760-762 764 767 412 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CJ
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...NS