Gale Warning 160, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
646 PM AKST Tue Feb 8 2022

.ANALYSIS AND UPPER LEVELS...

A strong upper level low remains anchored in place across
Southwest Alaska with the center near Hooper Bay. This upper level
low extends a trough southward through the Bering Sea spilling
Arctic air southward even south of the Aleutian Island Chain.
Saint Paul Island actually dipped below zero this morning (-1
degree to be exact.) The last time Saint Paul dipped below zero
was on February 19, 2017...nearly 5 years ago! Widespread teens
to single numbers below zero were observed across much of
Southwest Alaska this morning with Adak even down into the low 20s
due to the widespread Arctic air. On visible satellite imagery,
you can see cloud streets coming off the ice edge as the Arctic
air moves over the relatively warm water of the Bering. This
creates an unstable atmospheric profile resulting in occasional
snow showers. Further east, an upper level shortwave trough is
seen on water vapor imagery moving northward through Southcentral.
This feature is responsible for the snow seen across the area
today. Very dry air is also seen on water vapor imagery around
Kodiak Island behind this upper level shortwave trough. Another
low pressure system is seen on satellite imagery currently south
of Dutch Harbor over the North Pacific which will be the next
system to impact Southcentral tonight through Wednesday.

&&

.MODEL DISCUSSION...

Models remain in fairly good agreement on the synoptic scale
features out through Day 3. Models remain in good agreement on the
system that is expected to track northward from the North Pacific
and into the Gulf tonight through Wednesday. Therefore, minimal
changes were made to the forecast this package. The main
differences arise with the next system that will be moving
northward towards the Aleutian Islands and the Bering Sea
Wednesday evening through Thursday. Models are continuing to
struggle with if there will be one concentric low center or two
different low centers with one going towards Adak and the other
one towards the Shumagin Islands. Therefore, the placement of
these lows and exact track will factor into the sensible weather
for the Aleutian Island Chain.

&&

.AVIATION...

PANC...MVFR conditions this afternoon are expected to lift to VFR
conditions this evening through around midnight. Ceilings will
come down again around midnight with light snow moving back over
the terminal as the next system approaches with MVFR conditions
expected, though, potentially IFR conditions are possible.
Conditions should begin to improve towards late Wednesday
afternoon/early evening to VFR conditions. Gusty southerly winds
remain expected at the terminal this afternoon for a brief time
before diminishing this evening. Winds will remain light and
variable overnight before increasing out of the southwest
Wednesday afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Friday night)...

More snow is expected as another low makes its way into
Southcentral this evening. Much of the area will see some snow
between now and Wednesday, with the highest amounts expected in
the Eastern Prince William Sound. Snow will first arrive in
Kodiak early Tuesday evening, then quickly make its way into the
southern mainland late Tuesday evening with the support of a
robust jet aloft. Heavy snowfall rates and blowing snow may reduce
visibilities, especially for the Eastern Kenai Peninsula and
Eastern Prince William Sound. The most favored locations are
Portage Valley and Thompson Pass, where Winter Weather Advisories
have been issued. Nearer the coast, locations along the Eastern
Prince William Sound such as Cordova will likely see rain or a
rain/snow mix as temperatures rise above freezing.

Precipitation will slowly diminish through Wednesday. Additional
snow is possible Wednesday evening and into Thursday as an upper
level low pivots from Southwest Alaska towards Southcentral. Weak
shortwaves moving around the upper level low will bring
relatively light, localized, and short-lived periods of snow. The
bigger story is cold air wrapping around the backside of the low
as it tracks across Prince William Sound and into the interior.
Temperatures will decrease Wednesday night into Thursday, with
lows dropping into the single digits and teens. For mariners, this
cold air advection will bring the threat of freezing spray and
heavy freezing spray.

Another low, supported by a strong jet aloft, makes its way
towards Southcentral Thursday afternoon. For now, precipitation looks
to remain mostly near the coast, with snow as the primary
precipitation type. However, the influx of warmer air with the
low may bring the potential for snow to mix with rain. The bulk of
precipitation will shift towards Southeast Alaska early Friday
morning, limiting overall precipitation amounts.

&&

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

A stout, upper-level polar low remains entrenched over the
northern Bering with a very cold, arctic airmass extending from
eastern Russia to Southwest Alaska. A surface ridge over Southwest
will keep conditions mainly clear with temperatures well below
normal through Wednesday morning. A few areas of fog are possible
overnight, especially across the Kuskokwim Delta. Scattered snow
showers are also possible along the immediate coast of the
Kuskokwim Delta as a westerly wind off the ice sheet wraps low-
level moisture around a low near Norton Sound.

A shortwave trough will move east from the Pribilofs Wednesday,
spinning up a compact surface low southwest of Cape Newenham. This
low will quickly gain strength as it tracks toward Bristol Bay. A
quick shot of snow, generally one to two inches, is likely across
the Bristol Bay region late Wednesday. Some blowing snow is also
possible, especially along the coast, as winds increase ahead of
the low. This feature moves east and weakens quickly Thursday as a
transient ridge builds in. The next system then looks to move from
the north Pacific to the AKPen for Friday, with snow likely
developing once again across Bristol Bay.

&&

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

Northerly flow due to a strong ridge of high pressure over Siberia
and a surface low near Norton Sound is continuing to produce
numerous cloud streets and snow showers across much of the Bering.
The arctic airmass, combined with the wind, is also producing
expansive areas of heavy freezing spray and even some extreme
freezing spray along the ice edge in the northern and eastern
Bering.

Colder air will move across the AKPen later tonight and into
Wednesday morning as a upper-level wave and surface low move from
the northern Pacific. Northerly winds will increase with storm-
force gusts likely out of bays and passes along the southern coast
of the AKPen. These winds will diminish through Wednesday as the
low moves northeast and a ridge advances toward the AKPen from the
south.

Farther west, a complex low with multiple centers of circulation
will move from the North Pacific to the Central Aleutians for
Thursday. The first of the centers will lift a trough across Adak
and Atka Thursday morning with snow and gusty easterly winds. A
second, stronger system then moves toward Unalaska by late
Thursday morning with a likely mix of snow and rain. Conditions
remain unsettled across the Bering through Friday as the low
lifts north and stalls.

&&

.Marine (Days 3 through 5: Friday through Sunday)...

Gulf of Alaska:

Cyclonic flow will influence the Gulf. A frontal system will move
into the region Friday bringing widespread gale force winds. The
low will track inland and weaken, expect the winds to slack off
Saturday. Then another low will move into the Gulf on Sunday but
quickly move inland over SE Alaska.

Bering Sea/Aleutians:

Uncertainty persists with the strength and track of an incoming
North Pacific low. Expect fast moving systems. A North Pacific
low approaches the region Saturday evening. Overall, waves will be
mostly 8-15 ft, with seas peaking around 20 ft where gales are
expected. As winds stay mostly northeasterly through the period,
cold air advection and freezing spray will likely continue to be
concerns.

&&

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

Models are continuing to indicate an active and wet period for the
North Pacific with the persistence of a longwave trough over the
Bering and the Northwest Pacific. Models are showing back to back
lows moving out of the Pacific. By 96 hrs, there is a significant
amount of models divergence which will impact the track and the
timing of the precipitation. At 500 mb there is an area of
positive height anomalies over the Gulf Of Alaska and SE Alaska
from Day 4 to Day 7. Also there is a broad area of negative height
anomalies over the Bering, SW Alaska and NW Pacific on Day 4.
However, the intensity of the anomalies over the Bering wanes but
the anomalies over the NW Pacific get stronger. Expect the NW
Pacific to be an area of cyclogenesis this entire forecast period.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Avalanche Warning: 131.
 		 Winter Weather Advisory: 125 131.
MARINE...Storm Warning: 119 120.
Gale Warning: 125 129-132 138 139 141 150 160 165 185-352.
Heavy Freezing Spray Warning: 130-132 137-139 141-155 165 179 185
							  411 412 414.

&&

SYNOPSIS AND MODEL DISCUSSION...MV
SOUTHCENTRAL ALASKA...KC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TM
MARINE/LONG TERM...PJS