Winter Storm Warning 4, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
454 PM AKST Sun Feb 20 2022

.SYNOPSIS...
Northern Alaska is now entering a warmer and active weather
pattern. Warm southwest flow is now pushing a mix of moderate to
heavy snow, freezing rain and sleet over the West Coast and
Western Interior today into tonight, with snow and warmer
conditions spreading to the Eastern Interior and North Slope on
Mon and Tue. Wed will see another round of warm, wet and windy
conditions along the West Coast and Western Interior while the
North Slope and Eastern Interior clear out and remain much warmer
than normal.

Very cold winds chills over the North Slope will become less
severe Mon as temperatures rise.

Blizzard and near blizzard conditions over the Seward Peninsula
will spread north tonight. Mixed precipitation, brief blizzard
conditions, light ice accumulation, and 4-6 inches area expected over
the area from the Seward Pen south and over the Western Interior.
Snow will spread north and east over NW Alaska and the Central
Interior on Mon, with light snow over the North Slope and Interior
on Mon night and Tue. Expect 4-6 inches of snow over the West
Coast and Western Interior by Mon night, with 3-6 inches of snow
over the Eastern Interior Mon night and Tue with the heaviest
amounts over the White Mountains and Denali areas. Just light snow
over the North Slope.

Expect strong south winds and blowing snow through Brooks Range
passes through Mon.

Strong south winds possible through Alaska Range passes Mon night.

Could see significant Winter Weather with mixed preciptiation
along the West Coast and Western Interior Wed.

Aloft...
The long wave pattern consists of a strong ridge over
the Eastern Pacific and Western N America with a deep trough over
the Bering and NW Pacific. A strong short wave now over Bristol
Bay will move north over the West Coast and Western Interior
tonight and to the North Slope and Central Interior on Mon, and
along the ALCAN Border Mon night. A strong southwest flow of warm
and moist air follows this trough NE across Alaska. A series of
short wave troughs will continue to move north over Alaska in
this pattern through next weekend. This will cause Northern
Alaska to be much warmer and wetter than normal from Mon through
next weekend, with the Eastern Interior having periods of drier
chinook conditions.

Surface...
Strong 1045 mb high pressure north of the Arctic Coast of Alaska
will move east over the Beaufort Sea tonight build south over NW
Canada tonight and Mon, then weaken on Tue. This will cause east
winds 15-25 mph along the Arctic Coast tonight and continue
through Mon. This will also cause east winds at Delta Junction and
Eagle to develop tonight and continue into Mon night. Also expect
this to cause southerly gap flow winds through Alaska Range
passes to increase to 30 mph tonight and to 50 mph on Mon night.
Since flow aloft remains SW over the Alaska Range, do not expect
warning level winds at this time.

A strong low in the southwest Bering Sea will move to 100 NM west
of St Matthew Is as a 982 mb low by 3pm Mon, and to 300 NM
northwest of Cape Lisburne as a 993 mb low by 3pm Tue. An occluded
front that stretches from the low to Bristol Bay, with a warm
from St Matthew Is to Anvik. The occluded front will move to the
Bering Strait to McGrath by 3am Mon with a warm front from McGrath
south, then to Point Lay to Ambler to Mcgrath by 3pm Mon, to
Deadhorse to a 1007 mb low near McGrath by 3am Tue, and to north
of the Arctic Coast to Inuvik to a 2020 mb low near Delta Junction
by 3pm Tue. Expect snow ahead of this front with mixed snow and
freezing rain along and south of the front this evening, with
precipitation changing to all snow late tonight as the front
occludes. Areas of freezing rain will be from the Seward Pen to
McGrath south tonight and leave a light glaze of ice. A moderately
heavy area of snow will moves NE across Interior AK Mon night and
Tue near the frontal Wave low. May need to issue Snow advisories
for the Central Interior Mon night into Tue tracking along this
low.

Expect Blizzard conditions along the Seward Pen to spread north
to Point Hope tonight and continue into Mon, then diminish south
of the Brooks Range Mon PM.

Another strong storm will move north over the Bering Sea on Wed
bringing snow and a chance of freezing rain to the West Coast and
Western Interior on Wed. These may require more warnings.

&&

.DISCUSSION...
At 12Z, models initialize well aloft. Models show similar
solutions aloft through 3am Tue, then the GFS is slower than
other models in the eastward progression of short waves over the
Interior and in the following ridge building over Northern AK on
Tue and Wed. The ECMWF, NAM and Canadian models all maintain
similar solutions aloft into Wed. Favor a blend of the NAM/ECMWF
and Canadian aloft through Wed.

Beyond Wed models show similar long wave patterns through next
weekend, with a broad ridge over the Eastern Pacific and Western
N America with a deep trough over the Bering and NW Pacific with
a series of short wave troughs moving north over Alaska in the
pattern. This will cause Northern Alaska to be much warmer and
wetter than normal from the second half of the week, with the
Eastern Interior having periods of drier chinook conditions.

850 mb temperatures rise above freezing over SW Alaska this
afternoon, and spread to the Seward Peninsula to McGrath and
Western Alaska Range Areas by midnight. Expect mixed precip south
along and south of this freezing long this evening into early Mon.
Above freezing temps at 850 mb return to SW Alaska Tue night, and
across most of the Interior south of the Yukon River and the West
Coast south of Kotzebue on Wed. This will bring the possibility
of mixed precip to those areas on Wed. We favor the ECMWF, NAM and
Canadian for 850 mb Temps since the GFS is out of phase from Tue
on.

For precipitation models show similar pattern through 3am Tue,
then differ some on timing. Will use a blend of the GFS/NAM and
ECMWF precip for location and amounts through 3am Tue, then a
blend of the ECMWF and NAM for Tue into Wed.

At the surface at 18Z, models verify well on features but all are
4-6 mb too weak on the high north of the Arctic Coast. Models show
similar surface patterns through 3pm Tue, then prefer the NAM and
ECMWF at surface for Tue and Wed as they maintain a deeper and
slower moving low over NW AK than the GFS does. Will adjust up
winds along the Arctic coast 3-5 kt today and today to account
for the stronger high to the north than what models indicate

Bottom line for models is will use a blend of models through 3am
Tue for temps, precip, clouds, then use a blend of the NAM/ECMWF
and Canadian for temps precip and clouds for Tue into Wed.
For surface fields and winds will use a blend of the NAM/ECMWF
and Canadian but bump up winds 3-5kt above models along the
Arctic Coast through tonight.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory for AKZ201-AKZ202-AKZ203-AKZ204.

Winter Storm Warning for AKZ211.

Blizzard Warning for AKZ207-AKZ208-AKZ209-AKZ213.

Winter Weather Advisory for AKZ206-AKZ210-AKZ212-AKZ214-AKZ215-
AKZ216-AKZ217-AKZ219-AKZ227.

Small Craft Advisory for PKZ235-PKZ240-PKZ245.

Gale Warning for PKZ200-PKZ210-PKZ215-PKZ220-PKZ225.
&&

JB FEB 22