Gale Warning 174, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
539 AM AKST Mon Feb 14 2022

.ANALYSIS AND UPPER LEVELS...

A well developed low center over the north Pacific is continuing
to drift north. Its occluded front is over the Bering with gales
reported through scatterometer data. Lower visibility with snow is
was reported at St Paul Island and had changed over the mixed
precipitation and rain around 3AM. A rich plume of subtropical
moisture is reaching the AKPen where the triple point associated
with this low is located. Temperatures overnight hovered near 40
degrees and rain from Unalaska to Sand Point. Snow is beginning
to fall along the coastal locations of southwest Alaska and
Bristol Bay as moisture spreads out and becomes available
downstream.

Looking east, drier conditions at the surface with widespread
cloud cover riding over top an upper ridge axis centered near
Kodiak Island and the western Gulf. Low stratus and fog is
situated over the Kenai, Cook Inlet, and north into the Susitna
Valley. But, higher clouds are beginning to filter into
Southcentral. The blocked high pressure over the Eastern Pacific
will continue to send waves of instability along this ridge axis
in the short term.

&&

.MODEL DISCUSSION...

General model agreement in the short term is good with the
placement and strength of major key features being the blocking
ridge over the eastern Pacific, the mature low approaching the
Aleutians, a short wave over the Kuskokwim Delta late Monday
phased with a weak embedded wave stretching along the ridge axis
over southcentral.

Subtle differences continue from run to run with the northern
extent of warm air. This will affect the timing of the
transitioning of PType over the next few hours for St Paul and the
progression of the downstream with the surface to midlevel
features at play for the southwest Alaska. An added layer of
complication is the cold air having been in place with the
northerly winds at the surface across the entire southwest, the
warm air overriding and speed at which this warm, moist air chews
away at that cold air further inland. The Bristol Bay interior
could see a wintry mix, including a brief period of freezing rain
possible overnight into Tuesday morning.

A fast developing north Pacific low will beam north and as it
approaches the eastern Bering late Tuesday night, model agreement
is degraded enough to have more variation in QPF and the
orientation and timing of the main moisture band stretching from
southwest Alaska to southcentral. NAM is currently lagging behind
and the EC ahead of the GFS. Areas along Cook Inlet are included
in some variation of the models for warm air and the extent north
along the Inlet Wednesday. NAM is also being more aggressive with
the warmer air. Models disagree on the gradual transition of cool
air filtering behind sometime Thursday into Friday. To the west
during this time frame, a couplet of lows linger over the
Aleutians, blocked by the persistent eastern Pacific ridge.

&&

.AVIATION...
PANC...IFR/LIFR conditions with the low stratus deck may linger
through the late morning. Otherwise, expect MVFR conditions in the
afternoon. Snow chances will increase throughout the day however,
and return to lowered ceilings and visibility is possible with
snowfall Monday evening through Tuesday morning. Southeasterly
winds increase through Turnagain arm Monday night and may bend
northward into west Anchorage Tuesday morning. A southerly wind
would produce winds of about 10 kts with slightly higher gusts and
should diminish by Tuesday afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Wednesday Night)...

A VERY active weather pattern continues for Southcentral right
through the short-term period and beyond as a series of at least 2
storm systems moves across the area through Wednesday night, with
additional storms following those right through into the weekend.

Starting with today, the next in our series of snow-producing
storms is already beginning to encroach on the area in the form of
thickening cloud cover from southwest to northeast this morning.
Precipitation has already begun over the southern part of Kodiak
Island, and will spread into Kodiak by sunrise. Temperatures are
already above freezing in Kodiak so it shouldn't take long for
the sun to warm things enough to change the snow over to rain
later on this morning. Meanwhile, snow will spread into the
southern Kenai Peninsula late this morning, moving into Anchorage
during the afternoon, then into the Valley by early this evening.
The snow will continue into the overnight hours, ending from
southwest to northeast by midnight for the southern Kenai, and by
the start of the Tuesday morning commute in Anchorage. Snow will
linger much longer into Tuesday in the Valley, possibly not
stopping until Tuesday afternoon.

The break in the weather for the day Tuesday will be very brief. A
second stronger storm system may cause snow to restart over the
southern Kenai Peninsula as early as Tuesday evening and certainly
by midnight, spreading north and east into Anchorage just in time
for the Wednesday morning commute. Due to this event both being
stronger and having warmer air to work with, the rain/snow line is
expected to intrude much further north up the Kenai Peninsula with
the Wednesday event as compared to tonight's event. There remains
considerable uncertainty as to whether or not it gets into
Anchorage, along with any Knik River Valley wind attempting to
change precipitation over to rain for portions of the Valley.
While there is a fair amount more moisture with this second round,
the warmer temperatures may result in less snow for most areas,
since there will both be better potential to mix with rain and
what snow does fall will be wet and heavy, which is the slow-to-
accumulate type of snow. The precipitation will end from southwest
to northeast Wednesday afternoon and evening, however, favorable
flow will allow the snow to persist once again in the Valley and
along the mountains into Wednesday night. Somewhat cooler air
filling in behind this event will also favor continued light snow
well into Wednesday afternoon and evening. The forecast for the
Wednesday event is still being refined so stay tuned for further
updates.

Two rounds of snow are enough, right? Wrong. While there is
significant uncertainty as to the timing, all indications are that
sometime either during the day Thursday or Thursday night, yet
another round of wintry weather moves in. This third round of snow
does look to be a colder solution, which would of course favor
most areas staying all-snow, but with all the aforementioned
uncertainty, it wouldn't be prudent to speculate on details with
this round of precipitation yet. Stay tuned!

&&

.CLIMATE...

So far through yesterday, February has already had 15.0 inches of
snow measured in Anchorage. If the month ended today, this would
be the 28th snowiest February on record, already in the upper half
of snowiest Februaries on record. With a series of at least 4
storm systems expected to impact the region through this weekend,
it appears very likely that we will move into the top 10 snowiest
Februaries, when the monthly total surpasses 20.8 inches of snow.

Through February 13th, this is the 7th snowiest start to February
on record.

Top 10 Snowiest Februaries on Record
------------------------------------
1) 52.1 inches - 1996
2) 48.5 inches - 1955
3) 33.1 inches - 1956
4) 27.8 inches - 2012
5) 26.1 inches - 1968
6) 25.3 inches - 2018
7) 23.0 inches - 1990
8) 22.8 inches - 1974
9) 21.4 inches - 2001
10) 20.8 inches- 1978
28) 15.0 inches- 2022

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3 - Today
through Thursday)...

The front extending from a western Aleutian low is currently
pushing eastward into Southwest. As the front passes and the
surface winds shift from northeasterly to southerly, there will
be a quick transition from snow to rain across northern and inland
Bristol Bay late tonight into Tuesday morning. A brief period of
freezing rain may be possible for these areas during this time.

Northeasterly winds along the Kuskokwim Delta Coast are increasing
as the front approaches. As a result, snow and blowing snow are
possible for the Kuskokwim Delta Coast this morning and lasting
into the evening. Please see the associated Winter Weather
Advisory for more details. A front extending from a Bering low
will push across the Alaska Peninsula and into Southwest late
Tuesday into Wednesday. Precipitation with this feature is
expected to stay as rain along the Alaska Peninsula, however the
exact track the low ends up taking will dictate the type of
precipitation for a majority of Southwest.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3 -
Today through Thursday)...

A strong North Pacific low will continue its track northwestward
across the western Aleutians through Tuesday afternoon. The front
extending from the low will continue to push northeastward towards
Southwest. Storm force winds with the low will persist across the
western Bering through Monday night. Hereafter, winds will
diminish to gales across parts of the northwestern Bering and will
last into Wednesday. Widespread precipitation across the
northwestern Bering and western Aleutians will diminish early
Wednesday morning as the low tracks father west away from the
forecast area.

Two more systems are going to impact the Bering Sea and Aleutians
through Thursday. One of the lows will track from the North
Pacific over Unalaska on Tuesday night and then will enter the
eastern Bering on Wednesday morning. The front with this low will
push over the eastern Aleutians on Tuesday, and rain is expected
to be the precipitation type associated with this feature. Another
North Pacific low will move over the western Aleutians Wednesday
morning and enter the southern Bering Thursday. There is still
significant model discrepancy with the track of this low, so the
details concerning this system will continue to be refined through
the subsequent forecast packages.

&&

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

Gulf of Alaska:

A front pushes into the Gulf Wednesday morning, bringing
widespread southerly small craft winds, 10 to 15 ft seas, and rain.
Winds largely diminish below small crafts, waves decrease below
10 ft, and rain peters off around Thursday morning. Uncertainty
increases Thursday evening regarding the track and strength of an
incoming North Pacific low and its front. Winds will likely
increase to small crafts between Thursday evening and Friday as
the front tracks through the Gulf. However, the extent and
duration of small craft winds, as well as the potential for gales,
is difficult to determine at this time. Precipitation associated
with this front will likely fall as rain or rain/snow mix. By late
Friday evening, the low looks to move over the Northern Gulf,
bringing the potential for gusty, westerly gap winds and freezing
spray. Rain and rain/snow mix will transition to snow showers.

Bering Sea/Aleutians:

A busy pattern persists for the Bering and Aleutians through
Friday. On Wednesday, small craft winds and seas approaching 20 ft
are expected near the Eastern Aleutians as a surface low moves
from the North Pacific into Bristol Bay. Further west, a strong
North Pacific low tracks along the Aleutians Wednesday morning
through Friday. Rain or rain/snow mix falling ahead of the low
will transition into snow showers behind it. The low weakens
quickly, so while widespread small crafts are expected, gales will
be limited mostly to the Northern Bering and south of the
Aleutians. Seas 15 to 25 ft are expected near the low, with seas 8
to 15 ft elsewhere. There is some uncertainty as this low
interacts with a compact low moving across the Eastern Aleutians
and into Southwest Alaska on Thursday. However, both systems look
to remain fairly weak as they interact, with winds remaining small
crafts or lower. On Friday, yet another low pushes its front west
towards the Central Aleutians, bringing a broad swath of gales
and rain.

&&

.Long Term Discussion (Days 4 through 7: Thursday through
Sunday)...

An occluding North Pacific low tracks along the Aleutians from
Thursday through Friday evening. A triple point low forms near the
Eastern Aleutians Thursday morning, introducing uncertainty as
these two features interact. The EC suggests that the triple point
low will be absorbed into the occluding low, while the GFS and
GEM suggest that the two surface lows will rotate around each
other. How these lows interact has implications for winds and
precipitation. For example, the GFS brings the compact low
further north into the Kuskokwim Delta and Bristol Bay on
Thursday, suggesting greater snow amounts in those areas as
compared to the GEM. As the GFS brings the low further north, it
brings an increased potential for rain along Southern Bristol Bay
due to greater warm air intrusion inland. In contrast, the GEM
brings the compact low straight towards the Prince William Sound,
suggesting greater snow amounts along the North Gulf coast from
Thursday afternoon through Friday evening as compared to the GFS.
With winds, the GEM's stronger North Gulf low suggests that gap
winds will approach storm force early Saturday morning, as
compared to winds below small crafts with the GFS and EC.
Overall, details remain uncertain at this time for the front
tracking across southern Alaska from Thursday morning through
Friday, as well as for the various surface lows.

As this strong system moves across southern Alaska Thursday
through Friday, a ridge builds behind it. This heralds a brief
return to calmer weather and colder conditions through most of
Saturday. However, unsettled conditions resume as a strong low
near the Western Aleutians pushes its front across the Bering. The
front reaches Southwest Alaska late Saturday night into Sunday
morning. Confidence decreases at this point due to poor model
agreement. While details are uncertain, the position of the upper
level longwave trough over Alaska suggests that unsettled weather
is likely.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory: 155.
MARINE...Storm: 411;
		 Gales: 175 - 178, 185, 412;
		 Heavy Freezing Spray: 185, 411, 412.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...VR
SOUTHCENTRAL ALASKA/CLIMATE...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AF
MARINE/LONG TERM...KC

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