Gale Warning 227, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
550 PM AKDT Tue Mar 29 2022

.ANALYSIS AND UPPER LEVELS...

The upper levels continue to show an amplified pattern with the
300mb jet traveling from southern Kamchatka and dipping well
south of the Aleutians. The jet will then travel northward
towards the Eastern Aleutians and AKPen before moving southward
towards the Pacific Northwest. A 500mb low is centered near Attu
Island with a ridge across the AKPen and eastern Bering and a
trough extending across the Gulf. At the surface an occluded front
is moving across the Eastern Aleutians and Bering with gales near
the front as well as a swath of rain with some snow mixed in near
Cold Bay. Across the eastern Bering, Pribilofs, and AKPen low
stratus and fog have been observed. The weakening surface low and
trough near Kodiak Island continues to produce a few showers
across Bristol Bay, with a rain and snow mix as temperatures are
in the mid 30s. Clouds persist across the Kuskokwim Valley and
Delta areas with mainly dry conditions and temperatures in the
30s. Across the Gulf, onshore flow from the weakening trough
continues to produce rain and snow showers mainly near coastal
locations. Elsewhere across Southcentral Alaska, a mix of clouds
and sun are seen on satellite and observations with temperatures
in the 30s and 40s.

&&

.MODEL DISCUSSION...

Models are in good agreement through Thursday. However, by
Thursday night and Friday there are some significant differences
between the models on the timing of the front lifting across the
northern Gulf as well as the low moving near the southern tip of
Kodiak Island and into the AKPen. The NAM has a much more distinct
front from other models while the GFS continues to move the low
farther southwest than the other models. These differences will
impact the timing of the gale force winds across the marine zones
as well as the timing of heavier precipitation along the coast. We
decided to use a blend of the GEM and GFS through 12z Friday, but
did not do any updates after this time due to model
uncertainties.

&&

.AVIATION...
PANC...VFR conditions are expected through tonight with light
winds. As the clearing skies continue overnight fog and stratus
are likely to develop over the Knik Arm. It is possible that we
will see low stratus at the terminal by tomorrow morning as well
as patchy fog, but there is forecast uncertainty. Fog has been
added to the TAF.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Tonight through Thursday
night)...

Patches of blue sky have made an appearance today across
Southcentral and will continue to see clearing into Wednesday
night. There remains some lingering moisture along the north Gulf
Coast today, as remnant low pressure lingers along the northern
Gulf. Rain showers will likely continue into early this evening
before tapering off. The next front reaches Kodiak Wednesday
afternoon and pushes northwards across the Gulf through Thursday
night. The associated low approaches out of the North Pacific,
making it as far north as the southern Gulf by Thursday night
before changing trajectory and moving westward. This is likely due
to the combination Arctic high pressure situated over
northwestern Alaska and the upper level low over Canada keeping
the North Pacific low from traveling any further. Most of the
precipitation will be confined to the coastal regions as the low
takes the westward track and the front weakens as it pushes the
northern Gulf. There is still quite a bit of model inconsistency
with this next system, particularly with winds across the Gulf, as
well as across Kodiak Island and southern Kenai Peninsula, and
precipitation amounts for the coastal regions. Daytime
temperatures are expected to be in the low 40's with overnight
temperatures dropping below freezing. Thus, precipitation should
fall as rain during the day and then transition to a rain/snow mix
or all snow during the overnight hours.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 to 3: Tonight
through Friday)...

A mild and quiet start is expected across the area this evening,
with temperatures over interior valleys rising up to 40 degrees
or so where stratus in place earlier has cleared up. Even with
snow cover is partly still in place, this clearing has allowed
enough daytime heating for modest instability to develop over
Bristol Bay in and around King Salmon. This has aided in the
development of scattered convective rain showers in the area, but
this activity should rapidly subside as the sun sets and
temperatures cool.

For Wednesday, a frontal system moving out of the eastern Bering
will spread a band of precipitation onshore into parts of the Y-K
Delta and Bristol Bay. A deep fetch of strengthening southeast
flow and warm advection will increase low level temperatures
ahead of the frontal axis, resulting in mainly a rain-snow mix
transitioning to mostly rain by the afternoon as valley
temperatures again rise into the upper 30s to low 40s. Central
portions of Bristol Bay and the eastern Y-K Delta should stay
mostly dry throughout the day due to downslope flow off of the
Alaska Range and Kuskokwim Mountains.

By early Thursday, the weakening front will stall out as it runs
into a strengthening ridge axis developing over the Alaska
interior. A new system will begin to work around this ridge and
approach the southern Gulf and effectively pull the southern
portion of the front back west as flow aloft becomes more
easterly. A band of more moderate precipitation will develop over
Bristol Bay and move west along this axis throughout the day on
Thursday, with temperatures perhaps initially cold enough for a
couple inches of wet and slushy snow for places including Pilot
Point and Dillingham. Similar to Wednesday, a transition over to
rain is expected with afternoon heating. Forecast uncertainty
picks up heading into Friday, with models diverging on the
handling of the Gulf low as it attempts to retrograde west into
the Alaska Peninsula. However, anticipate this system to remain
low impact, with most of continued periods of easterly wind and
rain/snow confined mostly to the northern Alaska Peninsula.

&&

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

A front now approaching Unalaska will continue to advance north
and east tonight into early Wednesday, with southeast winds and
mainly rain moving ahead of the front as is progresses from the
Eastern Aleutians into the southern Alaska Peninsula. Farther
north, colder temperatures will support snow with the frontal
passage across the Pribilofs. Around 2 inches of new snow
accumulation remains expected ahead of the front through Wednesday
morning, with gusty easterly winds also leading to periods of
blowing snow and visibility reductions. A broad upper low will
move into the Bering behind the front, allowing quiet conditions
to return to most of the region through Friday. Occasional rain
and snow showers will move across the Aleutian Chain with steady
westerly winds on Thursday and Friday.

&&.MARINE (Days 3 through 5 - Friday through Sunday)...

Gulf of Alaska - A weakening low moves across Kodiak Island and
the Alaska Peninsula as its front extends to a second low in the
eastern Gulf through Sunday. Forecast confidence is mixed, due to
the tracks of the lows. High end gales wrap the low from the
northeast through Cook Inlet, Kamishak Bay and the Barren
Islands, and from the southern Gulf to east of Kodiak Island,
diminishing Saturday. Gusty easterly winds continue over the Gulf
through Sunday. Seas to 18 feet are expected over the Gulf and
Shelikof Strait for Friday, and to 13 feet over Kamishak Bay,
subsiding.

Bering - A western Bering low moves to the Central Bering, and a
Bristol Bay low moves to near Nunivak Island Sunday. A front
extends across the Bering between the two lows. A North Pacific
low deepens as it moves east to the south of the Aleutians
through Sunday. Forecast confidence is mixed with the timing of
the lows. High end northeasterly gales over Bristol Bay diminish
Saturday. Seas less than 10 feet. Winds increase to high end gales
over the Aleutians and southern Bering on Sunday. Seas building
to 18 feet along the Pacific side of the Aleutians by Sunday.

&&

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

Looking ahead in the extended forecast, the latest operational
model runs are in decent agreement with the evolution and
progression of the synoptic scale features, but begin to diverge
in the specific details towards the end of the period. The pattern
remains amplified with a broad trough over the Bering
Sea/Aleutian Islands, extending eastward across the Gulf and over
Southcentral Alaska. A surface low near the Alaska Peninsula
dissipates on Saturday, while the associated front stalls out
along the north Gulf Coast. Meanwhile, a couple of stronger
systems tracks along the Aleutians into the Gulf during the
weekend into early next week. Even though there is a good amount
of uncertainty with these systems, most of the precipitation will
be concentrated through the Panhandle and up into the southern
coasts. Much of the mainland should be relatively dry during the
period, with the exception for potential snow in the mountains and
colder inland areas. Out west, an active storm pattern associated
with the aforementioned broad trough will maintain showery
conditions and gusty winds for much across the Bering and
Aleutians into early next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 130 131 160 178 180 185 411 412.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...KM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
MARINE/LONG TERM...KZ/MF