Gale Warning 344, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
432 PM AKDT Tue Apr 19 2022

.ANALYSIS AND UPPER LEVELS...
The upper level high at 500 mb over mainland Alaska has made a
subtle transition and is now in a Rex Block pattern as opposed to
the omega block from last week. This is due to the upper high over
the Interior of the state getting closed off and sitting just north
of the weak upper level low that developed along the north Gulf
of Alaska coast. This blocking pattern is keeping mainland Alaska
mostly sunny today. Easterly flow can be found over the Gulf of
ALaska which is keeping some clouds over Kodiak.

The surface low that is just south of the Alaska Peninsula is
weakening, but still has some punch in the northwesterly winds
over the Eastern Aleutians. Nikolski has had consistently strong
northwesterly winds in the 55-60 mph range this afternoon. Cold
air can also be seen in the cold air cumulus streaming across the
southwest Bering Sea and through the central Aleutians. Southwest
mainland Alaska and the eastern Bering Sea are in the warm sector
and this is bringing afternoon temperatures well into the 40s for
most of Southwest mainland Alaska.

&&

.MODEL DISCUSSION...
Another boring model discussion day. Models remain in good
agreement through the remainder of the week over southern Alaska
including through the Aleutians. A meaningful difference appears
early next week with the way a low in the Bering Sea develops and
moves eastward and that will have an impact on the forecast for
the Bering at that time, but until then very good model agreement.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

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

Quiet conditions will continue Thursday. An upper low is currently
centered over Southcentral, however mostly sunny skies are
observed across much of the region in a weak synoptic offshore
flow and large dew point spreads indicate an absence of any
moisture. Settled weather will persist into Thursday, with a weak
Turnagain wind developing in the afternoon ahead of a front. This
front will enter the western Gulf by Thursday evening as its
associated low begins to occlude in the North Pacific. Steady rain
is expected over Kodiak Friday morning, with light snow expected
along Prince William Sound. Precipitation will change to rain and
continue through the day. Gusty southeasterly Turnagain winds will
likewise continue, however are not expected to bend into Anchorage
with a relatively stronger down-Inlet pressure gradient.

&&

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

An upper-level low over Southcentral will track westward
Wednesday and cause onshore flow to develop. This, with the help
of short-waves moving through the region, will result in chances
of rain over the Bristol Bay area in the evening and help to usher
clouds back over the Southwest. However, interior locations will
likely stay mostly clear. As a front, associated with a low in the
Bering, moves over the eastern Bering and Alaska Peninsula, cloud
cover will become more widespread along with chances of rain
increasing over the Bristol bay area. The remaining parts of the
domain should remain mostly dry due to moderate southeasterly flow
aloft. As pressure gradients increase due to the front tracking
closer to the Southwest, winds will increase along the coastal
locations and through gaps, especially through the Kamishak Gap.
Winds will gradually relax Friday as the low exits eastward from
the domain.

&&

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

Gusty northwesterly winds will slowly subside near Nikolski this
evening on the backside of a strong low that has been impacting
the Central Bering over the past two days. The aforementioned low
is moving south into the North Pacific and will leave the domain
by tonight. An upper-level low moving east out of the Kamchatka
Peninsula will merge with another shortwave in the northwestern
Pacific to form another storm force low. Storm force winds will
impact the western Aleutians Wednesday afternoon once cold air
advection takes place. Therefore, expect lower temperatures and
gusty winds on the backside of the aforementioned low as it
impacts the domain. Ahead of the low, in the warm sector, a gale
force front and rain will move east across the Chain through
Thursday. As a result of this frontal passage, southeasterly gusts
through gaps and passes Thursday are expected. Strong gale force
winds and precipitation will reach the Pribilof Islands Wednesday
into Thursday with winds gradually decreasing through Friday as
well as the chance of precipitation. With this, reductions in
visibility may be possible Thursday. Uncertainty still remains
with the exact track of these winds and precipitation, so stayed
tuned for updates!

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

Gulf of Alaska: Low pressure south of Kodiak Island will extend
a front to the northern Gulf for Friday. Easterly winds of 20 to
30 kt with low end gales up to 40 kt are possible from the Barren
Islands to Kayak Island for Friday into early Saturday as a
barrier jet forms ahead of the front. Winds will then diminish
through Saturday as the front weakens. Waves of 5 to 10 ft will
prevail across much of the Gulf, with waves along the northern
Gulf building to 10 to 15 ft along the northern Gulf for Friday
into early Saturday in association with the strongest winds.
Forecast confidence for this outlook is high.

Bering Sea: A north Pacific low south of the Aleutian Chain will
move east into the western Gulf through Friday. Widespread
easterly winds of 20 to 30 kt from Bristol Bay to the Pribilof
Islands Friday morning will turn more northerly and diminish
through the day. Northwesterly gales are likely along the backside
of the low, with these winds diminishing across the central
Aleutians by late Friday and the eastern Aleutians on Saturday.
Seas of 10 to 15 ft are expected across the southern Bering with
seas of 15 to 20 ft possible on the Pacific side of the central
and eastern Aleutians through Friday. Seas will subside to less
than 10 ft Saturday into Sunday. Southerly winds increase to 20 to
30 kt with seas building to 10 to 15 ft across the western
Aleutians/Bering for Monday in advance of a Kamchatka Low.
Forecast confidence for this outlook is high.

&&

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

A large upper-level trough extends from eastern Russia south and east
to the Gulf of Alaska, bookended by a retreating upper-level
ridge downstream over the Canadian Rockies and a second ridge
building over the western Aleutians. The trough is anchored by an
upper-level low situated at its base, weakening and moving east
from south of the AKPen to the southeast Gulf of Alaska through
the weekend. By Monday, this feature slides farther south as the
aforementioned ridges strengthen and phase into a larger blocking
ridge, extending from the central Aleutians to the Canadian
Arctic. A series of shortwaves moves from the western Bering to
the west coast of the state through Tuesday; however, these weaken
quickly as the ridge remains over much of the state.

At the surface, this translates to an area of low pressure moving
from well south of Kodiak Island Saturday to the eastern Gulf by
Sunday, exiting the region for Monday. Its associated front will
remain along over the northern Gulf through early Sunday, keeping
conditions unsettled. However, the front falls apart and
conditions improve for the second half of the weekend and into the
next work week as the ridge builds and a northerly flow ushers in
a drier airmass. Clouds may linger across interior Southwest
Alaska Sunday as the first of two shortwaves moves onshore and
weakens. As the ridge axis moves over Kodiak Island and extends
northeast for Monday, the resulting southwesterly flow in its wake
will bring clouds and a few showers to the Kuskokwim Delta Monday
into Tuesday as the second wave approaches the coast.

With the bulk of the unsettled weather remaining along the coast and
a ridge building over much of the Southern Mainland, expect a
gradual warming trend for Southcentral into next week. Average
temperatures this week will climb above average through the
weekend and into early next week. Daytime highs are expected to
push into the mid to upper 50s across interior Southcentral and
into the low 50s along the coast. For Southwest Alaska, expect
daytime highs in the mid to upper 40s inland and in the upper 30s
to low 40s along the coast, as higher cloud cover and an onshore
wind limit the amount of warming.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 177 178
         Gale Warning 155 165 170-176 179 411-414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS
MARINE/LONG TERM...TM