Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 260057
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 PM AKDT Sat Jun 25 2022

.ANALYSIS AND UPPER LEVELS...

A large area of high pressure over the Gulf is funneling plenty
of moisture up Cook Inlet in the from of a widespread marine layer
that has enveloped all of Cook Inlet, and extends into much of
the western Kenai Peninsula (except the Homer area), Anchorage,
and the Mat-Su. Some erosion of the cloud cover from the north in
the Susitna Valley is allowing for increasing sunshine in those
areas, but much of that area remains socked in the clouds. As is
much more usual, the marine stratus extends across nearly all of
the Gulf, Kodiak, and Prince William Sound.

Meanwhile across the west, a large low centered near the Pribilof
Islands is spreading increasing clouds across most of Southwest
Alaska, especially coastal regions. Associated rainfall is just
beginning to move ashore. In contrast, mostly sunny and smokey
conditions persist along the Alaska Range this afternoon, where a
Red Flag Warning remains in effect. More on that below. Widespread
Bering and Pacific stratus is keeping the entire basin under
nearly overcast skies, with highs only in the 40s out towards
Shemya.

In the upper levels, a large high is over the Gulf, overspreading
much of mainland Alaska, while a deep trough and embedded upper
level low is over the southern Bering. In between, southerly flow
is drawing the surface low and Pacific moisture northward, though
any substantial precipitation not associated with convection is
confined to the eastern Bering and the AKPEN.

&&

.MODEL DISCUSSION...

The models are in excellent agreement through Monday afternoon as
the stationary pattern prevalent over all of mainland Alaska
persists. The main points of uncertainty are the westward extent
of Red Flag conditions through Sunday, and where any convective
activity over the Copper River Basin develops. Overall forecast
confidence is very high.

&&

.AVIATION...
PANC...Light westerly winds will persist through the TAF period.
The marine stratus held in very strong much of today, and the burn
off of the clouds this afternoon and evening will quickly return
tonight and repeat in a very similar way again on Sunday. Thus,
expect IFR ceilings to be predominant tonight through early-mid
Sunday afternoon, with brief clearing again Sunday afternoon and
evening.

&&

.FIRE WEATHER...

Southcentral: Besides the lack of any kind of much-needed, significant
rainfall anytime in the near future, the main fire concern will be
continued isolated thunderstorms over the Copper River Basin the
next few days. While the most thunderstorm activity will be this
afternoon and evening as compared with Sunday or Monday, each day
will feature slightly hotter and slightly drier conditions than
the day before. Gap winds may increase at times, but appear most
likely Sunday and Monday nights, which should be sufficiently
offset from the hottest and driest time of day. Along Cook Inlet,
with marine stratus in place today and no meaningful change to the
weather pattern the next several days, expect the marine stratus`
presence each day for at least the first half of the day, which
should greatly reduce temperatures and increase RH values as
compared with previous sunny days.

Southwest: A Red Flag Warning remains in effect for the western
Alaska Range for hot, dry, and windy conditions this afternoon and
evening. Conditions may be pretty similar again on Sunday in this
same area. With a bit more cloud cover possible temps and RH
values will be somewhat better/less favorable for fires, but with
the front over the Bering moving closer, expect stronger winds in
this area. Conditions are not expected to quite make warning
criteria along the foothills of the Alaska range on Sunday, but
heightened fire weather conditions will continue. The remnants of
the front fully move over Southwest Alaska on Monday. While
rainfall will be minimal, overcast skies, diminishing winds, and
more influx of Pacific atmospheric moisture will greatly improve
fire weather conditions.

&&

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

With a large bank of marine stratus sitting in the Gulf, cooler
and moister conditions are in store along Cook Inlet and the Gulf
coast in the short term. Cloud cover will likely build over
Western Kenai Peninsula, Anchorage, and parts of the Mat-Su
Valleys for both Sunday and Monday as southerly, up-Inlet flow
continues. There remains uncertainty with how quickly the marine
stratus will dissipate during the day, which will affect highs in
the Cook Inlet region. This influx of cleaner air from the Gulf is
expected to help gradually clear out residual smoke and haze near
the coast. Haze will be slower to clear out further inland,
especially due to subsidence under the ridge.

While conditions remain relatively stable near the coast, clear
skies and abundant surface heating will support convection over
the Copper River Basin for the next several days. While convection
is expected across Copper River Basin this afternoon and evening,
showers and isolated thunderstorms are expected to remain mostly
along the Wrangell Mountains and Alaska Range tomorrow and Monday.
Tuesday could be a day to watch as weak shortwaves and highs
around 80 in the Copper River Basin may support more intense
thunderstorm activity.

&&

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

A cooler, cloudier, and wetter pattern is expected for much of
Southwest through the forecast period. The one exception to this
will be the Western Alaska Range/Lake Clark National Park area
where hot, dry, and windy conditions are expected to continue
through Sunday. A low pressure system southwest of Nunivak Island
will continue pushing its front onshore to Southwest overnight and
through the day on Sunday. As a result, expect wetting rains for
much of the coastal areas, especially north and west of
Dillingham, the south facing slopes of the Aleutian Range on the
Alaska Peninsula, and coastal areas of the Kuskokwim Delta
including Kipnuk to Toksook Bay. The steadiest and heaviest
rainfall will be this evening through Sunday where 0.75 to 1.25
inches of rain is expected. Heaviest amounts north and west of
Dillingham and along the upslope facing side of the Aleutian
Range. Mostly downsloping is expected along the north side of the
Alaska Peninsula due to deep southeasterly flow but a few showers
cannot be ruled out. Gusty southeasterly winds are also expected
to continue through Sunday night before diminishing as the
pressure gradient and front across the area weakens. The strongest
winds will remain across the immediate coastal areas where gusts
up to 50 mph are possible, especially along the Alaska Peninsula
(Nelson Lagoon to Egegik).

The front continues pushing inland Monday while decaying
(frontolysis) with most of the rain shower activity dissipating
by Monday night. Expect mostly light and variable winds for Monday
through Monday night.

Lastly, upper level ridging builds into much of Southwest for
Tuesday bringing the return of drier, warmer, and sunnier weather.
Instability will also start to increase on Tuesday especially near
the Western Alaska Range where afternoon and evening rain showers
are possible. There also may be some activity over the Ahklun
Mountains. Anything that does form here could move over the lower
elevations of the Kuskokwim Delta due to the southeasterly
steering flow. Therefore, an isolated rain shower is possible
around Bethel.

&&

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

Upper level troughing is expected to remain over much of the
Bering and Aleutians through the forecast period. This will
continue to result in unsettled weather conditions through the
next couple of days. Another low pressure system will move through
the Western Aleutians (Shemya) Sunday afternoon. This low
continues moving eastward through Monday before moving northward
into the central Bering by Tuesday morning. Its associated front
continues moving along the Chain through Tuesday afternoon
bringing periods of rain to areas such as Adak and Atka
Monday through early Tuesday. The front slows and down and
virtually stalls west of Dutch Harbor on Tuesday while weakening.

&&

.MARINE (Days 3 through 5: Tuesday through Thursday)...

Bering Sea/Aleutians: A low crosses the Aleutians into the
Southern Bering on Wednesday. Its front extends across the
central Aleutians and moves into the eastern Aleutians by
Wednesday morning. Good confidence in a few localized gale force
gap winds possible with this front. Wednesday night, a second
North Pacific low crosses into the Bering and pushes its front
across the central and eastern Aleutians through Thursday.
Moderate confidence with southerly gale force winds along this
front. Seas remain below 20 feet.

Gulf of Alaska: With high pressure in place over the Gulf, winds
below gale force and seas less than 20 feet are expected for the
days 3 through 5 period.

&&

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

Looking ahead into the extended, ensemble guidance continues to
trend towards upper level ridging with higher heights to be the
story for Southcentral Alaska for the period. Although, there
appears to be reasonable deterministic agreement that a shortwave
will cross into the region from the southwest (Barren
Islands/Kodiak area) during the day on Wednesday. Most
precipitation and convection associated with this wave should be
confined to the favored upslope areas and higher terrain of the
Alaska Range/Talkeetna Mountains/Copper River Basin. The ridge
will slowly migrate east during the latter half of the period with
heights falling. However, confidence diminishes with exact timing
and evolution of additional upper level shortwaves moving through
the flow and frontal passages late week through the first half of
the holiday weekend. The odds favor that Southcentral will
continue to experience warmer than normal temperatures during the
extended period with slight chances of above normal precipitation
a change from the dryness over the past month.

For Southwest Alaska, there is good deterministic agreement of an
upper shortwave passing through Bristol Bay which could spark some
showers in the favored upslope areas of the Ahklun Mountains and
Western Alaska Range for Wednesday. Ridging nudges back in from
the south for Thursday with guidance hinting at quieter weather.
Guidance then hints at a more unsettled second half of the
extended period (Thursday night through Saturday) with onshore
flow and influence from an upper level low pressure system in the
Bering Sea. Confidence is low to average with exact timing and
evolution of the synoptic features such as associated shortwaves
and frontal passages. In general, expect continued unsettled,
rainy, and gusty weather for the Bering Sea and Aleutian Chain as
an active storm track remains throughout the area.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 165.
FIRE WEATHER...Red Flag Warning 163.

&&
$$

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


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