Small Craft Advisory 360, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
531 AM AKDT Fri Apr 29 2022

.ANALYSIS AND UPPER LEVELS...
Quiet weather across Southcentral Alaska into Friday morning with
scattered clouds inland and low stratus along the Gulf coast as
high pressure over the Gulf persists. To the west, a broad trough
with a few low centers are circulating along the Aleutians.
Rainfall is being reported at surface stations as moisture advects
through south to southeasterly flow over the eastern Aleutians
and the Alaska Peninsula. Dry air continues over mainland Alaska
and while reflectivity indicates that showery activity ahead of
the front, through the Bristol Bay and Kuskokwim Delta, it is
likely evaporating before reaching the ground.

&&

.MODEL DISCUSSION...
Models are all in good synoptic agreement through the weekend
even with the complex pattern of the low development and
progression from the Bering Sea into the Gulf of Alaska. Models
are keeping the northeastern Copper River Basin as the only area
that could see any diurnal shower activity the next few days.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Today through Sunday
Night)...

The quiet weather of the past week will end for some across
Southcentral this weekend. The leading front from a Bering low
will move into the western Gulf, particularly around Kodiak Island
this afternoon. The front will largely stall in place resulting in
a long period of steady rain on strong easterly winds through into
Sunday. A new low will develop along the front on Saturday, move
to just off the coast of Kodiak Sunday morning. The low will
gradually drift northeast on Sunday, then weaken as a second front
begins to absorb this low late Sunday night.

On this track, expect expect 2 to 3 inches of rain through Sunday
across Kodiak Island, with the highest amounts on east facing
slopes. As the front attemps to move north and the low develops
along it Saturday, more precipitation is expected along the
coastal mountains as well, especially the Kenai Mountains. Raised
rainfall totals in these areas a good bit from previous forecasts.
Finally, the gap winds will increase ahead of the front through
Turnagain Arm, the Knik River Valley, eventually the Copper River
Basin, and through Thompson Pass. Gusts of 30 to 40 mph are
possible through these gaps.

&&

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

A front extends over Southwest Alaska, fizzling out slowly over
the next couple of days. Gusty winds will continue through
tomorrow, diminishing through the overnight hours Saturday.
Strongest winds will be along the immediate coast, with areas near
Cape Newenham and Platinum already seeing peak wind gusts 40-50
mph. Winds further inland are not expected to be as strong, but
may still reach 25 to 35 mph. Rainfall over the AKPen will work it
way north, spreading into Bristol Bay and along the Kuskokwim
Delta Coast. Inland areas will likely remain cloudy and dry. As
the front dissipates, flow transitions to offshore, meaning drier
conditions and less aggressive cloud cover across Southwest.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Upper level elongated low sits over the Bering today and tomorrow
before moving off towards the Gulf. There are a few embedded
surface lows north of the Chain bringing rounds of widespread
rainfall to the Eastern Aleutians/southern AKPen through tonight.
Additionally, gale force winds will be prominent in the eastern
Bering and along the Southwest coast. North and south of the low
consists of widespread small craft winds and spotty light rain
showers. The low moves out by Saturday night as the front off the
next system moves over the Western Aleutians.

&&

.Marine (Days 3 through 5: Sunday through Tuesday)...
Gulf of Alaska: Expect widespread small crafts and periods of gales
along the north Gulf coast through Tuesday. High-end gales are
expected late Saturday into early Sunday as a front extends across
the Gulf. After a lull, a weakening low will push towards the
northern Gulf Monday morning, increasing winds to lower-end gales.
As a broad low crosses the AKPEN early Tuesday, its front will
bring another swath of gales into the north Gulf coast. Some
uncertainty persists with the finer details in the timing and
strength of these winds. Seas about 12 feet increase to near 20
feet where gales are expected.

Bering: A strong low tracking along the Aleutians will bring
widespread small craft winds and areas of gales. Easterly winds
across the Bering will become northerly as the low continues
moving east into the Gulf. Gusty, northerly gap winds are expected
south of the Eastern Aleutians and AKPEN on Tuesday. Seas up to
16 feet in the Bering and up to 22 feet in the North Pacific.

&&

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

With the jet stream winding near Southern Alaska and a longwave
trough overhead, expect unsettled weather to continue through the
extended period. Good model agreement at the synoptic scale
persists through Wednesday, with minor differences in timing and
other finer details. For Southcentral, the week will begin with
wet and windy conditions along the coast. First, a vertically
stacked low moves into the northern Gulf Monday morning, bringing
rain and enhanced winds along its front. Another vertically
stacked low makes its way into the Gulf Monday afternoon,
reinforcing winds and rain along the coast. Rain will linger along
the north Gulf coast into Wednesday as this second low weakens
and drifts across the Gulf. Model agreement deteriorates into
Wednesday regarding the descent of a shortwave from the Arctic.
The GFS shows the shortwave moving through Southcentral, In
contrast, the Canadian and Euro put the shortwave in Southwest
Alaska, with the Euro showing a weaker solution. The eventual
location of this shortwave will have implications on precipitation
potential and where gustier winds and lower temperatures should
be expected.

For Southwest Alaska and the Aleutians, the week will begin with
a low transiting along the Aleutian Chain and into the Gulf.
While winds will be elevated, the strongest winds will remain
further south in the North Pacific. Rain will slowly taper off by
Tuesday as the low moves into the Gulf. However, northerly winds
behind the low will keep gusty gap winds a concern along the
Alaska Peninsula and Eastern Aleutians through Wednesday. From
Wednesday through Thursday, weak high pressure builds in. Models
hint at a North Pacific low moving towards the Western Aleutians
Wednesday, though agreement is poor regarding its evolution. While
the GFS suggests the low will persist through Thursday, the
Canadian and Euro are quicker to have it dissipate.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 120, 130-132, 137, 155, 160, 165, 180,
                       351, 352, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ/VR
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
MARINE/LONG TERM...MK/KC