Small Craft Advisory 604, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 AM AKDT Wed Aug 3 2022

.ANALYSIS AND UPPER LEVELS...

A upper level shortwave passes over Southwest Alaska towards the
Gulf through tonight, meanwhile, a low is currently spinning in
the Bering, its front approaching the Southwest Coast this
morning. Amplification of the jet will help push the low in the
Bering off to the northeast, towards the Y-K Delta, and then
continue an eastward track. The trough extending off the low and a
series of embedded shortwaves will push across Southern Alaska
and into the Gulf through Friday afternoon. Another shortwave will
push across the Bering on the backside of the low on Friday, just
a head of a high pressure ridge setting up over the Western
Aleutians.

&&

.MODEL DISCUSSION...

Models remain in good overall synoptic agreement through the short
term. The shortwave dipping across Southcentral and into the Gulf
is represented well across all models. The next system is spinning
up in the Bering today. There is fair agreement until early
Thursday morning when there is some light inconsistencies as the
low moves onshore over the Y-K Delta.

&&

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

&&

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

A ridge is building over the area from the west while a shortwave
trough will ride over the top of the ridge moving in from western
Alaska. The ridge will bring warm temperatures with mostly sunny
conditions across much of the region. However, the shortwave
mentioned above will destabilize the atmosphere and allow a few
showers and thunderstorms to develop mainly over the higher
terrain of the Talkeetna Mountains, the Chugach Mountains and
Wrangells this afternoon. Tonight the ridge will move across the
area with mostly dry weather with the exception of a few
lingering showers over the high terrain as the shortwave drops
into the northeastern Gulf. Thursday a large area of low pressure
near western Alaska will bring southwest flow with a shortwave
moving into Southcentral. This will produce showers across the
area, but not all areas will get wet. Thursday afternoon a few
isolated thunderstorms are possible across the Wrangell Mountains
due to unstable air. Thursday night into Friday a stronger
shortwave will quickly move into Southcentral this will bring a
front into the northern Gulf. These features will bring widespread
rain across the region, with anywhere between a quarter inch to
an inch and a half or more of rainfall.

&&

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

Low stratus and fog are present over much of Southwest Alaska as
a shortwave ridge moves overhead this morning. With the Alaska
Peninsula located behind the front, somewhat stagnant conditions
could keep fog or mist around through the day. For the remainder
of the Southwest, fairer weather is expected for the first half
of the day. Temperatures will climb as high as the upper 60s as
sunlight penetrates the high to mid- level clouds currently
filtering in over the region. For the Western Alaska Range,
daytime heating in conjunction with incoming shortwave energy will
lead to showers at higher elevations. A few lightning strikes are
possible, though instability should be low enough to prevent
vigorous thunderstorms from developing. The occluded front will
slowly push onshore through the latter part of the day, bringing
elevated southerly winds to the Kuskokwim Delta as well as
overcast skies and increased rain chances over the region.

Cloudy, wet, and windy conditions continue for Thursday and
Friday as the occluded low center follows its front into
Southwest Alaska. Scattered to numerous showers around the low
center will track east across the region through Friday, with the
highest rain amounts expected along the mountains. Southerly winds
will pick up through Kuskokwim Delta and from Bristol Bay north
into the Lower Kuskokwim Valley. Late Friday night, a surface low
moves over the Bering Sea and into Kuskokwim Delta, bringing
another round of rain. For the Alaska Peninsula, an elongated low
sliding over a North Pacific ridge could bring a steady surge of
rain from Thursday through Friday morning. The placement of this
feature continues to be difficult to dial in, especially as the
narrowness of this low means that slight differences in position
could produce larger differences in rain amounts.

&&

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

A low in the Western Bering will slowly track towards the Y-K
Delta by Friday morning. Gales along the western and southern
edges of the low are expected through early Thursday morning as
cold air wraps around it. By Thursday, winds will drop to small
craft speed as the low occludes. Then, the focus shifts to an
elongated low that slides over a North Pacific ridge and into the
Eastern Aleutians and Alaska Peninsula. Some uncertainty persists
with the placement of this feature and where the highest rain
amounts will occur. For now, the Eastern Aleutians look to be
getting some periods of moderate rain with this feature. It's
also possible the Central Aleutians could see a bit more rain than
currently forecast. Aside from rain, this elongated low will also
bring small craft winds to the Pacific side of the Eastern
Aleutians and Alaska Peninsula. By Friday, much of the area could
see a return to low stratus and fog as high pressure builds over
the Bering Sea and Aleutian Islands.

&&

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

Gulf of Alaska: A wide area of low pressure over the Northern
Gulf digs in with upper level support through Sunday. Forecast
confidence is good. Widespread rain, locally heavy spreads over
the region. Gusty Southwest winds increase to gales Friday, and
moves across the Gulf, becoming Northwesterly gales through
Kamishak Bay and Barren Islands into the Western Gulf Saturday,
diminishing Sunday. Seas to 15 ft, subsiding.

Bering: High pressure remains over the Southern Bering and
Aleutians through Sunday. A series of weak lows from the Chukotsk
Peninsula move over the Eastern Bering through Sunday. Forecast
confidence is fair with the movement of the lows. Gusty Westerly
winds move across the Bering into Bristol Bay by Sunday. Seas to
10 feet.

&&

.LONG TERM FORECAST (Days 4 through 7 - Saturday through
Tuesday)...

Models have a relatively good handle on the weather pattern until
about Monday. Models are resolving a shortwave coming into the
Gulf Saturday and Sunday. The GFS and EC have this feature moving
slower, whereas the CMC and UKMET have it moving much faster.
Model spread really begins to grow as another shortwave will drop
through the Bering and through Southwest Alaska Sunday and Monday.
The GFS is much quicker with the aforementioned feature than the
other models. By Tuesday, some models are bringing the core of an
upper-level low into mainland Alaska, whereas, the GFS keeps it
farther north. However, a strong high pressure in both the upper
levels and at the surface is forecasted to retrograde and stall
across the mid-latitudes of the Pacific between Alaska and Hawaii.
This will result in a fairly progressive pattern across southern
Alaska. Chances of rain will increase for the Aleutians and
stretch eastward into the southern mainland through the forecast
period. Due to the aforementioned low edging southward toward
interior Alaska late next week, this will result in bringing
cooler temperatures to the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 177 178 411 412 413
FIRE WEATHER...NONE.

&&

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