693
FXAK68 PAFC 190029
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
429 PM AKDT Mon Aug 18 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA
(Monday afternoon through Thursday)...

Another fairly unseasonably warm and sunny day is underway across
much of the western half of Southcentral as the region remains
under the influence of a shortwave ridge axis that currently
extends from the Cook Inlet region northeast to the Copper Basin.
From parts of the Kenai and Chugach Mountains on east, a swath of
low to mid level clouds has developed along with a few light
showers being spurred off by a few weak impulses riding over the
top of the ridging in place aloft. The cloud cover in particular
has kept much of the Copper Basin and Prince William Sound a
little on the cooler side in the 50s to low 60s, while the much
clearer skies and sun have helped much of the Mat-Su and Anchorage
approach or exceed 70 once again. A weak Turnagain Arm wind has
begun to bend into the west side of the Anchorage Bowl, and this
south wind will likely continue well into tonight.

A much cooler and wetter day remains on track for Tuesday as a
well-defined Arctic trough digs down from the Interior into the
western half of Southcentral. Lift and divergence aloft ahead of
the trough will support bands of light to moderate rain
progressing from northwest to southeast throughout the course of
the day, starting first of the Susitna Valley in the morning and
eventually progressing out to Valdez and Cordova by the afternoon
and evening. The heaviest rainfall amounts ranging from about 0.3
to 1.3 inches should be mostly focused over higher terrain, where
southwesterly flow ahead of the approaching trough will enhance
rainfall rates via upslope flow into the Chugach Range and
Talkeetnas. It remains a bit less clear how much rainfall will
make it to the surface at lower elevations around the Cook Inlet
and western Kenai Peninsula, where the preceding air mass will
start out notably warmer and drier. There could be a sharp
gradient in rainfall amounts across the Anchorage Bowl as well,
with the higher amounts concentrated towards the Hillside and
Eagle River.

On Wednesday morning, most of the energy following the trough will
close off into an upper level low, then continue south before
merging with separate low pressure system drifting south of the
Gulf. This will yield a bit of a featureless synoptic pattern over
Southcentral for Wednesday and Thursday, as the remainder of the
trough erodes in place while upper ridging rebounding over
Southwest tries its best to spread back over the Alaska Range.
Weak winds coupled with moisture left behind from the recent rain
could make for ideal conditions for at least patchy fog to develop
across parts of the Mat-Su Valley and Anchorage early Wednesday
morning, especially if higher level clouds manage to clear up
early enough in the day. Both Wednesday and Thursday should be a
little warmer and drier compared to the cool and wet day expected
for tomorrow, but it will not be nearly as spectacularly warm and
sunny compared to what we`ve enjoyed the past two afternoons.

-AS

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
Days 1 to 3: (This afternoon through Thursday afternoon)...

The forecast remains largely on track, with increasingly active
weather as we head through the week. Forecast confidence is
moderate, with lowest confidence regarding the extent and density
of fog. This will affect forecast high and low temperatures, with
the potential for the diurnal temperature range to be smaller than
currently forecast. Additionally, forecast confidence is lower
regarding two storms impacting the Western and Central Bering from
late Wednesday through Thursday afternoon. This means there is
more uncertainty regarding the wind and precipitation forecast for
this area, for now.

Diving into the details...A low south of the Alaska Peninsula
exits into the North Pacific through tonight. As it departs,
northerly gap winds increase along the Eastern Aleutians and
Southern Alaska Peninsula. A front currently moving into the
Western Bering will move northeastwards across the Bering Sea,
bringing southwesterly winds to 30 kt and light rain to the
central Bering before weakening Wednesday afternoon. Behind this
front, increasing sea level pressure and an influx of warm, moist
air will likely lead to low stratus, and could lead to areas of
fog. The current fog forecast for the Bering Sea leans a bit
aggressive; this area may be trimmed down in successive forecast
updates as we get a better sense of how favorable the environment
may be for fog. Otherwise, the next features to watch for will be
a weak low moving moving into the Bering Sea Wednesday evening,
followed by a stronger low moving near the Kamchatka Peninsula.

For Southwest Alaska, upper level shortwave troughs will bring a
slight chance of showers to Kuskokwim Delta through this afternoon.
Tomorrow morning, a stronger trough will bring widespread rain
chances to the Kuskokwim Valley. By Tuesday afternoon, skies will
begin to clear across Southwest Alaska as transient ridging moves
in. This will lead to cooler nighttime temperatures from Tuesday
night into Wednesday morning, with overnight lows dipping into the
low 40s and perhaps even into the high 30s for Kuskokwim Valley.
Clearer skies will be short-lived, however, as cloud cover returns
with the approaching Bering Sea front Wednesday afternoon. With
the front weakening as it approaches, rain chances will be fairly
low (at around 15%).

-Chen


&&

.LONG TERM FORECAST (Friday through Tuesday)...

For the Bering Sea, the Aleutians and Southwest Alaska: The ridge
of high pressure begins to break down this weekend and retreats
southward into the North Pacific early next week. Simultaneously,
rounds of precipitation flow through the Bering Sea as a strong
low moves toward the Bering Strait. Early in the weekend, these
waves of moisture are forced around the northern side of the high.
As the high flattens and moves southward, signals point toward an
atmospheric river influence early next week resulting in more
widespread precipitation in the Aleutians and the Southwest
Mainland.

For Southcentral: an upper-level low moves through the Interior
this weekend resulting in mostly cloudy skies and waves of
moisture and rain through early next week.


&&

.AVIATION...

PANC...VFR conditions and light winds will persist through this
afternoon. The Turnagain Arm wind is expected to bend towards the
terminal by late afternoon / early evening, with southerly gusts
to 18 knots developing by 06Z. Winds will peak between 06-09Z then
decrease becoming more westerly to light and variable. Ceilings
will lower to about 5 kft by Tues morning and continue to lower
into the afternoon as rain showers begin to move in from the
north.

&&


$$