300
FXAK68 PAFC 271326
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
526 AM AKDT Mon May 27 2024

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

A wet morning is underway across much of southcentral Alaska. As of
5am, radar imagery shows a band of precipitation stretching from
approximately the Talkeetna Mountains and northeastern Susitna
Valley southwards through the Anchorage and portions of the
western Kenai Peninsula. Farther east, a potent shortwave trough
on the northern periphery of a low parked across the Northeast
Pacific is bringing precipitation to areas along the Gulf of
Alaska Coast, as well as much of the Copper River Basin. Overnight
rainfall observations show around a tenth of precip for much of
Copper River Basin and about a tenth or two across much of the
eastern Susitna Valley south through Anchorage. The winners
overnight have been the Palmer area and also McCarthy, both of
which picked up in excess of 0.30".

Precipitation across the east will continue through much of the day,
with the heaviest precipitation focused along an axis along and east
of the Richardson Highway. Farther west, the current band of
precipitation is expected to gradually pivot and diminish as the day
progresses. Should enough breaks in cloud cover occur, heat-driven
instability may spawn a few showers, particularly across the
northern Susitna Valley where breaks are most likely.

As we head into midweek, much of the same is expected... though
admittedly this becomes a rather difficult pattern to diagnose.
Southcentral Alaska will continue to sit in an area just north of an
upper-level low and then troughing in the Gulf of Alaska w/
several upper-level waves propagating westward from Yukon. Strong
waves will bring more stratiform rain and consistent cloud cover,
but weak waves and the edge of stronger waves may result in breaks
in clouds, but also daytime instability and possibly showery
precipitation. In any case, the Copper River Basin and surrounding
area (eastern AK range, eastern Chugach, Wrangells) will be in a
rather active and potentially wet pattern for days to come. The
Susitna Valley south through Anchorage and the Kenai Peninsula are
much more uncertain, but some rain-making mechanism will be
possible each day.

Forecast certainty is a bit higher for Kodiak Island where some
isolated showers are possible today and Tuesday, but then
widespread and steady rain is likely for Wednesday as a front
pivots into the island from the southwest.

-Brown

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3)...

Southwest Alaska is expected to remain dry for yet another day as
weak high pressure ridges inland from the eastern Bering. This
will also promote mild winds over the region today and tomorrow.
Morning satellite imagery shows continued low stratus and fog
situated over the Bering with a small area of clearing located
over the Kuskokwim Bay down and offshore of the Nushagak
Peninsula. A broad front extends southeastward from the western
Bering into the Eastern Aleutians. This front is bringing showery
conditions and an axis of southeasterly winds gusting between 25
to 30 knots. This axis of wind and rain will spread east through
this afternoon, reaching Nikolski later this morning and Unalaska
this afternoon, before stalling and slowly weakening.

Into Tuesday a surface low is forecast to develop along the front
somewhere immediately north of the Eastern Aleutians. Enhanced
southeasterly flow will become more prominent through the Alaska
Peninsula with increased gap winds out of the usual locations.
Across Southwest, a shortwave trough lifting out of the North
Pacific will promote renewed shower chances from Bristol Bay into
the Lower Kuskokwim Delta and Lower Kuskokwim Valley. While
thunderstorm chances are less certain, it appears isolated wet
thunderstorms will be possible with an area of weak instability
developing over the Middle Kuskokwim Valley late in the day. Any
activity that does develop should get carried northwestward within
broad southeasterly flow aloft.

By Wednesday a surface low over the Eastern Aleutians will begin
to weaken and fall apart. Shower activity and winds over the
Alaska Peninsula should gradually diminish over the course of the
day. The Aleutians and Southwest should experience below normal
temperatures while the low remains as well as general cloudiness.

-BL

&&


.LONG TERM FORECAST (Days 4 through 7) Thursday through Sunday...

By Thursday, a low pressure system will center itself near the
Alaska Peninsula and stay situated until midday Friday. Widespread
precipitation across Southwest is possible until a deep upper-
level trough enters the Western Bering on Friday and causes the
low to dissipate. The new trough will traverse across the
Aleutians through the weekend before ending up near the western
Gulf of Alaska. The exact trajectory of the system is still
unknown, with some models keeping the trough north of the
Aleutians through Sunday morning and other models pushing it
south as early as Saturday.

Over Southcentral, easterly flow will persist into Friday
afternoon as ridging continues to build in from Western Canada
over mainland Alaska. This will help support the formation of
afternoon showers as easterly waves and increased instability
build up over the course of the week. Weaker troughing will
persist over the Gulf through the forecast period until the
upper level trough from the Aleutians enters the Gulf. Model
guidance is suggesting a compact shortwave low could form and
impact parts of the northern Gulf Friday afternoon and evening.
The low is expected to dissipate over the Gulf by Saturday, but
the exact location is still unknown. The upper-level trough from
the Aleutians entering the Gulf on Sunday will provide unsettled
weather for most of the Southcentral coast as it looks to linger
over the area going into next week.

-BS

&&


.AVIATION...

PANC...VFR conditions and light winds will persist. Scattered
showers near the terminal this morning and ceilings at times
close to MVFR range should lift and scatter out as showers
dissipate by later this morning.

&&


$$