328
FXAK68 PAFC 011325
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
525 AM AKDT Mon Sep 1 2025

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

Discussion:

Not much has changed with the synoptic pattern over the past 24 hrs.
Still have a ridge of  high pressure settled over the Gulf with
long wave trough and associated upper low over the Bering. A good
fetch of moisture is still being pulled northwards between the
Gulf high and the Bering low. Since yesterday, several shortwave
troughs have moved around the base of the low and lifted north
across western Alaska. Water vapor satellite imagery shows another
shortwave starting to get its act together as it lifts north
towards the southern AKPen from the Northern Pacific later this
morning. As such, another push of light rain will work its way
eastwards from the AKPen and Bristol Bay region up the Cook Inlet
and Susitna Valley. Once again, most of the light rain will be
confined to the western side of the Inlet and Susitna Valley. A
coastal ridge has been building overnight with gradient increasing
over the Kenai and Chugach Mountains. By late morning, typical
gap flow areas such as the Turnagain Arm, Knik, and Copper River
will increase in response to the strengthening gradient. Hi-res
guidance is hinting at some downsloping along the western Kenai
Peninsula and Anchorage Bowl, but some showers may be able to
sneak through. Gusty winds are possible for the areas through
Tuesday morning when the gradient is set to relax.

The quasi-stationary front over Bristol Bay and the AKPen will
receive a reinforcing nudge with this next shortwave then another
nudge as the parent low opens into a wave as it moves over Alaska.
This will shift showers eastwards Monday night through Tuesday
morning. Beyond Tuesday, model solutions begin to differ more
significantly, but the NAM and GFS both have a low moving up
towards Bristol Bay by Wednesday.

- PP

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA / BERING SEA / ALEUTIANS
(Monday to Wednesday)...

Labor Day will be a rainy affair for much of Southwest Alaska on
Monday. An upper-level trough remains entrenched over the Bering
while, at the same time, enhanced Pacific moisture is streaming
along a slow-moving front over Southwest Alaska. Widespread
rainfall will continue moving into Bristol Bay and the Western
Alaska Range through this afternoon before a front finally shifts
east and into the Southcentral side of the Alaska Range. Rainfall
will taper off once this occurs, likely later this evening,
setting up a day of drier weather on Tuesday.

Offshore conditions over the Bering on Monday will be breezy as
the aforementioned upper-level trough gradually pivots eastward.
Beneath the trough, small craft winds and gales will clip the
Pribilof Islands later this evening, eventually overspreading
Nunivak Island and the YK Delta through Midnight tonight. Winds
then weaken into Tuesday morning.

The biggest story, aside from an extended period of rainfall
finally coming to an end across Southwest Alaska tonight, will be
the one day of drier conditions forecast on Tuesday. A North
Pacific low and front will lift northward into the Alaska
Peninsula late Tuesday with another round of widespread rainfall
forecast to spill into Southwest Alaska through Wednesday. There
are still some discrepancies, however, between forecast models,
with the ECMWF slower and stronger with the next system, while the
GFS and NAM are a little faster. While not committing to specific
timing and placement of the track of the low, more rainfall is
all but a given. The slower solution of the ECMWF would keep the
heaviest rainfall offshore of the coast. The solution of the GFS
and NAM would favor moisture moving directly into Southwest
Alaska. Areas across Bristol Bay and the Kuskokwim Valley could
see anywhere from another half inch to an inch or precipitation
through Wednesday night. Stay tuned to later forecasts as we work
on sorting out the finer details.

BL

&&

.LONG TERM FORECAST (Days 4 through 7 - Wednesday through Sunday)...

While a stubborn ridge remains centered over the Gulf of Alaska, a
fast-transiting North Pacific low will have made its way north and
will be transitioning across the boundary between the East
Aleutian Borough and the West Aleutian Census Area by Wednesday
morning; this low will bring heavy rain with a deep moisture
fetch and gusty gap winds to the Eastern Aleutians and AKPen
Wednesday and the Southwest Coastline, Bristol Bay to the
Kuskokwim Delta, on Thursday. A long- wave ridge will be affecting
areas further west along the Aleutians through this period, while
southcentral will remain relatively quiet with the ridge to the
south, though gusty gap winds along the PWS and Alaska Range will
be prevalent.

Once the aforementioned low breezes towards the north-Interior,
the two ridges of high pressure, which once bookended the low,
will slowly weaken, creating a messy pattern over mainland Alaska
by early Friday.

Turning west, a deep low will move out of the northwest Pacific
and extend into the western Aleutians as early as Thursday
morning, quickly becoming the prevailing driver across the
Southwest, Pribilofs and the Aleutian Chain. Meanwhile, weak
ridging will continue to prevail across Southcentral, with
chances for winds and rain ahead of the barreling low move into
Kodiak and areas north and east over the course of the day Sunday.
There are model differences as to how quickly the low will
transition out of the Pacific, into the Bering and then inland at
the end of this forecast period, which will dictate wind and rain
timing across Southern Alaska, so stay tuned for updates.

AB

&&

.AVIATION...

PANC...VFR conditions are expected to persist through the TAF
period. Ceilings of 5,000 feet with a scattered lower deck are
also possible at times during. The most likely time for these
lower VFR ceilings will be late this afternoon to early evening.
Chances for light rain also increase during this evening with
periods of showers lasting into Tuesday morning.

Light and variable winds early this morning become southeasterly
and increase as the day goes on. Southeasterly Turnagain Arm winds
bend into the terminal today through Tuesday morning. Peak winds
look to occur this afternoon through tonight with gusts reaching
up to 25 kts at times. Southeast winds remain Tuesday morning but
gusts should be below 20 kts before diminishing further Tuesday
afternoon.

&&


$$