515
FXAK68 PAFC 201316
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 AM AKDT Mon Jul 20 2026

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

The upper level trough will continue to become more negatively
tilted today while slowly progressing northeastward. Heavy rain
across the Kenai Peninsula and Susitna Valley is shifting back
north and east. A Flood Warning remains in effect for Seward, but
so far river gauges have yet to rise significantly past action
stage. A Flood Advisory is in effect for the Yentna River for
minor flooding of low lying areas along the river. In addition to
the aforementioned areas where flooding is expected, other areas
to closely watch for potential minor flooding include the
southwestern Kenai (Anchor River), other rivers and streams in the
Susitna Valley, and Anchorage (for urban flooding as rain spreads
back in this morning). The upper trough will weaken as it
continues north and east tonight through Tuesday. The upper jet
(and atmospheric river) will also weaken with time. As a result,
expand a narrow band of much lighter rain to spread across the the
Copper River Basin Monday night through Tuesday morning.

There will be a brief break in rainfall behind the upper trough
(24 hours or less) before the next storm approaches from the
Bering Sea in continued progressive flow aloft. Rain will reach
Kodiak Island Monday night, then overspread much of Southcentral
by Tuesday afternoon. The forecast has shifted slightly to
multiple storms slowly tracking from the Bering into the Interior.
Thus, rather than two periods of rain Tuesday and Wednesday, it
may be continuous rain starting late Tuesday and continuing
through sometime on Thursday. Ridging still looks on track to
develop starting Friday.

-SEB/CJ

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(Days 1 through 3:Today through Thursday morning)...

The cool and wet summer across Southwest Alaska continues through
the short-term period. Expect showers to continue for today,
especially this afternoon and evening across the Southwestern
Mainland. Some instability could build today with a few breaks in
the cloud cover. Showers could then tap into this extra
instability and become more robust at times than they otherwise
would be. The lightning threat is low (10%) for this afternoon
into the evening.

Showery activity today across Southwest all precedes the next
widespread rainmaker which comes in the form of a low currently in
the western Bering. This low moves east-southeast through today
with the front reaching the Pribilof Islands and and
Nikolski/Unalaska/Akutan by late this morning. Steady rain then
moves to the Southern Alaska Peninsula (AKPEN) starting this
afternoon. Rain advances up the AKPEN and makes it to Coastal
Southwest by overnight tonight/early Tuesday morning. Rain then
moves inland across Southwest from the coast through the rest of
Tuesday. Expect a push of southeasterly winds associated with the
front Tuesday morning through into Tuesday afternoon For Kuskokwim
and Bristol Bays before wins turn southwesterly through the rest
of Tuesday afternoon and evening. Wind gusts up to 40 to 45mph are
likely along the northern Kuskokwim Bay Coast Tuesday morning
with 35 mph for Bristol Bay. Bristol Bay will see the strongest
corridor of southwest winds, up to 30 mph through the Bay Tuesday
afternoon into early Wednesday before winds briefly diminish ahead
of the next system to move into Southwest on Wednesday. In
addition to the gusty winds Tuesday across Kuskokwim and Bristol
Bays, expect larger waves of around 10 ft in the coastal waters of
Kuskokwim Bay with 7 to 9 ft for Bristol Bay.

Yet another system will impact Southwest with more winds and more
rain for Wednesday as this system first gets its act together
over the Kamchatka Peninsula. This system will then move east and
into the western Bering by Tuesday afternoon. Moderate to heavy
rain along with gale-force southwesterlies are likely across the
Western Aleutians Tuesday. The corridor of southwest gales moves
to the coastal waters of Adak/Atka and the open central Bering by
Wednesday morning. Rain also spreads east to the Pribilof Islands
by early Wednesday morning and to Adak/Atka by late Wednesday
morning.

The heaviest rain will stay north with the "fire hose" pointed at
Southwest Alaska. Heavy rain makes it to the coast by late
Wednesday morning with light to moderate rain spreading inland
before that. Between Tuesday morning to Thursday morning as much
as 1 to 2.5 inches of rain looks to fall across the AKPEN and
Mainland Southwest Alaska. The higher-end totals will be along the
Bristol Bay coast as well as along the mountain ranges of
interior Bristol Bay, including the Western Alaska Range and
Northern Aleutian Range. Lower-end totals are likely across
Kuskokwim Bay due to being outside of the best moisture axis,
especially for Tuseday`s system. Rainfall totals decrease towards
the Southern AKPEN and Eastern/Central Aleutians. Stay tuned to
forecast updates regarding rainfall amounts; any small changes in
storm tracks for Tuesday and Wednesday could have implications on
where the best moisture axes set up. For now, the best location
for heavy rains Tuesday and Wednesday looks to be across Bristol
Bay with Tuesday being the wettest of the two days. Wednesday will
be the wettest day for the Kuskokwim Delta, Kuskokwim Valley, and
along the Western Alaska Range.

Aside from the heavy rain, southwesterly small-craft winds will
also be brought back into Kuskokwim and Bristol Bays. Depending on
how strong the pressure gradient will be between the storm center
that will be in the vicinity of Nunivak/Saint Matthew Islands by
Wednesday afternoon, and a strong ridge to the south in the North
Pacific, will dictate if sustained gales can reach into Bristol
Bay. Right now, there is a 50% chance of that occurring. Much like
the storm for late tonight/Tuesday, expect waves of 8 to 10 ft
into Kuskokwim and Bristol Bays for Wednesday. Wave heights will
slowly subside Wednesday night into Thursday as the southwest
fetch weakens. Rain will also taper to showers from northwest-to-
southeast beginning Wednesday evening with the Kuskokwim Delta
Coast and eventually across Bristol Bay for Thursday morning.
Steady rain will still be in place along the Western Alaska Range
Thursday morning.

&&

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

A pattern change is in the works during the long term period next
week. An upper low and front will be progressing through interior
Alaska on Thursday. Behind this feature forecast models are in
somewhat good agreement with the development of a building ridge
of high pressure over the southern Bering on Friday. The ridge
amplifies further over the weekend. For Southcentral, northerly
flow behind the departing upper low and trough will bring in drier
conditions and a potential break from persistent rain chances
over the state. High pressure over the Bering will favor drier
conditions as well. The one caveat will be the potential for
smaller shortwave disturbances to ride over the top of the ridge
and into Southwest Alaska with renewed rain chances on Sunday.

-BL

&&


.AVIATION...

PANC...The upper level trough associated with the atmospheric
river will push through today, bringing moderate rain with it.
Ceilings and vis are likely to drop to MVFR and IFR at times
during moderate rain. Turnagain winds should be done for the day
becoming westerly later in the day followed by up-inlet this
evening.

&&
$$