471
FXAK68 PAFC 300115
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 PM AKDT Tue Jul 29 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA
(Days 1 through 3: This afternoon through Friday evening)...

Currently, a vertically stacked low continues to spin in the North
Pacific south the of the Gulf while another upper low spins over
the Arctic. A ridge remains in the eastern Bering Sea with another
ridge to the east in Yukon, Canada. The two lows will send
converging shortwaves through Southcentral Alaska late tonight
and through Wednesday.

A shortwave from the Arctic low will pivot southeastward from the
Norton Sound region to the Susitna Valley late tonight. At the
same time, an easterly wave will rotate around the Gulf low and
move into the Southcentral around the same time. The result will
be band of widespread precipitation from the Western Kenai
Peninsula northward through the Mat-Su Valleys, including
Anchorage, late tonight through Wednesday with the heaviest rain
falling Wednesday morning into the afternoon hours. Steady rain
tapers off to showers late Wednesday evening. Elsewhere, isolated
thunderstorms are possible along the north and south sides of the
Wrangells for Wednesday afternoon into the evening hours as there
looks to be just enough instability in the eastern Copper Basin,
near the thermal low, to generate a few lightning strikes.

Showers will once again be possible across Southcentral for
Thursday as additional easterly wave move across the area from
Yukon, Canada. The best chances for isolated thunderstorm
formation will be across western portions of the Copper Basin,
along the Kenai Mountains, as well as along the Chugach Front
Range and Hatcher Pass. Forecast confidence decreases for Friday
mainly due to the timing and progression of a stronger easterly
wave rotating in from the Gulf. Friday does look to be wet across
the coast and eventually through the interior. However, the
question remains unanswered to this point whether steady rain
starts in the morning or holds off until the afternoon. Stay tuned
as we look to get a better handle on the Friday system.

&&


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

Currently, a vertically stacked ridge of high pressure is
situated across the Eastern Bering Sea and into parts of Southwest
Alaska. Aloft, the ridge is trying to break down as Southwest
Alaska is also feeling the effects of an Arctic trough of low
pressure to the north, with embedded shortwaves rotating around
its periphery. At the surface, the marine layer of low stratus and
fog has been pushed to the south across the AK Pen, which has
allowed Southwest Alaska to warm well into the upper 60s and 70s
this afternoon. Given daytime heating, clearing skies, and
influence from the trough, isolated thunderstorms cannot be ruled
out for the Bristol Bay coast this evening.

Looking westward to the Western Aleutians, an area of low
pressure is poised to move into the area Wednesday morning,
bringing a swath of rainfall and gusty winds with its front from
Shemya to Adak. This low deepens and moves northward into the
Western Bering Sea by Thursday morning as its front makes progress
across the Central Aleutians. Thursday into Friday, the forecast
becomes quite murky with the details as most models diverge in
timing, placement, and strength of a secondary area of low
pressure that moves towards the Western Aleutians. Forecaster
confidence is below average at this time, and the hope is that
models come into better agreement over the next day or so.

-AM

&&

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

Starting with the extended forecast period on Saturday, the key
features will be a deep low/trough in the Bering Sea, ridging over
mainland Alaska, and an upper level low somewhere in the Gulf of
Alaska or Northeast Pacific. Model guidance varies with the exact
placement of each of these features, introducing some uncertainty
into the forecast right off the bat. Honing in on the most impactful
weather, a frontal system will track toward the Southwest AK coast
on Saturday. The GFS has been consistently further north with the
Bering trough and more aggressive in pushing the front onshore of
Southwest AK, bringing rain and strong southeasterly winds to the
nearshore coastal waters from the Kuskokwim Delta coast to Bristol
Bay. The Canadian/ECMWF as well as ensemble data supports a
further south low position with the front elongating and weakening
off the Southwest coast. The current forecast represents this
latter solutions, with the strongest winds just off the coastline
and less rain and wind pushing onshore. In any case, the remnant
low will sit over the Bering Sea and slowly weaken through
Tuesday. With cooler air aloft, do think the extent and severity
of low clouds and fog currently being experienced over the Bering
Sea/Aleutians/SW Alaska will greatly diminish for the extended
forecast period.

Meanwhile, model spread with the low in the Gulf grows quite large
by early next week. Starting Saturday, there is fairly high
confidence that short-waves rounding the top of the low will
track westward into Southcentral, but low confidence in exactly
where the most likely areas for rain will be. Despite the
radically different solutions for low placement on Monday, all of
the guidance indicates the low exiting eastward, which will lead
to mostly dry conditions across Southcentral and Kodiak Island.
Models are then completely out of phase with the upper level wave
pattern (placement of troughs/ridges), making it very difficult
to hone in on potential weather impacts.

-SEB

&&

.AVIATION...

PANC...Wind direction will be the main challenge for the forecast
period, especially this afternoon through evening. The uncertainty
revolves around whether the wind blowing through Turnagain Arm
will be able to bend into west Anchorage and over the airport or
whether it will remain to the south of the airport and inducing an
eddy off the core of stronger winds resulting in West or
Southwest winds for this afternoon and evening. By late evening,
the synoptic pattern will favor south-to-southeast winds up to 10
kt through Wednesday.

Otherwise, VFR conditions will persist through the night. For
Wednesday, there will be a chance for occasional MVFR conditions
in light rain.

&&


$$