Flood in Alaska, May 5 to 7, 2025

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
543 AM AKDT Mon May 5 2025

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

The upper level low is currently circulating near Chirikof Island,
south of Kodiak Island. Its storm force barrier jet across the
northern Gulf is pushing inland this morning and dissipating to
gale force along the northeastern coast and directing into Prince
William Sound. Southeasterly flow is leading to gusty winds
through terrain gaps and light to moderate rainfall. To the
leeside of the mountains, downslope drying is expected to
generally persist through the short term. Some trace amounts of
spill over will remain possible. Winds through the Matanuska
Valley are blowing glacial dust across Palmer and may remain the
case into the early afternoon today. Looking east toward Thompson
Pass, winds are gusting to around 20 to 30 mph with snowfall.
Roadways may be slippery and the potential for reduced visibility
has led to a Winter Weather Advisory. The highest amounts of QPF
and wind speeds are expected over the next few hours this morning.
The front will push inland this afternoon and while parts of the
Copper River Basin could be downsloped, weak upsloping toward the
Wrangells and Alaska Range will increase the precipitation
probability.

The western Gulf low will track eastward over the first half of
this week and weaken. Generally models agree with the placement
and track, though the GFS is tending to be the more southerly
solution. Winds and precipitation will decrease each day into
midweek, but weather conditions will overall change little over
the next few days as the track of the low is rather slow. Farther
inland, some sun breaks will be possible over the next couple of
afternoons. Daytime heating and instability could pave the way to
isolated thunderstorms. The convective potential this afternoon in
the Matanuska and Susitna Valley will depend on how much sunshine
could heat the surface. By Tuesday afternoon however, there will
likely be enough instability with daytime heating from clearing
conditions and upper level energy to increase the possibility of
convective showers and storms for the Susitna Valley and also
upper Copper River Basin. Weaker flow appears more likely by
midweek as the low weakens in the Gulf. There is some uncertainty
involving the weak embedded shortwaves that could dip across the
Alaska Range into Southcentral. Convection is possible, but
moisture may not be quite as present as previous days and showers
could remain over higher elevations.

Rux

&&

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

Currently, the big low southwest of Kodiak Island continues to
spin in place this morning. Shortwaves rotating around the low
will continue to be the main driver for showery activity across
the southwestern mainland through Tuesday evening. Due to more
cloud cover today, thunderstorms are less likely across the
mainland. However, thunderstorm chances increase for Tuesday
afternoon into the evening as daytime heating builds and
instability increases, especially for the foothills of the Western
Alaska Range, Lower Kuskokwim Valley and Interior Bristol Bay.
Daytime highs for Tuesday look to be in the middle 50s, but could
reach the high 50s to near 60 degrees towards the Lower Kuskokwim
Valley.

An upper-level low will drop out of the Bering Strait region to
around St. Lawrence Island for Wednesday and Thursday while an
additional upper-level low remains across interior Alaska.
Shortwaves rotating around the upper low across St. Lawrence
Island with mesoscale waves around the interior low will be enough
to keep scattered showers in the forecast for each Wednesday and
Thursday afternoons. There could be enough instability across the
foothills of the Western Alaska Range and Lower Kuskokwim Valley
each afternoon to produce a few lightning strikes with more
vigorous showers that do develop.

Farther out west, gusty northerly winds continue across the
Eastern Aleutians and southern Alaska Peninsula (AKPEN) as the
pressure gradient remains tight between a ridge to the west and
the stubborn low southwest of Kodiak Island. These winds will
slowly diminish through Tuesday. The cold northerly flow will also
keep scattered rain/snow showers going across the Eastern
Aleutians and southern AKPEN through Tuesday before warmer air
begins to work in. The warmer air will come from a front that will
move across the Western and Central Aleutians this evening
through Wednesday morning when it makes it to the Eastern
Aleutians as it weakens. An additional North Pacific low and front
will bring a stronger push of warm air, rain, and gusty southerly
winds to the Western and Central Aleutians Wednesday evening into
Thursday morning.

&&

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

Thursday, a low in the southern Gulf quickly weakens and
dissipates by Saturday as a high amplitude ridge builds across
northwestern Canada. The final surface shortwave of this system lifts
across the southeastern Gulf to the northern Gulf coast from
Friday morning through Saturday afternoon. The upper level low
will linger over the Gulf through Friday before deformation causes
the remaining energy to dissipate.

Meanwhile, a deep low will track into the far western Bering Sea
Thursday, with a leading front sweeping across the Pribilofs and
eastern Aleutians through Friday morning. Despite the front's
rapid progress, ensemble consensus depicts the low's center
slowing as it tracks into the central and northern Bering,
remaining west of the Pribilof Islands through Sunday. A second
North Pacific low lifts across the Alaska Peninsula Sunday
morning, splitting between Bristol Bay and the Gulf of Alaska.

&&

.AVIATION...

PANC...VFR conditions persist through the TAF period, with
ceilings also expected to remain above 5000 ft. Low-level wind
shear is no longer expected, with the inversion and strong
southeast winds aloft at 5000 ft or higher. Light and variable
winds with a few sprinkles possible at the terminal through the
morning before Turnagain Arm winds move into the airport around
20Z. Southeasterly wind gusts 25-30 knots continue through the
afternoon before slowly diminishing through the evening hours, and
light northerly winds return to the terminal by midnight. VFR
conditions and light winds continue through Tuesday.

&&