137
FXAK68 PAFC 031319
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
519 AM AKDT Thu Apr 3 2025

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

A warm morning is underway across much of Southcentral Alaska. A
rather thick upper-level cloud deck kept temperatures above freezing
across much of the road system as of 5am, with some locations even
remaining above 40. The rather impressive upper-level ridge that`s
been in place across Southcentral will gradually shift east over the
next couple days, allowing a strengthening storm-force low to move
into the North Pacific. The associated frontal system with this low
will start to bring rain (/high elevation snow) to Kodiak Island as
early as this evening before moving north into the Kenai Peninsula
overnight as it stalls out. The vast majority of impacts from this
storm will be along the coastal zone, with strong easterly winds and
rain. Snow levels will remain fairly high, starting out at around
1000 to 1500 feet early Friday morning, then rising 1800 to 2500
feet by late Friday. Thus, snow should not be a big issue along the
road system. Inland areas will remain mostly dry with strong
downsloping flow, though there could be an occasional brief period
of light precipitation as weak upper short-waves track inland.
Temperatures will remain above normal, with a trend toward above
freezing night-time temperatures due to extensive cloud cover.

-Brown/SEB

&&


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

...Key Messages...

 1) A Winter Storm Warning is in effect from 7AM Thursday to 4PM
    AKDT Friday for the Eastern Aleutians.

 2) A Blizzard Warning is in effect from 10PM Thursday to 7PM
    AKDT Friday for the Kuskokwim Delta Coast and Nunivak Island.


The forecast is mostly on track for our late season, moderate to
high end impact winter storm for the Eastern Aleutians and points
northeastward to the Kuskokwim Coast and Nunivak Island through
the short term.

Currently, an upper level low centered across the Southern Bering
is aligning well with a secondary upper low associated with a
nearly occluded North Pacific low that is almost stationary 450
miles SSE of Unalaska. This has formed an intense deformation band
of rain and snow for areas such as Nikolski and Unalaska. Some of
this moisture is spreading northward as the precipitation on its
northwestern flank pivots more so to the north and west ahead of
the low`s front paralleling the Aleutian Chain. A broad ridge of
high pressure situated over Shemya and the deepening low located
south of the Island Chain has resulted in a large pressure
gradient across this stretch of the Eastern Aleutians. In
combination with cold air advection on the backside of the surface
low, widespread gales and storm force wind gusts are impacting
the Eastern Aleutians, which is resulting in significant gap wind
gusts of 45-55+ kts through mountainous areas near Unalaska and
Akutan. Conditions should deteriorate throughout the day today and
into Friday as rain quickly changes to heavy wet snow for these
locales. Accumulations of 10-18" of snow with winds gusting
upwards of 60 mph is likely for these areas by midday Friday to
Friday afternoon, with localized areas of 20"+ not out of the
realm of possibility. On the other hand, a robust southerly to
southeasterly flow will keep temperatures elevated into the upper
30s to lower 40s for Sand Point eastbound, making this primarily a
rain event for the AK Pen and Southwest.


Snowfall also begins to spread northward by late Thursday to early
Friday, and conditions quickly start to go downhill for Nunivak
Island and the Kuskokwim Delta coast, including areas such as
Kipnuk, Mekoryuk, and Toksook Bay. As snow begins to fill in and
winds increase into Friday morning, blizzard conditions are likely
for these areas, especially Nunivak Island. Nunivak Island is
somewhat unique in this setup due to 80%+ coverage of sea ice.
Instead of frictional drag effects on wind with choppy seas,
friction will be negligible as it blows across the ice, and will
therefore prevent the wind from slowing down. Therefore, Nunivak
Island has the best chance of seeing blizzard and whiteout
conditions from this storm, but these conditions are still
expected to be felt inland along the Kuskokwim coast. These
conditions will persist throughout the day on Friday and finally
slowly begin to wind down on Saturday morning, perhaps lingering
into Sunday. However, there still may be reduced visibility from
blowing snow across Nunivak Island at this time, so a downgrade
from the Blizzard Warning may be needed for these timestamps for
less impactful weather. These regions within the Blizzard Warning
are on pace to see 5-9"+ of snow with winds gusting upwards of 40
mph.


For the Pribilof Islands, blowing snow due to strong winds could
reduce visibility down to a quarter to half mile at times from
Friday afternoon lasting into Saturday afternoon. There is still
some uncertainty with the models on just how far the edge of the
aforementioned band of snow pushes westward, so snowfall totals
are more in question than blowing snow potential due to a strong
30-40kt fetch of northerly winds forecast to affect the Islands.
Even with lesser amounts of snow than other areas, light snowfall
accumulations with strong winds can still create blowing snow
conditions. As of now, the model consensus suggests 1-3" of
snowfall for the Pribilof Islands by Saturday afternoon, with the
eastern most part of the Islands being on the higher end of that
range.

-AM

&&


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

The most significant feature on the Alaska Weather map is an
elongated trough stretching from the Arctic through Interior
Alaska to the Gulf of Alaska through the forecast period. Closed
lows over Northern Alaska and the Gulf weaken through midweek.
Although there is some oscillation within the elongated trough,
there is little movement. Ridges over the Western Canadian
Provinces and the Bering also weaken through the period. Forecast
continuity remains good with a GFS / ECMWF / Canadian blend, but
minor differences with shortwaves gliding through the pattern
represent the variations and short term changes in forecast.

A moderately strong surface low over the Southern Gulf of Alaska
spreads locally heavy rainfall from the Eastern Aleutians over the
Alaska Peninsula through Monday. Gusty winds over the AKPEN
linger through midweek. Locally heavy rains marches across Kodiak
Island and the rest of Southcentral Coastal zones through
Wednesday. Areas of locally moderate snow spread over Southwest
Alaska into the Interior, and diminish through midweek. A well
developed low and front approaches the Western Aleutians for
Sunday, but dissipates to the South of the chain by Tuesday.

- Kutz

&&

.AVIATION...

PANC...VFR conditions and light winds will generally persist
through the morning. Gusty winds out of the Turnagain Arm may bend
back over ANC for a period this afternoon into the evening before
turning back down-inlet in response to an approaching frontal
system.

&&


$$