985
FXAK68 PAFC 022329
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
329 PM AKDT Thu May 2 2024

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

A large upper-level low continues to slowly push eastward across
the Gulf of Alaska and far northeast Pacific Ocean. Multiple
surface lows along a front continue to draw North Pacific moisture
northward into Kodiak Island and the eastern Kenai Peninsula.
Typical downsloping areas of the western Kenai on northward are
remaining dry with strong low/mid-level southeast flow.
Precipitation will taper off this evening as the parent low
weakens, with just some light upslope precipitation remaining.

Another low complex over the Bering and associated front will
then quickly move into the region in place of the existing system
on Friday into the weekend. Precipitation will pick back up for
Kodiak and the coastal Kenai Range, also pushing into the Prince
William Sound region. Downsloping will continue for the western
Kenai up through the Anchorage Bowl and Mat-Su Valley, keeping
conditions dry but cloudy. High temperatures for at the least the
next several days will be near climatological averages, with highs
in the 50s for most of the region.

-ME

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIAN
ISLANDS (Days 1 through 3: This afternoon through Sunday afternoon)...

Some shifts in the forecast, but the general picture remains
largely unchanged. Active weather continues through the weekend
as a 973 mb low near Attu Island and its front move across the
region. Here are the primary hazards we`re monitoring:

* A Flood Watch for an ice jam is in effect through Saturday
  morning for Aniak.
* Periods of light to moderate rain (with snow possible for
  Pribilof Islands) and gusty winds as the front moves through on
  Friday.
* Colder temperatures and light freezing spray extend across the
  Eastern Bering/Southwest Alaska coastline from late Saturday
  through early next week.

Diving into the details... satellite imagery shows two storm
systems impacting Southern Alaska: a weakening 998 mb low in the
Gulf of Alaska, and a 973 mb low currently near Attu Island. With
the Gulf low continuing to weaken and exit out of the area, fairly
benign weather is expected for Southwest Alaska through the
remainder of today. Expect isolated to scattered showers this
afternoon and evening, with gusty southeasterly winds gradually
diminishing. Further west, the low near Attu is beginning to
occlude. With the front moving out of the area, expect generally
improving conditions for the Western and Central Aleutians.

However, by early Friday morning, a vigorous upper level
shortwave rotating around the parent low will aid in the
development of a new surface low along the triple point of the
front. As the new low develops near the Eastern Aleutians, it will
tap into a stream of tropical moisture. Forecast precipitation
amounts and wind speeds have been increased for the Eastern
Aleutians and Alaska Peninsula as the low looks to be a bit more
robust than initially expected. This moisture will also make its
way across Southwest Alaska through Friday, leading to a wet end
to the workweek for much of the area. Even the Western and Central
Aleutians will see precipitation on Friday, though to a lesser
extent as showers move around the occluding parent low. Forecast
confidence is quite good with this well-defined system. The
biggest question will be snow amounts for the Pribilof Islands;
with temperatures hovering just above freezing, there is
uncertainty regarding how much precipitation will fall as snow
versus rain. The current forecast is for a paltry 1-3 inches,
which may even be a bit high as it relies on precipitation
staying mostly snow.

From Saturday through Sunday, the triple point low will occlude as
it moves over Southwest Alaska. At the same time, an upper low
moving into the Bering Sea from the Arctic will bring shot of
cold air. Expect rain showers to slowly diminish in coverage
through the weekend, with the potential for some snow showers late
at night/early in the morning as temperatures reach their daily
minimum. Otherwise, daytime heating should keep precipitation as
mostly rain. The other hazard to monitor will be the return of
light freezing spray along the northern and eastern Bering Sea
beginning Saturday night. This will be supported by colder air
moving in aloft, northerly winds at small craft speed, and sea
surface temperatures just below freezing. It may be May, but
winter seems not quite ready to let go of its grip over the state.

-KC

&&


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

The broad upper level Bering Sea trough harboring a closed low
near St Lawrence Island will be breaking down and moving through
the Gulf of Alaska into the Eastern North Pacific by the end of
the forecast period. Forecast models demonstrate less confidence
in the changing weather pattern through the week. The occasional
injection of North Pacific energy and some jetstream support helps
bring some significant weather producers across the Aleutians. It
also helps draw the Bering low Southward beginning Tuesday. The
system forms across the Central Aleutians and continues over the
Alaska Peninsula for Thursday. An Eastern Gulf low weakens and
moves into the Canadian Provinces as a trough by Wednesday. The
upper level ridge weakens but holds on over the Arctic Coast.

Widespread precipitation will be the order of the day across the
Western and Central Aleutians for Tuesday, and the Eastern
Aleutians, AKPEN, and the rest of Southern Alaska to the Canadian
Border through the forecast. Additional rainfall should not be a
factor with Interior Rivers dealing with ice jams and flooding due
to above average snow melt. Locally heaviest rainfall is expected
to spread from the Eastern Aleutians, AKPEN, parts of Cook Inlet,
Kodiak Island, the Eastern Kenai Peninsula and over Prince
William Sound for Wednesday and Thursday. The precipitation area
continues to spread Eastward along the Gulf through the Weekend.

-Kutz

&&

.AVIATION...

PANC...VFR conditions will persist. Winds will once again be the
main question as the southeasterly Turnagain Arm wind, through
not as strong as it often is, looks like it will just make it up
to the airport for this afternoon and evening. However, there is a
chance that it does not and winds will remain from the west-to-
northwest. The stronger east-to-southeast winds aloft will likely
not make it as low as 2000 ft for true low level wind shear, but
there may be some wind shear above the 2000 ft level through
Friday.

&&


$$