704
FXAK68 PAFC 281301
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
501 AM AKDT Tue May 28 2024

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

An upper-level trough, embedded within the northeasterly flow
between an upper-level ridge over the Susitna Valley and a low
over the Gulf, is moving across the Copper River Basin this
morning. This feature is producing widespread rain from the
northern Copper River Basin south to Cordova. To the west,
conditions are drier; however, a southwesterly low-level flow
underneath the ridge, is keeping moisture in the form of low
cloud cover, in place from the Mat-Su Valleys south across Cook
Inlet.

The upper-level trough will be slow to dig southwest today. As it
does, a second wave moving east out of the southern Yukon will
meet up with it, helping to enhance shower activity across the
eastern and southern portions of the Copper River Basin later
this morning. These features will then move west overnight and
elongate across Southcentral through Wednesday evening as the
ridge retreats to the north. The result will be a westward
progression of the showers over the Chugach and Talkeetna
Mountains tonight and across Cook Inlet, the Anchorage Bowl, and
the Mat-Su Valley by early Wednesday morning. The precipitation
will then become more scattered through Wednesday as the waves
weaken and elongate across the region.

Farther west, a frontal system will move across the AKPen late
Tuesday, lifting toward Kodiak Island Wednesday morning. A coastal
ridge will develop ahead of the front, tightening the pressure
gradient along the coast and allowing southeasterly gap winds to
develop late Tuesday night through Wednesday. The gusty winds are
expected to peak late Wednesday with gusts up to 30 mph possible
along Turnagain Arm and across the Knik and Copper River Valleys.

The gusty winds are then expected to diminish Wednesday night as
the front near Kodiak Island slows and becomes more east/west
oriented, shifting the pressure gradient along the coast. The
southeasterly flow aloft will allow showers to persist along the
coastal mountains; however, the bulk of the steadier rainfall will
likely remain over the Northern Gulf along the front.

-TM

&&



.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3)...

Dry conditions are forecast to start the day off across Southwest
Alaska on Tuesday with temperatures to warm into the upper 50s
and lower 60s this afternoon. With that warming and the passage of
an easterly wave through the region comes renewed chances for
showers and thunderstorms later in the day. Forecast models are in
good agreement with the development of weak instability at the
lower elevations coinciding with peak daytime heating. Thus,
convective development appears likely, first over western portions
of Greater Bristol Bay, and then into the Kuskokwim Delta, in
concert with the northwestward movement of the easterly wave. By
Wednesday, a dissipating front along the Southwest Coast and
diffluence aloft associated with an upper low parked off the
coast, should result in increased cloudiness and areas of
scattered showers. A day of cooler conditions will prevail. Weak
high pressure over interior Alaska may temporarily nudge its way
into southwest on Thursday. Breaks in cloud cover could promote
another threat for isolated wet thunderstorms later in the day.

Across the Bering an upper low located over the Central and
Eastern Aleutians will maintain generally cloudiness and areas of
occasional showers for the Aleutians up into the Pribilofs. This
low will remain in place through Thursday before becoming sheared
apart by the next approaching low into the western Bering and an
eastward moving shortwave south of the Aleutian Chain. The western
Bering low will bring the next front, which is forecast to
gradually push eastward across the entire Aleutian Chain through
the weekend.

-BL

&&


.LONG TERM FORECAST (Days 4 through 7) Friday through Monday...

The weekend opens with a decaying upper level low over the
Northeast Pacific that gets absorbed by a Western Aleutian low as
it moves across the Alaska Peninsula by Sunday. This second low
tracks to the East-Southeast through Monday. A broad trough
remains over most of the Bering and Southern Alaska through the
forecast. Model agreement continues good, opening with a
deterministic blend and transitioning to a one-half ensemble means
by the beginning of the week. Most of the active weather
continues across the Southern portions of the state.

Southcentral Alaska stays under persistent Southeasterly flow,
keeping a good mix of moisture moving inland to the Alaska Range.
Showery precipitation will continue through the weekend. More
active lows, fronts or troughs brings periods of rainfall across
the Aleutians, Bering and AKPEN, and into Southwest Alaska.
Northerly windflow across the Western parts of the states keep
surface temperatures lower than normal. Only the Eastern Interior
will see any warmer temperatures, with a upper level ridge angled
over the Central and Northern areas.


-Kutz

&&
.AVIATION...

PANC...VFR conditions and light winds will persist through late
Tuesday evening. At that time, westerly winds will give way to an
increasing southeasterly Turnagain Arm wind that is expected to
move over the terminal by late Tuesday evening. These winds will
persist into Wednesday before slowly diminishing late Wednesday
evening. Gusts could approach 25 mph overnight tonight and up to
30 mph Wednesday afternoon and evening. Rain showers are also
expected to develop across Anchorage by early Tuesday morning,
potentially continuing through around noon. Occasional MVFR
conditions are possible with any shower activity.

&&


$$