207
FXAK68 PAFC 050151
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
551 PM AKDT Thu Jul 4 2024

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

Our first wave of anticipated precipitation is currently starting
in the northern parts of the forecast area, specifically near the
Alaska Range and Talkeetna Mountains. The frontal boundary will
continue to move eastward overnight before dissipating by Friday
morning. With westerly flow aloft persisting through tomorrow,
dry air will help keep rainfall rates light for most places. The
exceptions to this will be near the Talkeetnas and northern
Susitna Valley that will get steadier rainfall rates. In contrast,
the placement and strength of the front will result in the western
Kenai Peninsula and Copper River Basin likely not seeing any
rainfall.

A break in rainfall for the region is expected during the daytime
hours on Friday as weak ridging tries to build in over
Southcentral. Gap winds along Turnagain Arm, Knik River Valley,
and the Copper River Basin will steadily increase ahead of a deep
upper level low digging into western mainland Alaska Friday night.
While most areas west of Prince William Sound will be dry,
widespread cloud cover will continue throughout the day.

The next and more intense round of precipitation will begin to
take shape by Saturday morning as a convergence band between the
upper low in northwest Alaska and the ridge in the Gulf of Alaska
starts to form. While most locations across Southcentral will get
periods of heavier rainfall, model guidance is still struggling on
the placement of the convergence band over the region. Most
guidance is suggesting the band will form along the gulf coast,
impacting the Kenai Mountains and Prince William Sound the most.
However, some models are depicting a more northerly solution,
placing the boundary on top of Cook Inlet and pushing it towards
the Mat-Su. The heaviest rainfall will start to diminish on
Sunday as the system begins to weaken and shift eastward,
resulting in slightly calmer conditions by the end of the weekend.

-BS

&&


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

Widespread showers continue across Southwest Alaska this
afternoon aided by a front tracking eastward from the Bering Sea.
After tapering off slightly on Friday, wetting rains are expected
to pick up again Saturday. High pressure over portions of the
Bering Sea, will continue to bring areas of patchy fog to the
Central/Western Aleutians and the Pribilof Islands.

&&


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

An elongated upper level trough with several low centers rotating
through the pattern on the Alaska Weather Map. The Arctic centers
slide Westward before dipping into the Bering, forming a broad
low across the Central Bering for midweek. This brings cooler
temperatures across the Bering and Western Alaska. The change
should help reduce the fire danger over large portions of the
Mainland. A number of shortwaves pass through the pattern through
midweek, spreading locally moderate precipitation across from the
Central Aleutians into Southwest Alaska and the Alaska Peninsula.
A second low center moving up from the Eastern North Pacific
merges with this low by Thursday. This low helps pump additional
moisture and precipitation across all of Southcentral Alaska and
across Kodiak Island and up to the Alaska Range through Thursday.
An upper level ridge establishes itself over the Eastern Interior
by the end of the forecast. Models across the Alaska Region remain
reasonably clustered, favoring the GFS/ECMWF blend through the
end of the forecast period.


- Kutz


.AVIATION...

PANC...VFR conditions and light winds persist through early
afternoon. Westerly winds then begin to shift, becoming more
southerly, by early evening as Turnagain Arm winds strengthen
ahead of an approaching front. Southerly to southeasterly winds
will increase, with sustained winds of 10 to 15 kt and gusts
approaching 20-25 kt. These winds will persist through the
overnight hours before diminishing slightly Friday morning.
Southeasterly winds will then increase again for Friday afternoon
and evening, with gusts of 25-30 kt by Friday night.

Light rain is expected late Thursday afternoon through Friday
morning, with minor uncertainty in timing. Any rain is expected to
be very light. Ceilings will drop with this rainfall, likely
below 5000 ft, with some guidance dropping ceilings to MVFR by
early Friday morning.

&&


$$