Area Forecast Discussion
Issued by NWS Anchorage, AK

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403
FXAK68 PAFC 251248
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
448 AM AKDT Thu Jul 25 2024

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

The upper level low/trough that helped focus showers and a few
thunderstorms near the Talkeetnas and northern Alaska Range last
evening into the overnight has now drifted off into the northern
end of the Copper Basin, with a few showers still drifting around
it this morning. Elsewhere, an upper level ridge is momentarily
building back into place across the Gulf and much of Southcentral.
Except near the aforementioned low, widespread low stratus trapped
under the ridging aloft has enveloped much of the region. This
could lift/clear to an extent by this afternoon over more interior
land areas, but overall expect a cloudy day for all but the
mountain peaks. The one exception will again be the Copper Basin,
which is set to enjoy one final day in the 70s. A couple
thunderstorms again will be possible this afternoon near the
Alaska Range, mainly close to Mentasta Lake and the Wrangells.

By this evening into tonight, a frontal system associated with a
deep upper trough moving into Southwest Alaska will move up past
Kodiak Island and up into the Kenai Peninsula as the longwave
ridge begins to move off into Northwest Canada. An onshore
coastal pressure gradient will sharpen out ahead of this front,
driving gap winds that will pick up through the Turnagain Arm,
Knik Valley and Copper River Basin starting tonight and persisting
into Friday. Rain tied to the leading frontal feature will first
shift from Kodiak into the Kenai Peninsula, but may hold off a
while longer tonight across the western Kenai Peninsula out to
Anchorage and the Mat Valley due to just enough drying cross-
barrier flow in the low levels. However, by early Friday morning,
the entire upper level trough will approach the Cook Inlet region
from the west, shifting much stronger dynamic forcing into place
that will quickly overcome any downslope drying. Widespread light
to moderate rain will spread northeast as the upper trough
advances in the same direction throughout the day on Friday.
Rainfall totals will range from 0.5 to 2 inches in general, with
the highest amounts focused where flow upslopes into terrain on
the north side of Prince William Sound and the northern Susitna
Valley.

From Friday night into Saturday morning, rain will taper off for
about the western half of the outlook area as the main trough
shifts into the Copper Basin and as moist southwest flow becomes
more westerly and drier. Rain near the trough will persist for
longer into Saturday across the Copper Basin, though this should
finally taper off as well as this feature exits into the Yukon
Saturday afternoon.

AS

&&


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

Thunderstorm activity diminishes for the remainder of this week as
a front pushes inland and atmospheric stability increases. A more
fall-like pattern moves in with rain beginning over the coast
this morning, becoming more widespread over the rest of Southwest
by this afternoon. Temperatures are expected to drops closer to
normal, ranging from the upper 50s to upper 60s with some isolated
areas in the Kuskokwim Valley pushing low 70s. The Aleutians will
have a brief reprieve from the bombardment of rain showers today
before the next system tracks over the Western Aleutians early
Friday morning. The associated front will move eastward across the
Chain through Saturday.

&&


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

An active pattern is expected to persist throughout the period. A
shortwave over the Bering embedded within the main longwave
trough axis will move over Southwest Alaska late on Sunday.
Widespread moderate to locally heavy rain is possible over
Southwest Alaska by Sunday afternoon, with the system spreading
eastward into Southcentral Alaska during the day Monday. Unsettled
conditions with periods of showers are expected to persist for
Southern Alaska on both Tuesday and Wednesday as the now upper
level low remains situated over mainland Alaska. Gusty
northwesterly gap winds are possible across the Alaska Peninsula
on Tuesday as the low departs to the east over the Northern Gulf
and a weak transient surface high builds in over the central
Aleutians. Another system emerges from the North Pacific and
impacts the Aleutians with periods of rain on Wednesday. Overall,
temperatures will remain below average for the long term period
with persistent cloud cover and rain.

-ME

&&

.AVIATION...

PANC...Low clouds and patchy fog are possible through this
afternoon. A front bringing scattered rain showers and southerly
to southeasterly winds could periods of MVFR conditions this
evening and continuing through Friday evening.

-DJ

&&

$$