676
FXAK68 PAFC 210002
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
402 PM AKDT Sat Jul 20 2024

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

A warm albeit relatively uncertain weather pattern will dominate
the forecast for the remainder of the weekend into early next
week. While most areas will stay dry, a few isolated thunderstorms
are expected Sunday afternoon and evening particularly in the
Susitna Valley and Copper River Basin, with lower confidence in
thunderstorm development across the western Kenai Peninsula and
Anchorage Hillside. High temperatures on Sunday will rise into the
70s for most, nearing 80 in the Copper River Basin and Susitna
Valley.

An energetic easterly shortwave rotating between a ridge over
mainland Alaska and an upper low over the Gulf will bring a period
of more widespread precipitation to portions of Southcentral
Alaska on Monday. Confidence has been quite low in regards to the
timing and potency of this system, but rain will likely begin to
overspread the southern Copper River Basin and Prince William
Sound region Monday afternoon, fully spreading into the Anchorage
Bowl, Mat Valley and western Kenai by Monday evening. Some weak
instability and clearing across the Susitna Valley and northern
Copper River Basin may promote thunderstorm development Monday
afternoon and evening. The heaviest precipitation will be fully
through the area by late Monday night, but a few lingering showers
are still possible Tuesday morning. Conditions by Tuesday
afternoon will be mostly dry with some breaks in the clouds
possible.

-ME

&&


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

Current satellite images show an occluded low centered over the
Western Aleutians and a ridge over Southwest Alaska and areas of
patchy fog on the Southwest and Aleutian coastlines. The low`s
occluded front is bringing clouds, wind, and rain to the Central
and Eastern Aleutians as Pacific Ocean moisture moves northward.
The front will dissipate Sunday as it moves eastward with the
building of a ridge over Southwest Alaska.

Periods of rain are expected into Sunday afternoon for the
Central Aleutians as the front slowly moves eastward resulting in
0.50" to 1.00" of total rain this weekend. Wind gusts across the
Alaska Peninsula will range from 30 to 40 mph, diminishing Sunday
afternoon. Scattered afternoon rain showers with isolated
thunderstorms may be possible over the Alaska Range on Sunday.


&&

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

An omega block will remain in place at the onset of the long term
forecast period. Ensemble guidance shows good agreement with an
upper low positioned over the western Bering and a second upper
low positioned over Southeast Alaska/British Columbia on
Wednesday. An area of high pressure will reside between these two
features with largely benign conditions expected across both
Southwest and Southcentral Alaska. Seasonably warm temperatures
and below normal precipitation chances will exist through
Thursday. By the end of the week the pattern begins to breakdown
with high pressure shifting into the Gulf of Alaska and a trough
deepening over the Bering. Deterministic models suggest the
passage of a stronger shortwave through the Western Alaska Range
and into Southcentral by the end of the week, which should spell
widespread precipitation chances for both Southwest and
Southcentral Alaska along as well as cooler temperatures. High
pressure then resumes over interior Alaska by Saturday with
precipitation chances decreasing.

-BL

&&

.AVIATION...

PANC...VFR conditions will persist. The only real question is
whether the Turnagain Arm wind will make it over the terminal this
evening or not. With the northerly pressure gradient over the
northern Inlet early this afternoon, the winds will be delayed
until early evening if they do develop. The reason to think they
will eventually move into the airport is that the pressure
gradient is expected to switch to the south-southwest this evening
and remain that way overnight and into Sunday. The Turnagain Arm
wind itself should ease off by late evening leaving a southerly
wind less than 10 kt overnight into Sunday.

&&


$$