323
FXAK68 PAFC 111346
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
546 AM AKDT Thu Jul 11 2024

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

An easterly wave moving across Southcentral has allowed for light
rain along the Alaska Range and hit or miss showers to develop
across Copper River Basin last evening and into the Susitna Valley
into this morning. These showers are expected to continue
throughout the day today and tonight. Higher chances for
precipitation will be along the coast and higher elevations.
Southerly gap winds through Copper River, and southeasterly winds
through Turnagain Arm and Knik River could be gusty to 30 mph in
the afternoon. This could help keep portions of the western Kenai,
Anchorage, the Copper River Basin, and Matanuska Valley,
relatively drier. Small craft, easterly winds will be likely along
the northern Gulf Coast near Kayak Island.

A break in the clouds inland and slightly decreasing chances of
rain will be brief tonight. Friday morning though, a front will
move into the western Gulf and Kodiak Island. Chances for rain
will increase substantially and spread east through Southcentral
Friday night. Probability of precipitation will increase across
Cook Inlet and Anchorage Friday evening and even more so for
Saturday morning as a low develops in the northwestern Gulf. As
the bulk of energy from the Bering low sinks into Bristol Bay,
additional vorticity in the upper levels pivots into southwesterly
flow and directing the energy up Cook Inlet. Depending on the
position of the surface low and orientation of the front, Copper
River Basin could see a chance of rain Saturday afternoon.
Associated QPF is expected to be higher with ample moisture
content in a more stratiform setup. Small craft winds along the
front will strength to gale force Saturday night as the front
becomes parallel to the coast. There is a high chance for small
craft winds to push into Prince William Sound Saturday. The
strength of the winds in the Sound will depend on the placement of
the surface low and the associated front. In the strongest model
solutions, gusts could be into storm for the coast from Montague
Island to Kayak Island. This could also mean gale force winds for
Prince William Sound. There will be gusty winds through Turnagain
Arm and Knik River Valley, but these area will also be affected by
the model uncertainty for Saturday. None the less, expect
rainfall to be more widespread Saturday and throughout the weekend
with slightly cooler temperatures and a continuation of gusty
winds at times.

rux

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (Wednesday through Saturday)...

A decaying frontal boundary continues to shift eastward out of
Southwest Alaska, diminishing the expected rainfall across the
area this morning into early this afternoon. However, the cool,
cloudy, and rainy pattern is expected to continue as a new front
extending from a surface low in the Bering Strait down to a
surface low over the Central Aleutians will push east into the
Southwest coastline by late tonight into early Friday morning. The
low over the Central Aleutians is being fed by a stream of sub-
tropical moisture, feeding into a warm front currently draped
from the western Aleutians eastward toward the eastern Aleutians.
The upper level jet steam, zonal in nature will continue to send
disturbances along this front through late week, which will
reinforce the existing upper low over the Bering Sea.

In sensible weather terms, continued cloudy and below average
temperatures are expected across the mainland as the system
remains in place. Along with the front Friday, gustier
southeasterly winds are expected, especially along the
Alaska/Aleutian Ranges. Rainfall has the potential to break daily
records, and combined with the last system, lead to rising water
levels on local streams, creeks and rivers. Overall, high
confidence in continued cloudy, cool, and rainy conditions.

CL

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Wednesday through
Saturday)...

The active weather pattern continues across the Bering Sea with a
frontal boundary draped from west to east across the Aleutians.
However, the front divides two very distinct air masses, cooler
and drier northerly flow across most of the Bering Sea behind the
previous cold front, and a much warmer/moister air mass across the
Aleutians. These conditions are ripe for widespread areas of fog
and low stratus along the warm front. Some areas will be locally
dense. Otherwise, periods of rain are expected through the week as
disturbances ride the front from west to east. Confidence is
higher than normal for increased precipitation across the
Aleutians and areas of fog.

MTL/CL

&&


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

A generally wet weather pattern remains over most of Southern
Alaska through the forecast period. Forecast model guidance is in
good agreement. There is a broad low stretching across the Bering
into the Western two-thirds of Mainland Alaska. A closed upper
level low near Nunivak Island weakens as it slips across Southwest
Alaska into the Gulf of Alaska for midweek. This low shows up in
a surface feature by Tuesday. Several upper level troughs rotate
through the pattern as well. The Eastern Interior holds onto a
weak upper ridge through the period, supporting surface thermal
troughing. Locally heavy rainfall is expected over Southwest
Alaska, most of the Alaska Peninsula and Kodiak Island, then
spreads across the Southcentral zones and inland to the Alaska
Range through Wednesday. A second surface low and front slide over
the Aleutians and Bering early Monday through Wednesday. A well
developed surface low queues up to the Western Aleutians for
Wednesday. Mostly showery precipitation is expected through the
region for the new week.


- Kutz

&&

.AVIATION...

PANC...VFR conditions will persist, with ceilings expected to
remain above 5000 ft. Gusty southeasterly Turnagain Arm winds will
pick up late morning/early afternoon before diminishing after
midnight. Vicinity showers are also expected in the afternoon,
with the potential for an isolated shower or two to move over the
terminal.

&&


$$