488
FXAK68 PAFC 190018
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
418 PM AKDT Thu Jul 18 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
This afternoon through Sunday evening)...

A potent upper-level low has been stubborn to move further
southward today. This slower movement has thus resulted in a
longer duration of light rain across the area. This low, however,
will continue southward through tonight and Friday towards Kodiak
Island. Rain showers over mainland Southcentral will taper off
this evening and tonight. Light rain will persist over Kodiak
Island through Friday before tapering off Friday evening.

Meanwhile, there will be a warming and drying trend for mainland
Southcentral Friday and through the weekend, especially for the
interior locations. There is still some uncertainty for Saturday
with regards to the ultimate track of a lobe of low pressure that
breaks off of the parent low in the North Pacific. Generally, the
best chances for precipitation Saturday appear to be along the
northern Gulf coast and perhaps the eastern Kenai Peninsula.

Further inland, an easterly wave moving over the Copper River
Basin and westward from there could help spark off a chance of
isolated thunderstorms Saturday afternoon for there, the Susitna
Valley in the early evening, and perhaps the Matanuska Valley
before this activity tapers off late Saturday evening. There is
also uncertainty with this easterly wave. The NAM model is very
aggressive with persisting the wave through Anchorage and the
Kenai Peninsula through most of Sunday. However, other guidance
does not show this particular solution and the forecast also does
not reflect this solution. Regardless, the Copper River Basin and
perhaps the Susitna Valley has another chance for isolated
thunderstorms Sunday afternoon with instability building in
association with day-time heating.

&&


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

A pattern change is under way as a ridge of high pressure
builds across the Aleutian Islands and Bering Sea towards
Southwest Alaska. Generally, expect a warming and drying trend for
Southwest Alaska under the ridge. For the Western Aleutian
Islands and Bering Sea, wetter and windier conditions are on tap
as a low moves in today and lingers through Saturday.

This afternoon a robust upper level low is over the Alaska Range
moving south towards the Alaska Peninsula. Model guidance has been
hinting at convective rain showers, but this activity should be
limited to higher terrain.

In the Bering Sea and Aleutian Islands, inbound warm, moist air
accompanying the low provides a favorable environment for low
stratus and fog development. As such, the forecast includes
widespread areas of fog through Thursday night. Visibility could
be one-quarter mile or less in some areas, but uncertainty
remains on the strength of the inversion for fog to be that dense.
In addition, warmer, summertime sea surface temperatures mean
that near-surface air temperatures may not be cool enough for a
strong inversion to develop. As such, forecast visibility is 1
mile or greater for now.


&&


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

An omega pattern will dominate the long-term period, with large
upper-level lows situated in the Bering Sea and the North Pacific
near the Gulf. Between these lows, a high pressure ridge will
situate itself over Southwest Alaska. This setup will keep the
Bering Sea, Aleutian Chain, and southern Alaska Peninsula active
due to numerous shortwaves rotating around the Bering low. The
ridge, initially over Southwest Alaska Saturday and early Sunday,
will shift eastward toward Southcentral Alaska while weakening. A
frontal system will be approaching Southwest Alaska by Monday
morning, with locally heavy rainfall possible. Confidence remains
relatively low in the front`s ability to bring precipitation
inland, but the coast is most likely to see rain. Showery and
unsettled conditions are expected across Southwest Alaska through
midweek as more shortwaves pass through the Bering.

For Southcentral Alaska, the North Pacific/Gulf low will pull
easterly waves from the Yukon into the region. This pattern will
be favorable for precipitation in the Copper River Basin and the
Susitna Valley. Through Wednesday, the upper-level ridge will
begin shifting steadily eastward towards the Yukon. This will
allow for surface low pressure and other features to push into the
area, spreading the rainfall expectancy across much on mainland
Southcentral.

&&

.AVIATION...

PANC...Rain showers diminish through this evening as a low drops
southwards towards the southern Cook Inlet. MVFR ceilings may
bounce between IFR and MVFR this afternoon with VFR ceilings
returning by early Friday morning.

CCC

&&


$$