999
FXAK68 PAFC 181326
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
526 AM AKDT Tue Jun 18 2024

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

The upper level ridge that has been over the Gulf of Alaska and
Southcentral is starting to edge eastward as a front is pushing
northward toward the southwest Gulf. This is the start of a
pattern shift with the unstable airmass that has been over
Southcentral being pushed farther northward with the Copper River
Basin being left as the only area with much convective potential
this afternoon and evening. The Marine stratus that pushed up Cook
Inlet Sunday afternoon into Monday has largely dissipated as the
ridge moved eastward. there is still some patchy fog around, but
this should dissipate as the day warms. Where the stratus has not
dissipated in over the Gulf and Prince William Sound. The
subsidence from the ridge and persistent southwest flow onto the
coast will make it difficult for this stratus to clear out until
Wednesday of even Thursday. Therefore expecting from Seward to
Valdez to Cordova to remain under this marine stratus through
tonight. It is possible for there to be a break this afternoon or
evening, but it should return shortly with this pattern.

By Thursday, the pattern will have shifted enough to have cleared
out the low clouds, but with southeast flow aloft, more general
cloudiness is expected over Southcentral for the end of the week.

&&


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


Satellite shows the main low pressure rotating south of Adak will
continue to bring waves of energy to the Southwest through
tomorrow afternoon. South to southeasterly wind flow will continue
to bring rain showers from the Central Aleutians to inland areas
of the Southwest into this evening as a secondary low pressure
migrating south of Sand Point moves into the Bering Sea later
today. Radar shows the area of heaviest rain showers over the
Alaska Peninsula/Eastern Aleutians where this secondary low
continues to enhance precipitation through late this morning.
Though the chance of thunderstorm and lightning activity
experienced the past few days is below 5% region wide, an isolated
late afternoon to mid- evening thunderstorm is possible from
Sleetmute to Aniak today. Gap winds in the Alaska Peninsula
ranging from 15 to 25 knots are expected this afternoon into the
evening hours.

The aforementioned main low will move over the Central Aleutians
late tomorrow morning resulting in a brief period of light
rainfall for the Central Aleutians. Southerly to southeasterly
flow persists during this time though for the Eastern Aleutians,
the Alaska Peninsula and most of the Southwest keeping the chance
of widespread scattered rain showers and cooler temperatures
over the area.  Widespread isolated rain showers are expected
Thursday region wide.


-DJ

&&

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

Model agreement is pretty good until around Sunday and the GFS
becomes the outlier. For Friday, mainland Alaska will be separated
by low pressure over the Gulf and high pressure to the north. Any
easterly waves coupled with instability over the mainland could
lead to chances for convection. A progressive ridge over the
Bering Sea will be moving towards Southwest Alaska where low
stratus and fog will be possible. Farther west is a North Pacific
low with a front transecting the Western Aleutians. Precipitation
will accompany primarily small craft winds are expected. Gusts
could approach gales, but are not expected at this time. By
Saturday, the ridge will have moved across mainland Alaska and
overall flow appears weaker, but the slight chances for showers
will linger, especially over higher terrain and thunderstorms
appear less likely for the weekend. Sunnier and drier weather is
possible for the upcoming weekend though. Over the Aleutians, the
low will move along the Aleutian Chain with the front reaching the
Pribilof and the Eastern Aleutians. Model agreement falls apart
later Sunday through Monday. GFS is highlighting a vigorous low
into the Bering Sea, though the representative forecast is leaning
towards a more mild weather with weak lows and more progressive
flow that is similar to what has been occurring more recently.

&&

.AVIATION...

PANC...Some ares of stratus are still lurking around Cook Inlet
early this morning. There might be a short period of MVFR ceilings
in this stratus this morning, but it looks increasing likely that
it should clear out by late morning. Therefore VFR conditions are
expected form late this morning through tomorrow.

&&


$$