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000
FXAK68 PAFC 201324
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
524 AM AKDT Sat Apr 20 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Monday night)...

As of early this morning, a Flood Advisory remains in effect for
Kodiak City and surrounding areas while a Flood Watch remains in
effect for the remainder of Kodiak Island. While additional
rainfall is expected today, intensity will be much lighter than
what has been experienced the past three days. Thus, the threat
for further flooding impacts is diminishing and the expectation
is that these products will be expired at some point today. As
far as the latest rainfall totals, Kodiak Airport recorded 7.34
inches of rain Wednesday through Friday (April 17-19), which is
Kodiak`s 13th all time wettest 3-day total on record (*climate
records go back to September 1913).

While the overall large scale pattern remains the same, changes
are afoot. The low which has been spinning in the North Pacific
to the south of the Alaska Peninsula and Kodiak Island has
weakened and elongated. A short-wave at the base of the upper
trough continues to dig southeastward toward the Northwest CONUS,
with the long-wave trough taking on more of an E-W orientation
across the Northeast Pacific. The atmospheric river which has
been pumping moisture from the tropical Pacific up to Kodiak
Island is greatly weakened and about to be pinched off as the
short-wave trough nears the CONUS. Meanwhile, the blocking ridge
sitting to the north and east over Mainland Alaska and Northwest
Canada is beginning to retreat northward out of Southcentral. What
has been very strong winds at all levels between the trough and
ridge is finally beginning to weaken. At the surface, a weak
stationary front draped across Kodiak Island and the southern Gulf
is also weakening. Rain continues across much of Kodiak Island
and the northwest Gulf, but rainfall intensity has lightened up
significantly. Strong and gusty winds across the Kenai Peninsula
and northwestern Gulf coastal waters have diminished from their
peaks and continue to weaken this morning. Other than the winds,
weather is quiet over Southcentral. Temperatures have dropped well
below freezing over interior areas where clear skies prevail
while above freezing temperatures persist across the southern
tier of Southcentral due to high clouds and the aforementioned
winds.

The long-wave trough will continue to evolve over the next couple
days as the short-wave driving toward the Northwest CONUS breaks
off and exits across southern Canada and a newly consolidated
upper level low takes shape south of Kodiak. Today will be the
last day of steady (light) rain for Kodiak City and much of Kodiak
Island. As the new upper level low takes shape on Sunday, the
surface front will dissipate and a leading trough will lift
northward into southern Alaska. This will bring an end to rain for
Kodiak, with just a few light showers lingering in the region.
For Southcentral, expect one more dry and mostly sunny day today
with warm temperatures. The approach of the trough on Sunday will
lead to increasing clouds and showers, especially along the coast.

The forecast for Monday/Monday night is much more uncertain, as
models have really been struggling with consistency with track
of the upper level low. The latest runs seem to be consolidating
around the same general idea, in tracking the upper low into
Southwest Alaska Monday then back east or northeast toward
Southcentral Monday night as the upper level flow becomes more
progressive. However, the exact track and resultant area of
precipitation ahead of the low differs among the models and
from run-to-run. The end result for Southcentral will be
continued mostly cloudy skies with a chance of precipitation
through Monday night. With somewhat cooler air moving in aloft,
there is the potential that some of the precipitation Monday
night could fall in the form of snow.

-SEB

&&


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

A trough stretching from the North Pacific to the Bering Sea
will continue to bring rounds of precipitation through tomorrow
evening to Southwest Alaska and the Alaska Peninsula. The main
low south of the Alaska Peninsula that provided the region with
precipitation the past few days moves into the North Pacific. A
Bering low begins to move across the Aleutians tomorrow.

Today: A low moving northwestward through the Alaska Peninsula
and Bristol Bay this morning will bring mostly rain and high
elevation snow to the area through this afternoon. Its current
track is similar to yesterday`s resulting in continued north to
northwesterly wind direction and all snow for the Pribilofs and
Dutch Harbor. Persistent southeast winds from the aforementioned
trough will bring another chance of rain to the Alaska Peninsula
and portions of Southwest Alaska from late this afternoon into
the evening hours. After a short dry period, another round of
precipitation will return for this area again tomorrow afternoon.

This evening through Monday night: A ridge builds into the
western Aleutians late this evening but weakens as it moves
eastward. In its wake, a Bering low moves south and east remaining
north of the Aleutians. A shift to southwesterly warm gale force
winds will signal the arrival of its front on Monday evening as
it moves eastward. Rain will be the main precipitation type.

-DJ

&&

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

A pattern shift is expected as we go into the weekend with the
synoptic pattern breaking down. Sunday into Monday, a strong low
develops as it moves into the western Bering Sea that will track a
front eastward next week. While the pattern is expected to break
down leading into the long term forecast, high pressure will
remain somewhat stubborn over Canada and stretching into the
interior of mainland Alaska. The strength and placement of the
ridge will influence the direction of the upstream flow. Expect
unsettled weather to continue through next week. Periods of rain
spread across Southcentral Alaska through Wednesday from the Kenai
Peninsula to the Canadian Border.

Additional subtropical moisture will be drawn into the developing
western Aleutian low early next week. Heavy precipitation will
spread across the Aleutians beginning as rain and transitioning
to snow. Cold air wrapping into the low will help reinforce the
potential for Storm force winds. The influence of the front
appears to stretch into the northern Bering, affecting the
Pribilof Islands and St. Matthew Island.

Potentially heavy rainfall continues to spread into the Alaska
Peninsula with the front through Tuesday, and into Southwest
Alaska late Tuesday and Wednesday. Another round of rain then
moves to Kodiak Island late Tuesday through Thursday. Gusty,
southeasterly winds move through the Barren Islands into Kamishak
Bay Wednesday and Thursday. Some of the moisture could be
diverted south depending on the interior ridge, but heavy
precipitation remains possible and the amounts will depend on
whether there is additional support from a secondary trough
phasing with the front. Model agreement also breaks down towards
the end of the week.

rux

$$

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

$$