Bethel, Alaska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

451
FXAK68 PAFC 231439
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
539 AM AKST Mon Dec 23 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Christmas Day)...

Another day, another low tracking out of the Gulf and westward
across Kodiak Island. The front associated with this low extends
over Cook Inlet and then bends eastward into the Copper River
Basin early this morning. This front is bringing more rain to
coastal areas, but once again mostly downsloping out the
precipitation on the lee side of the mountains. The area that is
expected to see the biggest impact is in the southern Copper River
Basin to Thompson Pass where there remains the potential for
freezing rain along the Richardson Highway today. Freezing levels
for the entire Kenai Peninsula are above highway levels so all
precipitation along the Seward and Sterling highways is expected
to be rain today. One question that remains for the forecast late
this afternoon through the overnight hours is whether or not the
Turnagain Arm winds will makes it into the Anchorage Bowl or if
they remain bending southward down Cook Inlet. Even a brief
arrival of Turnagain Arm winds would jump temperatures in
Anchorage from highs in the mid 30s into the lower 40s, even if
they were brief. At this time it looks more likely that these
winds will remain turning south out of Turnagain Arm and keep more
northerly surface winds in Anchorage so temperatures in the
forecast reflect that expectation.

For tomorrow, there is a little difference with the front that
will move into Southcentral in that it is originating from a low
the will be along the Aleutians instead of tracking from
southeast-to-northwest across the Gulf like the lows have this
past week or more. That will allow colder air aloft to wrap into
the system as it occludes and should help to switch much of the
precipitation for inland areas to snow from the rain and freezing
rain combo of the past number of days.

As one gets to Christmas Day on Wednesday, there does creep in a
significant amount of uncertainty again as a triple point low is
expected to develop along Tuesday`s front in the eastern Gulf.
Models are once again widely divergent on how to handle this low
once it does develop.

&&


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

Two main areas of active conditions are present this morning at
nearly opposite ends of the outlook area. The first is related to
an elongated trough extending from a low now slowly approaching
Kodiak Island. Bands of mixed precipitation continue to affect
mainly parts of Bristol Bay, where a mix of snow and freezing rain
has been observed across several parts of the region at times from
yesterday evening to early this morning. While a layer of warm air
aloft melting falling snow higher in the atmosphere remains in
place, this layer will cool off below freezing as the day
progresses, allowing freezing rain to switch over to predominantly
snow where surface temperatures remain below freezing. Out to the
west, a storm force front associated with a 945 mb North Pacific
low is now reaching the far western Aleutian Chain as moderate
rain and strong easterly winds spread into the region.

By this afternoon, the aforementioned frontal boundary will
continue northeast into the central and eastern portions of the
Aleutian Chain as it weakens to gale force. A new low is expected
to form along the boundary somewhere immediately south of the
eastern Aleutians or southern AKPen, and this new low will track
generally north into the far eastern Bering during the day on
Tuesday. Meanwhile, the remnants of the Gulf low will lift north
as an open wave trough into Southwest from tonight into Tuesday,
spreading light snow north and west as it moves across.

By Tuesday evening, the eastern Bering low will stall out
somewhere near the southern AKPen and continue to focus areas of
rain and snow across parts of the region as it meanders in place
through Wednesday. Farther west, a much colder air mass
originating in the Arctic will spill down into the central and
western Bering from Tuesday to Wednesday, helping to kick off
numerous convective snow showers that will spread south into the
Aleutians and Pribilofs as the air mas moves over the
comparatively warm sea surface and becomes unstable. Heavy
freezing spray will develop with northerly gales flowing away from
the ice edge, though sea surface temperatures appear to be a bit
too warm (around 3 to 4 Celsius) for a more widespread freezing
spray event with this particular cold air outbreak.

-AS

&&

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

A broad upper level trough stretches from the Arctic all the way
down to the North Pacific and northern Gulf on Wednesday, with
several surface lows forming in the pattern. The trough axis will
shift eastward into the weekend, with the main cluster of surface
lows taking shape in the central Gulf. A ridge will start moving
into the western Bering late Thursday before moving over mainland
Alaska by late Saturday. Behind the ridge will be a second upper
level trough moving in from Kamchatka over the western Aleutians
and Bering by Saturday. The Bering ridge and a ridge forming over
Southeast Alaska will interact over the interior on Sunday,
resulting in a strong ridging pattern over most of mainland Alaska
by the end of the extended forecast period.

While the troughing pattern persists through Saturday, the series
of lows and fronts forming near the Alaska Peninsula, eastern
Aleutians, and Kodiak will help provide repeated rounds of heavy
rains along the coastline until the ridge builds in. Bitter cold
air will begin to fill in over interior Southwest Saturday before
spreading into portions of Southcentral on Sunday, continuing
beyond the end of the extended forecast period.

&&.AVIATION...

PANC...VFR conditions to persist. A weakening trough over the
western Gulf will move into Southwest Alaska through the course of
the day. LLWS will be present into the afternoon hours with light
N`ly surface winds and gusty SE`ly winds at around 1500`. Some
uncertainty exists to whether Turnagain Arm winds bend into the
terminal later today and tonight. However, the pressure gradient
will likely not be strong enough due to the weakened state of the
passing trough.

&&


$$