Sterling, Alaska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

304
FXAK68 PAFC 231333
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
433 AM AKST Sat Nov 23 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3: Saturday through Monday night)...

Conditions are very much status quo over Southcentral Alaska this
morning as the blocking ridge remains the dominant feature across
the region. This feature, however, has shifted southward, allowing
high cirrus clouds from a storm system over the western Bering to
spill over top the ridge and over the western half of the Southern
Mainland.

The flow aloft has also diminished overnight, allowing
temperatures at the top of the inversion to cool slightly, with
overnight lows remaining near or just above freezing. Nearer the
surface, temperatures have again fallen from the teens above zero
for locations near the coast and away from the gap winds to the
teens below zero in the Copper River Basin. An area of fog has
also developed over Knik Arm overnight and is moving over
Anchorage this morning. A dense fog advisory is in effect through
this morning.

The gap winds, with gusts to 40 mph for Whittier and Seward, will
begin to wind down this afternoon as the surface ridge over the
interior weakens and shifts slightly east and the upper level
ridge moving south allows for the development of a trough over
the northwestern Gulf of Alaska. This trough will shift the winds
both at the surface and the lowest third of the atmosphere from
north to south, breaking down the gradient-driven gap winds. These
winds may also bring low clouds currently over the southern Gulf
to the immediate coast by Sunday morning.

With the inversion slowly weakening, warmer temperatures aloft
over the mountains will continue to trend downward, falling to
near freezing Sunday afternoon. Additionally, inland valleys
could see a slight warm up from bitter cold temperatures, though
staying below freezing. How cold overnight low temperatures fall
Sunday morning across interior Southcentral will be highly
dependent on the amount of cloud cover slipping over the ridge
from the north as the ridge moves south. Overall, forecast
confidence continues to be low with temperatures. While there`s
moderate confidence in the general trend, the exact numbers have
been difficult for models to home in on as temperatures have
largely been dictated by diurnal (radiational warming and cooling)
rather than dynamic (advection of cooler or warmer air masses)
effects, which models struggle with. As such, keep an eye more
towards temperature trends than exact numbers.

The position of the development of a weak surface low in the
northwest Gulf will also dictate the extent of wind flow up
Cook Inlet and additional fog / low stratus development into
Sunday. Confidence is low with when or where dense fog might
form, but the introduction of moist air into an otherwise dry and
thermally stable air mass provides a good weather pattern for fog.
As it is currently foggy in Anchorage, confidence is higher that
fog will redevelop over Anchorage for Sunday morning.

Moving ahead to Sunday evening, the entrance of a low into Central
and Interior Alaska will bring an end to our recent spell of dry
weather. Cold temperatures over Southcentral should keep
precipitation as all snow, with maybe some mixing along the Prince
William Sound coast and around Homer. Snow amounts will generally
be around and 1" for the Western Kenai Peninsula, 2-4" for the
Anchorage Bowl, and 3-6" for the Mat-Su Valleys. Currently, the
highest amounts look to be around Willow and north and east of
Palmer. Models, however, tend to have difficulty with how quickly
blocking ridges are broken down and shunted downstream, so stay
tuned as the snow forecast could change. The current forecast does
reflect a slightly later time for the onset of snow late Sunday
night / early Monday morning.

-TM/Chen

&&


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

The main weather features for Southwest Alaska and the Bering Sea
are a strong high pressure ridge over the southern Mainland and a
low pressure system and trough over the western Bering. Through
the coming days the ridge will push off to the east as the low
pressure system moves east into the Interior through Monday.
Currently the leading front from this system is over the Pribilof
Islands and it will push east into the Kuskokwim Delta later
today and overnight. With the high pressure in place there is a
significant temperature inversion, which may allow for light
freezing rain later today and overnight for the Kuskokwim Delta,
particularly over areas away from the coast and more sheltered
from the wind. This will be fairly short-lived and temperatures
for the most part will be above freezing and precipitation will
fall as rain.

Moving into Sunday the front will slowly push inland, bringing a
mixture of rain and snow to Bristol Bay and the Lower Kuskokwim
Valley. Cold air will slowly wrap in behind the front, which will
allow areas receiving rain to transition back over to snow by the
end of the event. Precipitation will end for the most part by
Monday morning, though some light upslope flow will lead to
lingering snow on western facing terrain. By late Monday and into
Tuesday expect temperatures to fall somewhat rapidly as cold and
dry air filter back into the region from the northeast and an
arctic trough drops south.

&&

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

Big changes on the upper level Alaskan Weather map through this
forecast period. A moderately strong shortwave stalls over
Interior Alaska through the week. This effectively anchors colder
air further South over the Mainland through Friday. The upper
level ridge across the Southern Gulf of Alaska retreats into the
Eastern North Pacific, and in its wake, a developing low center
migrates from the North Pacific. This low moves to the Southern
Alaska Peninsula and links up with the Mainland trough for the end
of the week. An ECMWF / GFS / UKMET ensemble holds the individual
strengths and tracks pretty well. Canadian model was a bit of an
outlier. In the West, an Eastern Siberian ridge build over the
Bering, completing the reversal of the previous weather pattern.

A surface front ahead of the shortwave trough presses across
Interior Alaska through Wednesday with areas of snow almost all
the way to the Southcentral coast. Coastal zones East of Prince
William Sound may see a mix of rain and snow for Wednesday. The
approaching North Pacific low brings gale force winds to the
Bering, and moderate rain to the Western and Central Aleutians
Tuesday. The winds diminish over the Bering for Thursday, but
develops further Eastward, spreading snow mixed with or changing
to rain over the Eastern Aleutians and Alaska Peninsula to Kodiak
Island for late Wednesday. On Thursday and Friday, the area of
mixed precipitation will spread along the Southcentral coast.

&&

.AVIATION...

PANC... A ridge over the area has created a prolonged period of
light winds. VFR to MVFR conditions are expected later this
morning as fog moves southward. The greatest chance for fog at
the terminal is from 14Z through 18Z today. Southwesterly flow
will dominate this evening and tomorrow resulting in another
chance for fog from 06Z through 12Z tomorrow.



&&


$$