Gale Warning 729, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
520 AM AKST Tue Nov 15 2022

.ANALYSIS AND UPPER LEVELS...

Quiet and cool weather has taken hold of the Southern Mainland as
ridging builds in from the east and west. Under clear skies
termpatures have been able to fall across most areas, but fog and
low stratus have also developed in the Susitna Valley and through
areas of the Cook Inlet. Out west, some areas of fog and stratus
exist over Interior Bristol Bay and the Lower Kuskokwim Delta, but
these areas are rapidly diminishing as winds increase. Over the
Central to Western Bering a storm force front is pushing warmer
temperatures and rain north towards the Chukchi Sea. A large
occluded low in the North Pacific has send it's front north into
the Western Gulf, bringing elevated winds and eventually rain to
Kodiak.

&&

.MODEL DISCUSSION...

Models are in good agreement in the short term with large synoptic
features to lock into. The most impactful area of uncertainty is
over Southwest Alaska late Wednesday and into Thursday in regards
to the placement of upper level features moving northeast across
the area. While the overall forcing is weak, the timing and
placement of precipitation will impact the forecast for potential
of light freezing rain. Otherwise, fog/stratus and their impacts
on temperatures will be the other challenge.

&&

.AVIATION...

PANC...Mostly VFR conditions and light northerly winds will
persist through the TAF package. Fog has moved over the Terminal
from the north and is expected to dissipate and move towards the
mountains around sunrise.

&&

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

An upper level ridge building from the Bering Sea to mainland
Alaska will merge with a ridge building from the northwest CONUS
to the Gulf of Alaska. This will lead to an anomalously strong
ridge centered along the ALCAN on Wednesday. This ridge will
gradually shift eastward through Thursday, though remain firmly
over Southcentral. As a result, expect dry weather and abundant
sunshine to prevail for the next few days. The only fly in the
ointment will be localized areas of fog as low level temperature
inversions steepen due to surface cooling and warming temperatures
aloft up the west side of the upper level ridge. Areas of fog this
morning from the southern Mat-Su to Anchorage and the western
Kenai Peninsula will dissipate as northerly winds strengthen and
the sun warms the surface later this morning. Generally expect
some wind and vertical mixing to remain around through Thursday,
limiting the ability of fog to re-form. If it does form, expect
it to be localized. The one exception is the Copper River Basin
where winds will remain light. Expect areas of fog to form tonight
and possibly hang around through the remainder of the week as
strong inversions remain in place.

Meanwhile, a large vertically stacked low will remain nearly
stationary over the North Pacific to the south of Kodiak island
and the Alaska Peninsula. A series of upper level short-waves
and surface fronts will track westward across the Gulf to Kodiak
Island, bringing wind and rain, especially to the east coast of
Kodiak. There could be some very light rain as far north as the
south to eastern Kenai Peninsula tonight/Wednesday as warm air
overrides cooler air in place, but it won't be much and will be
short-lived.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Tuesday
through Thursday night)...

A strong blocking ridge over Southwest Alaska continues to promote
colder temperatures inland and weaken or ward off precipitation
for the area. Lingering patchy fog from last night will dissipate
as the morning progresses and with clear skies expected for
Southwest Alaska today. Weak offshore flow will mitigate the fog
chances for areas in the Greater Bristol Bay area tonight. More
inland, low-lying areas such as Aniak, may expect to see some
patchy fog again tonight.

An approaching shortwave from the North Pacific will bring
precipitation to the Alaska Peninsula by tonight. Rain will be the
predominant precipitation type along the Alaska Peninsula as the
the wave crosses into our territory. By early Wednesday, this wave
has the potential to bring very weak precipitation to Southwest
Alaska, this along with warmer temperatures aloft and lingering cool
surface temperatures, has the potential for freezing rain in
areas such as Dillingham and Bethel Wednesday and Wednesday night as
the wave pushes up. There is good agreement in the models that the
precipitation will be limited due to the presence of the ridge,
however further details remain obscure due to uncertainty. Of the
precipitation that does make it to Southwest, it will be mostly limited
to southeasterly faces of the Alaska/Aleutian Range and Kuskokwim
Mountains, with lower elevations staying mostly dry due to
downsloping. In summation, freezing rain is possible for Wednesday
and Wednesday night, however precipitation (if any) will be light,
with minimal associated ice accumulations. Chances for
precipitation will linger into Thursday, however warming
temperatures will shift precipitation across much of Southwest to
rain.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Tonight through Thursday)...

A low moving off of the Kamchatka Peninsula to the north will
continue to drive a strong front across the Western Aleutians into
the Central Aleutians by this evening. Storm force southerly winds
within the core of the front will weaken to gales tonight.
Freezing spray is not of concern with this frontal boundary as the
temperatures are too warm, mostly attributed to the intense
southerly flow. As the front approaches Adak, its mother low will
push back into mainland Russia, weakening its influence on the
front which will stall in the Central Bering and decay by
Wednesday morning. Light to moderate precipitation expected to
persist along the frontal boundary until Wednesday afternoon. The
Eastern Aleutians and Pribilof Islands will not see an effect from
this front.

The Eastern Aleutians have an approaching low south of the Chain
that will move over the Eastern Aleutians by tonight. This low
will bring precipitation in the form of rain to much of the
Alaska Peninsula and Eastern Aleutians before pushing into the
Eastern Bering Wednesday afternoon. The Pribilofs have a chance to
receive some rain from this system as it moves through, merging
with the remnant aforementioned frontal system, and pushing north
out of the region. A reinforcement of moisture will bring another
stronger wave of precipitation to places near Sand Point and Cold
Bay by Thursday.

&&

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

A persistent ridge of high pressure will stretch across much of
the Mainland through the long term. This will promote generally
benign conditions across Southcentral through Sunday. Deep
southerly flow with the ridge will result in above average
daytime high and overnight lows are advertised for both
Southcentral and Southwest Alaska through the weekend. Upper-level
shortwaves within the upstream ridge flow will track across
Southwest Alaska and maintain periods of precipitation through
Saturday morning. Meanwhile, an upper-level low and its associated
surface low are expected to move into the Gulf of Alaska. At this
time, precipitation and winds accompanying the aforementioned low
and front look to stay confined to the Gulf waters through
Monday.

Out west, an upper-level trough located over the Bering on is
expected to lift northeast towards the Bering Strait by Friday
morning. Precipitation will subsequently clear across the Bering
with the exit of the trough and the development of a shortwave
ridge. Any respite from precipitation across the Bering will
likely be short lived as a front extending from a North Pacific
low is expected to reach the western Aleutians Friday morning and
track into the Bering through the weekend. Model spread grows in
association with the exact track and strength of the low and its
front, but a consensus of widespread rain and gale force winds are
currently advertised to accompany the low. Current GFS model runs
are advertising the aforementioned low tracking northward across
the Alaska Peninsula and into the eastern Bering with widespread
gale force winds located in the western and central Bering.
Meanwhile, recent Canadian and EC runs are showing the track more
eastward towards the Gulf with a swath of small craft winds
roughly located over the eastern Bering.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 177 178 185 411
Gale Warning 130 132 352 150 155 175 176 180 412 413.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CJ
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CL
LONG TERM...NS