Gale Warning 60, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
447 PM AKST Sun Jan 9 2022

.ANALYSIS AND UPPER LEVELS...

The large surface ridge centered north of the Arctic coast has a
ridge axis stretching across far eastern Russia and through the
western Bering Sea. The strength of this ridge is reflected in
the low south of the Aleutians, which has been unable to make
much headway northward for the past few days due to the ridge.
Where a low is making progress is in the Gulf of Alaska where a
strong low is pushing warmer air and moisture into the area across
the Gulf and toward Southcentral Alaska.

While Southcentral is warming up, the Bering Sea region is
cooling as the cold upper level low that was centered over the
Copper River Basin just two days ago has moved west. An upper
level disturbance that is moving in conjunction with the upper low
brought some snow to the Southwest mainland earlier today, but
has a sharp back edge where it is clearing out and leaving more
clear skies between this wave and the clouds from the Gulf low.

This pattern is putting the Bering Sea in a tight pressure
gradient with north-to-northeast flow. The colder air at the
surface is evident in visible satellite imagery in the Bering
Sea, with widespread cloud streets of stratocumulus. Two days ago
it was noted how there was a lack of low clouds streaming off the
ice edge when the temperatures in the Pribilofs were right around
the freezing mark. Today the temperatures there have dropped into
the lower teens. That cold air over the open water of the Bering
Sea is now creating low level instability resulting in cloud
streamers and snow which are filling most of the Bering Sea.

&&

.MODEL DISCUSSION...

Models remain in good synoptic agreement through most of the week.
In the short term the model differences will remain on more of
the details such as QPF amounts and local winds. In the mid-week
timeframe, the elongation of the low over the Aleutians and Alaska
Peninsula is handled a bit different by the models. The good news
is that the main trough axis at the surface is mostly agreed upon.
It is the manner in which multiple weaker lows develop in this
region along that trough axis which may impact the forecast. As we
get late in the week, the model agreement improves again as they
all lock onto a strong low in the North Pacific that should start
to weaken as it moves northward into the area.

&&

.AVIATION...
PANC...Moisture associated with a storm system tracking across
the Gulf will lead to lowering ceilings. However, persistent
northerly winds at the surface will maintain lots of low level dry
air. Thus, ceilings will remain safely in the VFR category.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Wed)...

A moderately deep North Pacific low arrived in the Gulf this
morning with its leading front impacting the Gulf Coast this
afternoon. The low center remains in the southern Gulf and will
slowly move north while consolidating and weakening near the
Barren Islands Monday morning. Outflow winds will weaken overnight
as the interior airmass warms and the thermal and pressure
gradient weakens. Most of the precipitation on Monday will remain
confined to the Chugach Mountains, where high winds, warming
temperatures, and moderate QPF will produce heavy snow overnight
tonight and into Monday morning. Some light spillover is possible
from the Western Kenai north to the Mat Valley at times but only
trace to very low accumulations are expected should this occur.
Warm air accompanying the system will cause mixed precipitation
below 1200 ft for the Eastern Turnagain Arm and Valdez areas.
Valdez precipitation type remains somewhat uncertain with the
possibility that the low level warm air remains unable to make it
over the mountains to the south of Port Valdez. If the warm air
does make it over the mountains, snow and freezing rain is likely.

A secondary shortwave is expected to move north through the
western Gulf and into Southcentral Tuesday morning. The change in
the wind field aloft to be less conducive to downsloping as well
as the reintroduction of upper level forcing will allow for a
quick shot of 0.5 to 1.0 inch of snow from the Cook Inlet region,
and Mat-Su Valleys. There are some timing inconsistencies between
models but the majority agree on some light snow just prior to
the morning commute Tuesday morning. On Wednesday yet another
shortwave will make its way over Kodiak Island and into
Southcentral, providing another chance for snow. Overall the
mid to upper level wind field will be more out of the south to
southwest, which will favor snow chances for the Cook Inlet north
to the Susitna Valley. Uncertainty with these feature is moderate,
but overall temperatures are more conducive to snow over most
areas as compared to the one currently impacting the region.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3/Tonight
through Wednesday)...

A series of upper level troughs will bring periods of light snow
to the area. Tonight will be clear and cold with strong winds
continuing for the Kuskokwim Delta. For Monday an upper level
shortwave trough will move across the area. This will allow light
snow to develop across Bristol Bay tomorrow morning and continuing
through Monday night with an inch or less snowfall expected. Snow
will move across the Kuskokwim Delta by early Tuesday morning
with only light accumulations expected. This shortwave will also
begin to usher in slightly warmer temperatures by Tuesday. Another
shortwave trough will move across the area by Tuesday afternoon
through early Wednesday morning with more snow expected, but once
again only an inch or so of accumulations expected. On Wednesday a
stronger shortwave will push a front across the area with warming
temperatures and a good chance of snow. This system may bring a
bit more snowfall, but uncertainty remains on amounts as models
differ on the strength of this system.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3/Tonight
through Wednesday)...

High Pressure over eastern Russian and low pressure near the
Aleutians will continue to drive northeast gale force winds
across a good portion of the Bering Sea through Monday and will
begin to decrease as the pressure gradient weakens on Monday. An
upper level low will push a cold front across the central and
western Bering through tomorrow with increasing chances of snow
showers this front will move across the central and western
Aleutians tonight and Monday with a good chance of snow showers.
By Tuesday this front will move into the North Pacific. Otherwise
a persistent area of low pressure south of the eastern Aleutians
will meander northward and eventually push into the southern
Bering Tuesday night and Wednesday and will also push a front into
the eastern Bering bringing warmer air and rain. This system will
also bring an area of Gales mainly near the front and surface low.

&&

.MARINE (Days 3 through 5 - Wednesday through Friday)...

Gulf of Alaska: A strong rapidly-moving front connected to a North
Pacific low will usher a widespread area of gales including
strong gusts and large seas of more than 22 ft across the Gulf,
starting Wed night through Fri afternoon. As the weakening front
transitions into an open trough, winds along the Prince William
Sound could still reach gale-force strength as another round of
lows trails behind the trough, reinforcing the winds and seas to
remain near hazardous levels into Fri night. These systems from
the Pacific will mainly bring warm temperatures and freezing spray
should not be much of a threat.

Bering Sea: A trough of low pressure lingering over central
Aleutians/Bering Sea combined with a cold Arctic airmass could
potentially elevate seas and winds to gales offshore between Wed
and Thu. Elsewhere, wind and sea conditions are expected to
remain benign through the forecast period.

&&

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

Multiple short-wave troughs from the Gulf will enter Southcentral
into Sat morning, bringing rain/snow mixed mainly over the coastal
areas and light snow farther inland. A trough of low pressure
lingering over Prince William Sound will enhance clouds and
potential for rain there for the weekend, where winds will also
remain elevated with much stronger gap winds as well. Over the
Bering, the onset of a North Pacific low and its associated front
could drive gales and increased precipitation across the
Aleutians/Bering starting Sat morning before reaching Southwest
Coast Sun night. Prior to this event, a train of isolated short-
waves from south of Alaska Peninsula and Bering Sea transits
across Southwest starting Thu morning. These features could bring
increased clouds and rain/snow mixed for the Southwest coast and
light snow farther inland. Although strong ridging aloft will
remain over the Mainland, warm temperatures ushered by North
Pacific systems will at least maintain warm temperatures for
coastal areas through much of the long term.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 131 Thompson Pass.
MARINE...Storm Warning 127 128.
 Gale warning 119 120 121 130 131 138 139 170 173 174 175 176 185.
 Heavy Freezing Spray Warning 165 179 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...CJ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RC
MARINE/LONG TERM...CB