Gale Warning 38, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
507 PM AKST Fri Jan 6 2023

.ANALYSIS AND UPPER LEVELS...

A longwave trough continues to extend from the Bering to
Southcentral Alaska. A nearly zonal jet remains south of the
region and along the 35th parallel. Across the Aleutian Chain this
morning, numerous weak lows are circling around a stationary and
weakening upper level low. Rain and wind are noted from Atka to
Dutch, while a mix of rain and snow is being seen through Shemya.
The Anchorage Bowl had a taste of fog early in the morning as
this morning's upper air sounding showed minimal winds from the
surface to the upper levels. Mid afternoon satellite analysis
shows a bank of low stratus and fog stretching from the Knik
river, southwest through the northern half of Cook Inlet.

&&

.MODEL DISCUSSION...
If only it were good to be bad... it feels like groundhog day
again as models really struggle once the time period is out of the
immediate short term. The forecast period of now through about 24
to 36 hours is reasonable synoptically. After that point, models
tell semi similar stories, but some of the differences are
depicting lows nearly 600 miles apart from each other. Looking
past the weekend and into the extended forecast there is better
agreement amongst all guidance with a deep north pacific low as
well as a second deep low south of Shemya.

&&

.AVIATION...
PANC...Ceilings and visibilities are expected to bounce between
VFR and LIFR throughout the evening and overnight with fog moving
in and out of Anchorage. Complications arise towards morning.
Guidance indicates that some clearing is expected through the
evening, but will turn to low stratus and fog into the morning
hours on Saturday. With no winds at the surface or aloft, concern
that this fog/stratus remaining through Sunday will linger.

&&

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

It is a challenging forecast for the next few days, first with fog
and then with details of storm systems tracking out of the Pacific
and into the Gulf of Alaska. Fog is lingering over Cook Inlet this
afternoon. As the sun sets and radiational cooling kicks in,
expect a surface-based inversion to quickly form and fog to
expand. The one wild-card is a mid level cloud deck sitting over
the western Susitna Valley. It will rotate across far northern
Cook Inlet and then northward across the Susitna. This could
initially keep fog from forming in these areas. Otherwise, the
environment looks ideal for fog with clear skies and light winds
through a deep layer. Therefore, expect areas of fog, possibly
dense, to settle over Cook Inlet, the western Kenai Peninsula,
Anchorage, the Matanuska Valley and the southern Susitna Valley
tonight. While there may be some erosion of fog on Saturday under
full sun, it looks like areas of fog will persist until clouds and
a chance of snow arrive on Sunday.

There have been some changes in track and timing of key features
moving out of the Pacific which will delay the return of precipitation
to coastal Southcentral. A leading warm front now looks weaker
and farther south on Saturday, perhaps bringing some light snow to
the Cordova area Saturday afternoon. More impressive is an upper
level short-wave which will lift northward across Southcentral
Saturday night through Sunday. Eastern Prince William Sound into
the southern Copper River Basin will see the best lift (and
highest precipitation totals) ahead of the short-wave before it
begins to weaken. As you head north and west from Prince William
Sound it looks like a quick shot of precipitation sometime
Saturday night or Sunday. Expect snow most areas, with snow
changing to rain along the Gulf coast on Sunday.

It now looks like a much larger and deeper low will form south of
the Gulf on Sunday and persist through Monday. This will favor
strong winds and rain for Kodiak Island. and the Gulf waters. The
big uncertainty is how far north the frontal system and associated
precipitation will extend. Wit the southward trend in low location
it is looking less favorable for heavy precipitation in the Prince
William Sound area. Easterly upslope flow may favor continuous
light precipitation for the eastern Kenai Peninsula, with heavier
frontal precipitation just south of the Kenai Peninsula. The rest
of Southcentral looks quiet late this weekend into early next
week. Stay tuned to the latest forecasts as we continue to
monitor the track of these storms in the Pacific and Gulf.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Sunday night)...

Fairly quiet conditions will ensue across Southwest through Sunday
before the next system moves in from the east. A weak shortwave
that is decaying rapidly is currently over the Alaska Peninsula,
bringing light snow showers to Port Heiden and Pilot Point. These
will linger through the morning before the upper level support
drifts off to the northeast. On Saturday, a shortwave ridge will
build over the area, leading to clearing skies, increasing offshore
flow and cooling temperatures. Fog will likely be patchy across
the region Saturday before winds ramp up and mix out any moisture
near the surface by Sunday. On Sunday, a stronger system will try
to poke into this ridge from the east, bringing a return of light
snow. There is still a lot of uncertainty in the timing of this
system, as models continue to struggle resolving it's evolution in
the Gulf of Alaska. Confidence is increasing over Bristol Bay,
where snow looks likely to begin Monday morning, but whether or
not any will make it north onto the Kuskokwim River areas remains
uncertain.

&&

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

A conglomerate of lows will continue to spin around each other
over the central and western Bering. One of these systems is
currently north of Adak, with another over the north Pacific
expected to cross over Adak Saturday morning. The last of these
stronger systems is moving over the Chain Sunday afternoon.
Precipitation type will be a mixture of rain and snow. By late
Sunday and into Monday, a much stronger low will develop well
south of the Bering, which will keep energy and baroclinicity away
from the aforementioned complex of lows, resulting in a quieter
pattern developing over the area.

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

Key features in the long term include an upper level trough over
the western half of the state Tuesday morning. This will quickly
lift northward, generating snow showers across the Kuskokwim Delta
Coast. On the eastern side of this feature, several upper level
waves over the Gulf will lift northward over Southcentral,
introducing the possibility for precipitation, especially for
areas along the coast. Meanwhile the more significant feature of
note is a broad upper level low that moves from the North Pacific
into the Bering on Wednesday. Models have been far more
consistent with this feature, and are advertising a fairly deep
and broad low to impact the Bering and Aleutians Wednesday into
Thursday. If this pans out, would expect widespread precipitation
and gusty winds, especially along the Chain. Farther east during
this time, a broad upper level ridge over the Alaska- Yukon border
seeks to build across the mainland along an axis oriented from
southeast to northwest. This would introduce generally fair and
calm conditions for Southcentral. Currently, this pattern is looking
fairly progressive. By Friday, the Bering low will lift
northward, allowing several additional upper level shortwaves to
traverse south to north across the Bering and over the Southwest
Alaska coast by next weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 173-176 179 185 352 411-413.
		 Heavy Freezing Spray Warning 180 185.
FIRE WEATHER...NONE.

&&

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