Gale Warning 835, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
436 PM AKST Mon Dec 19 2022

.ANALYSIS AND UPPER LEVELS...

The omega block pattern remains in place over the northern and
eastern Bering Sea into the Arctic. Over Southern mainland
Alaska, this pattern is bringing in northerly flow aloft and
mostly clear skies. There is once again some fog and stratus over
northern Cook Inlet and the northern Kenai Peninsula. The cold air
outflow out of the eastern Kenai Peninsula has helped to spin up
a surface low in the northern Gulf of Alaska. This low is pushing
clouds into the Prince William SOund area snow showers are
probably in the areas near Cordova, but with the Middleton Island
radar still not working, it is hard to tell the extent of the snow
showers. This low is also pushing some mid-level clouds over the
Kenai and Chugach Mountains.

&&

.MODEL DISCUSSION...

Model agreement remains good on the synoptic scale upper level
pattern the next few days, but even by the weekend there is a
significant breakdown over the Bering Sea region. There will be a
series of surface lows that develop in the north Pacific and ride
the nearly stationary front that will stretch from the Alaska
Peninsula to the northern Kamchatka Peninsula during the mid-
to-l;ate week period. By late Wednesday, the forecast confidence
rally starts to diminish especially for the Pribilof Islands due
to the uncertainty on the low tracks and strength.

In the northern Gulf of Alaska, models are in a little bit better
agreement today with the anticipated behavior of the surface low
that is currently in the vicinity of Middleton Island. While
differences remain, they are also all now detecting the weak 500
mb low in the interior which will sink southward over the surface
low and infuse it with a little more strength in the coming days.

&&

.AVIATION...

PANC...Periods of fog will continue to haunt the airport through
tomorrow morning. When the fog is not around, VFR conditions and
light winds will occur.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Tonight through Thursday)...

High pressure is retreating northward and into the northern
Bering this evening. Dry and cooler northerly flow at the surface
has crept into all of Southcentral with predominantly clear skies
for all but far eastern portions of the Copper River Basin. The
development of fog during the overnight hours Sunday night was a
nuisance for the morning commute across the Anchorage Bowl and
even a bit of light snow was spotted on the west side of town due
to precipitating low stratus clouds. For tonight and into Tuesday
morning fog redevelopment will again be possible. On satellite, a
surface low over the northern Gulf and just south of Prince
William Sound is meandering further west, which should bring
increasing cloud cover across the Gulf coast along with increasing
snow chances as southerly flow pushes Gulf moisture into the
coast. Snow amounts will be negligible from Cordova up into
Valdez. A better chance for snowfall accumulations will exist over
the eastern Kenai Peninsula mountains. Latest models have trended
snow amounts down for the lower elevations, but Whittier could
see a few or more inches Wednesday into Wednesday night.
Otherwise, precipitation chances will remain low for inland
portions of Southcentral. A front is forecast to move into Kodiak
Island Wednesday into Thursday, which will see a potential mix of
rain and snow through Thursday. Otherwise, Southcentral will
remain cold and a new shot of cold air may begin to spread into
Southcentral by the end of the week.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: This afternoon
through Thursday afternoon)...

Quiet, clear, and cold weather continues to be the status-quo for
much of Southwest Alaska as the ridge of high pressure on the
western coast has been slow to relent. However, the ridge does
appear to weaken and move slightly westward during the day on
Tuesday and this paves the way for an upper trough to move
westward from the interior of the state towards interior portions
of Southwest. This will pave the way for cold air advection from
the northeast and will provide for a very cold day for Tuesday as
highs will only reach the single digits for most of Bristol Bay
and the Kuskokwim Delta. Interior areas of Bristol Bay and the
interior portions of the Kuskokwim Valley will only reach the mid
negative teens to low negative single digits for day-time highs.
The only exception to the norm is the southern Alaska Peninsula
where warmer southerly to southeasterly flow resides and continued
chances of upslope rain showers. A "warming" trend comes on
Wednesday when flow switches to southeasterly aloft and a frontal
system approaches the coast from the Bering Sea potentially late
Wednesday night into the day on Thursday. However, details still
need to be ironed out as far as timing and precipitation threats
are concerned with the system.

&&

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

The active weather pattern out in the Bering Sea, for the
Aleutian Chain, and the Pribilof Islands will continue through the
short-term. An upper level low near Kamchatka continues to be the
dominant player in the weather scheme for the area. Multiple
shortwaves from this low continued to be ejected eastward towards
the Bering and Aleutian Chain. The pressure gradient between the
frontal zone in the Bering and higher pressure in mainland Alaska,
have created a belt of southeasterly gales through the central
Bering roughly from outside of Dutch Harbor, through the
Pribilofs, to west of Saint Matthew Island. Areas of storm-force
winds are possible Tuesday afternoon through Wednesday night in
the central to northwestern Bering and extend down into the
Pribilofs very early Wednesday morning through mid morning. There
is still some uncertainty in exactly where surface lows will spin
up and deepen and the eventual tracks they may take, due to so
many moving parts (shortwaves) in the atmosphere, especially
during Wednesday evening and on Thursday. While the dominant
precipitation type is rain, there is the chance that the central
to western Aleutians and Pribilofs to see some rain/snow mix at
times as colder air works in to the various systems. Pay attention
to the latest forecast updates as features hopefully become better
resolved with time.

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

Model consensus beyond day 3 breaks down. The general synoptic
patterns resolve reasonably, but the position and phasing of the
systems differ and will likely impact the forecast outcome. Strong
easterly winds Thursday, spanning from the Gulf through the
Alaska Peninsula to the Bering should begin to diminish for Friday
when a surface low and an accompanying front sets up in the Gulf.
This front should bring plenty of moisture. Many areas could be
cold enough for snow down to the coast and Kodiak Island.
Increased surface pressure gradient with the incoming low, could
enhance gap winds through the Matanuska Valley and other northeast
and north to south terrain gaps. An upper trough over northern
Canada and Alaska will drop south through mainland Alaska and
elongates as it reaches Southcentral. This appears to form a
closed off circulation that moves west into the southern Bering
Sea Saturday and potentially phase with a low just south of the
Aleutian chain. A broad area of low pressure near the Aleutians is
expected to continue, with clusters of pressure minimal that would
continue to bring nuisance activity from weak low systems that
phase and interact with one another. The initial entrance of a low
in the Gulf towards the end of the week however, could be the
time the blocked ridge breaks down enough for active weather to
return to northern Gulf. Come Sunday night through Monday night,
another train of back to back lows from the Pacific could move
into the Gulf.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 179 185.
		 Gale Warning 119 130 139 155 160 165 170-172 180 181.
		 Heavy Freezing Spray Warning 139 160 180 181 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DN
LONG TERM...VR