Dense Fog Advisory 2, NWS Anchorage, AK

347 
WWAK71 PAFC 252106
NPWAER

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
1206 PM AKST Mon Jan 25 2021

AKZ101-252215-
/O.EXP.PAFC.FG.Y.0002.000000T0000Z-210125T2100Z/
Anchorage-
Including the cities of Anchorage, Eagle River, Indian, 
and Eklutna
1206 PM AKST Mon Jan 25 2021

...DENSE FOG ADVISORY HAS EXPIRED...

Pockets of dense fog with 1/4 mile visibility will continue 
through the afternoon. The worst conditions have been reported 
near Palmer and Eagle River. However, fog is not expected to be
widespread and should continue to lift by late afternoon.
Motorists should continue to use caution.

$$

For more information from the National Weather Service visit
http://weather.gov/afc

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
419 PM AKST Sun Jan 24 2021

.ANALYSIS AND UPPER LEVELS...

The upper level disturbance that caused the widespread snowfall
for much of the Cook Inlet region last night into this morning is
winding down this afternoon as drier air and clearing skies press
southward out of the interior. Outflow winds are already
increasing through Resurrection Bay and Thompson Pass, and the
outflow wind theme will become dominant in the coming days. More
on that below. Fog and low stratus have been impacting parts of
Southwest Alaska, including through the Kuskokwim Delta, and
coastal Bristol Bay. A front moving east across the eastern Bering
and Aleutians is spreading some cold rain which is approaching
Dutch Harbor, with rain or a rain/snow mix moving into the
Pribilofs. The front is associated with a large low in the western
Bering, centered north of the Western Aleutians. The low is
already fully occluded and is in the process of weakening and
dissipating. Nevertheless, gales extend over large swaths of the
western Bering this afternoon.

In the upper levels, shortwave ridging extends over Southwest
Alaska, with a longwave trough and associated upper level low over
the western Bering, with a 160 kt jet streak over the North
Pacific south of the Aleutians. Very little is over Southcentral
with the upper level disturbance dissipating, leaving nearly calm
wind flow over the area.

&&

.MODEL DISCUSSION...

Model agreement is excellent this afternoon, as the pattern
becomes much less complex with time. Cold high pressure builds
into mainland southern Alaska through Tuesday, leading to clearing
skies, colder temperatures and strengthening outflow winds through
the gaps. Otherwise, the weather becomes very quiet over the
mainland for the next couple days. Meanwhile all of the stormy
action will be out over the Bering, as a strong North Pacific low
moves into the western Bering from Monday night on. The models are
also in excellent agreement with this feature as well. The main
challenges will be precipitation type with temperatures hovering
near freezing, and how strong the winds ultimately get to. More
details on that storm below. Thus, forecast confidence is very
high today.

&&

.AVIATION...
PANC...VFR conditions and light southerly winds will persist into
this evening. As skies clear aloft, the threat for fog development
will increase through the night. As usual, there is significant
uncertainty as to when the fog will develop and how dense it will
be, but is expected to cause periodic IFR to LIFR conditions into
Monday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Wednesday)...
As the remnants of the rapidly weakening upper level low that
brought snowfall to much of Southcentral this morning move into
the Gulf, clearing skies and falling temperatures are quickly
moving into the region from the north. This trend will bring clear
skies to most areas, and along with diminishing coastal winds,
the possibility of fog. This fog is most likely in the Cook Inlet
area tonight. There is also an outside chance that this fog could
develop in the Copper River Basin as well, especially in the
vicinity of the Copper River.

Starting tomorrow, the region will get a well deserved break from
the active weather that has occurred for most of January. With
the exception of a weak Gale force low that will clip the southern
edge of Kodiak Island for Monday, will a return to clear skies
and below normal temperatures that will persist into Wednesday.
The one impact from this pattern will be for the potential for
gusty outflow winds along the North Gulf Coast, especially near
Valdez and out of the Copper River Delta.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

Quiet conditions are set up across Southwest Alaska today as there
is a break in the weather before the next system moves in. Most of
the low stratus and fog that developed across the region overnight
has burned off by this afternoon, allowing for clearing skies for
the mainland. The cloud cover returns as a weak front approaches
the Southwest coast this evening bringing a few showers into
early Monday, but this activity shouldn't move to interior
locations. Dry conditions return on Monday through Tuesday
afternoon before the weather quickly shifts to a much cloudier
and wetter pattern

Late Tuesday, there is high confidence in a front moving over the
Southwest coast. However, models are still having a difficult
time with the timing of this system moving into the forecast area
and how far inland the front will move through Wednesday. In any
case, this organized system is likely to bring widespread snow and
accumulations of a few inches across Southwest Alaska.

&&

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

The active weather pattern across the Bering continues today with
a low in the western Bering. This system will bring widespread
precipitation and an area of storm force winds this evening,
which will then lift northward and weaken through Monday evening.
To the east, a developing North Pacific low will move towards the
eastern Aleutians by this evening, which will also bring a swath
of storm force winds to southern parts of the eastern Aleutians.
Warmer temperatures with this system will allow for a mix of rain
and snow, which will transition to all snow overnight. Strong
winds with this low could lead to blowing snow at times, but
should not significantly reduce visibility in this setup.

Over the western Aleutians Tuesday morning, a storm force front
moves over the Chain, which will see embedded hurricane force
winds. Precipitation will initially start as snow, transitioning
to rain or a mix of rain and snow throughout the day as the low
center lifts over Shemya by Tuesday afternoon. To the east of
Shemya, cold air moving into the backside of the low will allow
for a brief period of elevated seas and sustained hurricane force
winds, which will weaken to storm force Tuesday night into
Wednesday as the low track farther north. The main concern over
land areas for this system will be the potential for blowing snow
for the western Aleutians. However, temperatures with this system
will be the determining factor for precipitation type and blowing
snow potential. Expect widespread gale force winds and
precipitation to continues across the Bering and Aleutians
throughout the day on Wednesday.

&&

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

Gulf of Alaska: Good model agreement with good forecast
confidence early on and then lower confidence by Friday. Late
Wednesday into Thursday a front with a gale force winds and a low
forming just east of Kodiak Island will track towards Prince
William Sound however some differences on evolution of this low
regarding strength and track. On Friday this low will slowly turn
south and weaken with mainly small crafts during this period,
although still some uncertainty on track of this low, so lower
confidence for Friday.

Aleutians/Bering: Good model agreement with good forecast
confidence. A front exits the eastern Bering on Wednesday with
Gales but decreasing late Wednesday as the front moves east. A
strong low moves over the Bering Wed through Thu. Widespread storm
force winds and waves with areas of hurricane force winds with
the wind wrapped low. This system diminishes to widespread high
end gale force winds with local areas of storm force winds
spreading over the Bering and to the Alaska Peninsula for Thu.
Wave heights to 45 feet on the Pacific side and 39 feet bering
side spreading north and east subsiding Thu. Friday mainly Gales
across a good portion of the area as this low weakens and moves
east, while another low approaches the Western Aleutians Friday
bringing more Gales.

&&

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

Models are in fairly good agreement through the long term with the
key features, this leads to higher than normal confidence for this
forecast period.

A fairly zonal pattern will remain in place Thursday and Friday
across the Bering and Aleutians with an amplified ridge breaking
up this pattern across the eastern Gulf. On Thursday a strong
shortwave will be moving across the eastern Bering. As it moves
into the Gulf, it strengthens with a triple point low forming
along a frontal boundary just east of Kodiak Island. This system
will bring a good swath of precipitation to much of Southwest and
Southcentral Alaska. As this low moves through Gulf the ridge will
move into western Canada. On Friday and Saturday a low up in the
Arctic regions will dip south through the mainland of Alaska
bringing colder temperatures to Southwest and Southcentral Alaska
by next weekend.

Out west a strong ridge will develop Friday and Saturday in
response to two strong lows moving across the northwest Pacific
pumping warm air into the ridge and building it. On Sunday this
ridge will slowly move east across the Bering with a low pressure
system approaching the western Aleutians sometime on Sunday. This
ridge will allow northwest upper level flow across much of the
mainland of Alaska and into the Gulf allowing colder arctic air
to move into the area next weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 132 150 165-175 185.
		 Storm 155 176 177 178
		 Heavy Freezing Spray 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JPW
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AH
MARINE/LONG TERM...RC