High Wind Watch 7, NWS Anchorage, AK

915 
WWAK71 PAFC 040046
NPWAER

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
346 PM AKST Tue Nov 3 2020

AKZ131-041400-
/O.UPG.PAFC.HW.A.0007.201105T0600Z-201105T1800Z/
/O.NEW.PAFC.HW.W.0013.201105T0600Z-201105T1800Z/
Northeast Prince William Sound-
Including the cities of Valdez and Thompson Pass
346 PM AKST Tue Nov 3 2020

...HIGH WIND WARNING IN EFFECT FROM 9 PM WEDNESDAY TO 9 AM AKST
THURSDAY THROUGH THOMPSON PASS..

* WHAT...Northeast winds 40 to 55 mph with gusts up to 75 mph 
  expected.

* WHERE...THOMPSON PASS.

* WHEN...From 9 PM Wednesday to 9 AM AKST Thursday.

* IMPACTS...High winds may move loose debris, damage property, 
  and cause power outages. Travel will be difficult, especially 
  for high profile vehicles.

* ADDITIONAL DETAILS...In addition to the winds, very cold
  temperatures will also accompany the wind bringing wind chill
  values as low as 30 below zero. Wind gusts up to 50 mph are
  expected in the town of Valdez.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

People are urged to secure loose objects that could be blown
around or damaged by the wind. Prepare for the possibility of
widespread power outages. Use caution if you must drive.

&&

$$

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

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 PM AKST Mon Nov 2 2020

.ANALYSIS AND UPPER LEVELS...

An upper-level low over Prince William Sound continues to keep
arctic air in place across much of the Southern Mainland today.
Afternoon temperatures range from -10 in parts of the Copper
River Basin to the teens and 20s elsewhere. The highest
temperatures this afternoon correspond to the locations seeing the
strongest winds, both the northerly gap winds across Southcentral
and the northerly winds along the Southwest coast. The winds have
started to come down a bit from their peak earlier this morning,
but are still quite gusty. Palmer and Thompson Pass saw peak gusts
of 72 and 73 mph, respectively. Skies are mainly clear across the
region, but there is some cloud cover across Prince William Sound,
spreading north over the Copper River Basin. This is due to a
surface low spinning east of Middleton Island. Snow showers are
pinwheeling around the center of circulation and have occasional
moved over Cordova.

Satellite also shows banded cumulus clouds from the eastern
Bering to the AKPEN and eastern Aleutians, indicative of the
continued cold air advection from the mainland. Snow showers are
also present with these clouds and extend from Saint Paul down to
Cold Bay. Temperatures are slightly warmer along the rest of the
Chain with rain mixing in for Dutch Harbor.

&&

.MODEL DISCUSSION...

Synoptic models remain in good agreement through the short term.
Thus high-res models remain preferred to resolve the continued gap
winds over Southcentral and the developing northwesterly winds
across Bristol Bay and the AKPEN for late Tuesday into Wednesday.
There is some discrepancy between the models concerning the
evolution of the surface low in the northern Gulf late tonight
into Tuesday. The NAM continues to be the stronger of the
solutions, but all are fairly clustered and show this feature
moving onshore east of the Copper River Delta by early Wednesday
morning. Either way, this would enhance the strong pressure
gradient near the coast and thus subsequently maintain the
northerly gap winds, particularly in the Copper River Delta
through midweek. By midweek, the trough over the Gulf remains
as does the winds, albeit a tad weaker. Guidance is also well
clustered around a storm-force low along the eastern Russia coast
pushing a front over Southwest Alaska. Models have slowed its
forward progression by early Thursday from previous runs as it
runs into the ridge over the interior. Nonetheless, guidance is
keying in on a pattern change for the Southern Mainland by the
end of the week.

&&

.AVIATION...

PANC...VFR conditions will persist. Northerly winds will continue
an overall weakening trend tonight through Tuesday as pressure
gradients relax.

&&

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

The sunny, dry, and very cold pattern for early November standards
continues for Southcentral the next few days. The main issues
will be the low temperatures for tonight throughout Southcentral.
High level clouds are currently moving in overhead and with the
winds remaining gusty this will make for a particularly tough low
temperature forecast tonight. Peak wind gusts throughout Anchorage
were between 35-45 mph with Elmendorf Air Force base reporting 66
mph early this morning. The Matanuska Valley also had very strong
winds with a peak wind gust in Palmer of 72 mph earlier today.
Winds will continue to gradually diminish tonight but will remain
gusty through the day Tuesday especially for the Matanuska Valley
and West Anchorage. Due to the wind expected to stay up across
much of Southcentral and increasing cloud cover for the overnight,
temperatures aren't expected to fall as low as they otherwise
would if it were clear and calm.

After the winds fully diminish later in the day on Tuesday, the
very cold temperatures will be the main concern for Tuesday night
and Wednesday night as decent radiational cooling is expected. As
a result, the coldest mornings of the season are possible
Wednesday and Thursday morning across Southcentral.

Further south across Kodiak Island, models are depicting a fairly
strong upper level wave moving swiftly to the south and east
Tuesday evening into Wednesday morning. This is expected to bring
the southern Kodiak Island area a quick burst of snow during the
aforementioned time period. The greatest threat for this continues
to be across southern Kodiak Island but brought slight chance onto
the doorstep of Kodiak city just in case this ends up slightly
further north. Most likely outcome at this time is Kodiak city
remains dry.

Lastly, a pattern change is expected for late this week into the
weekend. A frontal system moving eastward from Southwest Alaska is
expected to bring increasing clouds to the region Thursday with
increasing precipitation chances in the form of light snow with
rain for Kodiak.

&&

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

An active weather pattern is expected across Southwest Alaska over
the next few days as a shortwave trough moves in from the
northwest on Tuesday, bringing a quick hitting snow to the
Kuskokwim Delta. The main concern is behind this trough, brisk
northwesterly flow will promote strong cold air advection over the
warmer sea surface temperatures as it is early in the season. This
synoptic set up is ideal for Ocean Effect Snow due to at least a
13-15 Celsius temperature difference between the surface and
850mb. Straightline flow with little to no directional shear in
addition to the instability will allow for these snowbands to
form. These snowbands will produce heavy snow at times while windy
conditions persist along the coast. This means that visibilities
will become significantly restricted with some coastal locations
expected to have visibility reduced to a quarter mile or less at
times. These Ocean-Effect snow bands are expected to taper off
Wednesday morning as the winds veer southwesterly.

Another concern is the potential for coastal flooding along the
Kuskokwim Delta and Bristol Bay Thursday afternoon. Strong
southwesterly flow associated with a frontal system will promote
strong onshore flow. Latest ETSS Guidance suggests areas in the
Kuskokwim Delta could potentially see water levels 5ft above
Highest Astronomical Tide. This is still quite a ways out in time,
so for now will just keep an eye on this storm and see if the
current track and timing hold. If so, will likely need to issue
some sort of product as we get closer.

&&

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

An active weather pattern is expected across the Bering/Aleutians
over the next 3 days as strong northwesterly flow promotes cold
air advection over the warmer sea surface temperatures of the
eastern Bering Sea. Latest ASCAT pass shows this northwesterly
flow reaching gale force south of the eastern AKPEN (just west of
Kodiak Island). This synoptic set up is ideal for Ocean-Effect
Snow as there is a 13-15 Celsius difference between the surface
and 850mb with straight-line flow with little to no directional
shear. The lack of wind shear is favorable for Ocean-Effect snow
bands to form. These Ocean-Effect Snow bands will be over the
eastern Bering/Aleutians and the AKPEN. In addition to the Ocean-
Effect snow, strong northwesterly winds are expected. These winds
will reach storm force and gust to hurricane force through the
gaps between the eastern Aleutians and along the AKPEN Tuesday
night into Wednesday morning. Other areas that will experience
local storm force winds from funneling northwesterly winds are in
Etolin Strait and along Cape Newenham.

The second feature of concern during the forecast period is a
front entering the western Bering/Aleutians Tuesday night. Gale
force southerly winds will develop along the western
Bering/Aleutians Tuesday night and increase to storm force
Wednesday morning. This front will continue eastward while
gradually weakening. Gale force winds associated with this front
will reach the central Bering/Aleutians Wednesday night and then
reach the eastern Bering/Aleutians Thursday afternoon.

&&

.MARINE (Days 3 through 5/Thursday through Saturday)...

A strong Kamchatka low will push a front across the Bering
Thursday. Southwesterly storm force winds and seas up to 30 feet
are expected across the Bering early Thursday before winds
diminish to gales late Thursday. As this Kamchatka low weakens
Friday, winds will diminish to small craft levels. Another low
arrives over the western Aleutians Saturday bringing the
potential for gale force winds.

For the Gulf, gusty northerly outflow winds are expected early
Thursday especially over the Barren Islands. Winds will shift
to southwesterly Friday for the western Gulf especially through
Shelikof Strait as a ridge strengthens over the Gulf for the
weekend. Southerly gale force winds may return to the western
Gulf waters by Saturday as a North Pacific low lifts northward
near Kodiak Island.

&&

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

Two key features that have been consistent for the long term
forecast include an upper level low over the Kamchatka Peninsula
and a strong upper level ridge maintaining its hold over the Gulf
of Alaska. Active weather is expected for southern Alaska for the
start of the weekend as a North Pacific low lifts northward and
attempts to suppress the persistent Gulf ridge to the south. As
this low moves into the Bristol Bay region early Saturday, a
strong pressure gradient between the incoming low and the
persistent high will generate gusty southerly winds across the
western Gulf waters and Kodiak Island. Additionally, there is
potential for a wintry mix of precipitation for interior Bristol
Bay and the Middle Kuskokwim Valley as this low lifts northward.
Depending on the track of this low, wintry precipitation is also
possible for Southcentral Saturday and Sunday. Model solutions
continue to change with regard to where this low tracks, so
confidence remains low at this time. By Sunday, an upper level
low builds in across much of the state, ultimately displacing the
persistent upper level ridge to the south. Farther west, a strong
Kamchatka low develops late Saturday and pushes a front across
the Bering Sunday. Right now, an active weather pattern looks to
persist through the start of the next work week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 155.
MARINE...Storm Warning 150 178.
 Gale Warning 127 130 131 132 140 155 160 165 177 180 181 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...TM
SOUTHCENTRAL ALASKA...MV
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...KO