Gale Warning 706, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
423 PM AKST Mon Nov 7 2022

.ANALYSIS AND UPPER LEVELS...
The high amplitude upper level ridge is now over the eastern
Copper River Basin and continues to edge eastward as the large
low in the Bering Sea takes control of the weather over the state.
The surface low is near St Lawrence Island as of early this
afternoon with the front associated with it over the Bristol Bay
region and Kuskokwim Valley. This front extends quite far south to
about 25N latitude, so the air advecting northward along this
front has a very warm temperature tap with it. Equally impressive
is the cold air pouring southward along the west coast of north
America as seen on satellite which is reaching to about 30N. Now
back to Alaska: The front that battered southwest mainland Alaska
is now weakening as it moves eastward. This Low and front is the
big pattern changer that we have been expecting to bring more mild
temperatures to southern ALaska through the rest of the week and
into next week.

&&

.MODEL DISCUSSION...
The overall forecast challenge is in the Gulf of Alaska and
SOuthcentral region and tied to the development and movement of
that triple point low near Kodiak on Tuesday. Models are getting
into better agreement overall, but the farther south track of the
GFS would limit the amount of precipitation in Anchorage and keep
Anchorage and most of the Kenai Peninsula cooler. The immediate
issue is whether the Turnagain Arm winds move over the Anchorage
Bowl tonight and bring in the associated warmer air.

&&

.AVIATION...
PANC...The forecast is very much dependent of what happens with
the surface winds and whether they remain from the north or if
Southeasterly winds off of Turnagain Arm over the airfield. At
this time it does look more likely the Southeasterly winds will
make it to the terminal this evening through the overnight hours.
This will limit the snowfall and keep the ceiling heights from
getting to MVFR conditions. Should winds remain from the north at
the surface there would likely be lower ceilings and visibilities
in snowfall this evening, but the TAF reflects the expectation for
southeast winds. By Tuesday morning, the winds should switch to
northeast, but the chance for precipitation will be minimal by
that time.

&&

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

An active weather pattern is in store for Southcentral Alaska
over the next couple of days. A frontal system will move through
tonight and bring the first round of precipitation to the region.
A triple-point low is forecast to develop east of Kodiak Tuesday
evening and move northeastward and bring a second round of
precipitation Tuesday night into Wednesday. The biggest forecast
challenge continues to be precipitation-type. For the Anchorage
Bowl, Matanuska Valley and Susitna Valley, snow is the most likely
precipitation type as these locations are expected to remain
north and west of the low center combined with the warmest
forecast soundings show a shallow warm layer near the surface. Due
to this synoptic setup combined with the forecast soundings, the
warmest scenario appears to be snow with surface temperatures a
couple of degrees above freezing due to a deep cold layer aloft.
The biggest challenges for precipitation-type are throughout the
Kenai Peninsula and coastal locations. One area where there is
higher confidence is that this set up is unfavorable for freezing
rain due to the lack of cold air damming at the surface with a
shallow warm layer aloft.

The other part of the story will be the strong winds throughout
the mountains and in Turnagain Arm. The stronger NAM/NAM Nest
solution was favored in this forecast due to the current wind
observations across Southwest Alaska. Gale force winds with storm
force gusts are likely in both of these locations this evening
through Wednesday night.

&&

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

A strong front stretching south-to-north across Southwest Alaska
pushes eastward across the Alaska Range tonight. Warm south-to-
southwesterly flow has led to temperatures warming into the upper
30s this afternoon, turning much of the precipitation across the
region to rain from snow. Strong, gusty southerly winds will
gradually diminish this evening as the front exits the region.
Precipitation along the front also comes to an end from west to
east tonight, with only light showers expected in its wake.

A deep upper-level trough over the Bering Sea draws a shortwave
north across the Alaska Peninsula tonight, bringing another round
of precipitation to the region Tuesday morning. This renewed
precipitation should begin as rain for most locations, though
temperatures aloft will cool down again Tuesday afternoon with the
trough axis shifting eastward and a weak low developing in Bristol
Bay. This will allow for a transition to snow overnight as cooler
northwesterly flow moves into the region. Areas north of Iliamna
and the Lower Kuskokwim Valley could see 3-6 inches out of the
system through Wednesday afternoon. Temperatures continue to
decline for Wednesday night and Thursday as this second system
exits the area. A ridge out ahead of a strong low entering the
Bering will move into Southwest Alaska on Thursday, leading to
drier conditions and clearer skies.

&&

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

A low pressure system tracking into the Bering Strait this evening
will push cooler air aloft across the Bering Sea from the west,
leading to showery conditions across the region through Tuesday
night. A few weak shortwaves passing through will enhance areas
of winds up to gale force, but overall conditions will remain on
the calmer side. A stronger low approaches the western/central
Aleutians on Wednesday, bringing gale force winds and moderate-
to-heavy rain. Its front reaches the eastern Aleutians and the
Pribilof Islands with gales and rain by Thursday morning as the
low center tracks just south of the Aleutian Chain.

&&

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

The pattern will start out on Friday with a very large low
centered over the eastern Bering, with cyclonic upper flow
extending well away from the center across most of the Aleutians
and over Southwest. A broad small craft to gale strength wind
field should be affecting much of the same region at the surface,
along with precipitation mainly in the form of rain across the
Aleutians. More of a mix of rain and snow will be likely along the
low's front as it moves into Southwest during the day on Friday.
Another low is set to be moving into the western Bering/Aleutians
by this point in time as well, which will begin to merge with the
initial system and reinforce deep troughing over the Bering
through at least Saturday. Meanwhile, things should be starting
out fairly quiet over Southcentral, where a sharp upper ridge will
initially be in place. However, this ridge axis will begin to
shift east with time, allowing heavier precipitation and strong
south to southeast flow to spread into the eastern Kenai
Peninsula and Prince William Sound region by late Friday into
Saturday.

From the rest of the weekend into early next week, models continue
to signal the development of a blocking pattern over the Alaska
region. The aforementioned upper ridge is currently projected to
strengthen dramatically northwest Canada and mainland Alaska
through Monday, becoming a robust Omega block. This should cause
the upper trough/low upstream over the Bering to stall in place,
perhaps eventually pinching off into a cutoff low as another
strong ridge builds into the western Bering on Monday. The most
active weather during this stretch will be focused where deep,
persistent southerly flow pushes into the coast, or along the
Alaska Peninsula, across Kodiak Island and over portions of the
northern Gulf coast, where precipitation will be greatly enhanced
by onshore and upslope flow. Very warm temperatures compared to
average are likely across nearly the entire eastern half of the
outlook area for this timeframe as warm, moist air is forced north
around the blocking high. Daytime temperatures in the 30s to 40s
are likely across even some more interior valleys of Southcentral
and Southwest from Saturday to Monday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning: 160, 165, 180.
 		 Gale Warning: 130-132, 136, 139, 150, 155, 177, 178, 181,
					   185, 352, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...ED
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CQ
LONG TERM...AS