Gale Warning 666, NWS Anchorage, AK

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

.ANALYSIS AND UPPER LEVELS...

An upper-level ridge extends from the Alaska Peninsula east to the
Panhandle with its axis located over the central Mainland. An
upper longwave trough follows in the wake of the ridge and
expands front west to east across the entire Bering Sea and
Aleutians Chain.

Clear skies over most of Southcentral early this morning will be
short-lived as a front approaches from the west and cloud cover
gradually spreads east. The strong surface front is currently
located over the eastern Bering and Aleutians, bringing with it
rain, snow, and high winds as it continues pushing onshore the
Southwest coast. Gale to storm force winds are currently located
over the eastern Bering, Southwest coast, and Alaska Peninsula.
Winds are especially strong through the gaps and passes of the
Alaska Peninsula, and a High Wind Warning is in effect for Port
Heiden through late this morning. Further west, the low associated
with the front is centered over the Bering Sea just northwest of
the Pribilof Islands.

&&

.MODEL DISCUSSION...

The primary model disagreement in the short term forecast is
still in regards to the low that develops near the western Gulf
coast Wednesday morning. Current GFS runs form the low center just
to southeast of Kodiak Island early on Wednesday morning, and
then the low tracks east into the Gulf through Thursday. On the
other hand, the NAM and EC form the low closer to the northern tip
of Kodiak Island (near the Barren Islands) early on Wednesday
morning, but these two models keep the low track snug along the
north Gulf coast through Thursday. The continued model
discrepancies with this low decrease forecast confidence for
precipitation type, timing and amounts for Southcentral.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist into this
afternoon. There is a chance for wind shear at 2000' beginning
around 20z today and lasting for roughly 5 to 6 hours. Starting
this evening, conditions are expected to drop down to IFR as a
front approaches from the west and increases chances for light
snow and reduced visibility.

&&

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

A pattern change is expected across Southcentral this week. Cloud
cover will increase through today as a front approaches from the
west. Snowfall is expected to begin over the Kenai Peninsula this
afternoon. Gusty southeasterly winds will increase through
Turnagain Arm this evening, however more southerly flow aloft will
help to counteract any downsloping effects in the Anchorage bowl
and a light snow accumulation of around half an inch is likely
before midnight. Precipitation will continue along the coast
through Tuesday likely falling as all rain or a light mix with
high temperatures approaching 40. Another front will move into the
Gulf by Wednesday. Precipitation looks to move inland through the
day, however uncertainty remains regarding the position of the
front's associated low which would affect precipitation type,
timing and amounts. However, inland areas would likely expect all
snow given cold enough air in the mid-levels.

&&

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

A strong front is moving into Southwest Alaska this morning as it
pushes into a robust area of high pressure to the east. Gusts up
to 80 mph have been observed along the Alaska Peninsula overnight
and will continue through the late morning hours before the front
and enhanced pressure gradient move into the Gulf. However,
elevated winds will linger through Kamishak Gap through the late
evening hours. A rapid increase in temperature has accompanied the
winds as warmer air aloft mixes downward and warm air streams in
from the North Pacific. Expected a mix of rain and snow along
coastal areas this morning before warm air moves in aloft and
quickly transitions precipitation to rain. This transition will
occur throughout all of Southwest Alaska from the coast to the
interior throughout the day. By late afternoon, snow levels along
the coast will range from 1,000 to 3,000 ft and up to 1,000 ft for
the more interior areas. Inland areas north of Dillingham are
expected to remain snow through the early afternoon, which will
allow for accumulations between 3 and 6 inches. Interior areas
that remain cooler may allow for areas of blowing snow,
particularly over elevated terrain, but most of the population
centers will remain too warm for blowing snow to reduce
visibilities.

The front will move through the region and into Southcentral
overnight, which will place Southwest into a showery regime.
Temperatures aloft will cool down again after frontal passage, but
onshore flow and remaining elevated winds will keep precipitation
type predominately rain through Tuesday morning. An additional low
will move into Bristol Bay later in the day Tuesday, likely
beginning as rain and transitioning to snow overnight as colder
air moves in aloft and surface temperatures cool. Areas north of
Iliamna and the Lower Kuskokwim Valley could see 3-6 inches out of
the system by Wednesday afternoon.

&&

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

A low currently west of the Pribilof Islands will move north into
the Chukchi Sea through Tomorrow morning. Behind the low, cooler
air aloft will move in from the west, placing the Bering Sea and
Aleutian Chain into a showery regime. A few weak shortwaves
passing through will enhance areas of winds up to gale force, but
overall conditions will remain on the calmer side. An stronger
system will move north into the Chain Wednesday afternoon,
bringing another round of Gale to Storm force winds and rain.

&&

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

Similar to the past day or so, model agreement starts out very
good at the start of the period on Thursday, but solutions again
diverge significantly heading towards the weekend. To start things
off on Thursday, three synoptic systems will be in play looking
from east to west across the outlook area. On the east side, an
upper trough and and attendant surface low will be drifting east
across the Gulf, focusing areas of rain and snow across
Southcentral on Thursday predominantly along the northern Gulf
coast. The second system will be a large gale to low-end storm
force low moving along or just south of the Aleutians, sending
gusty easterly winds and mainly rain across the Aleutian Chain
through at early Friday. The third system will be approaching the
western Bering by Thursday afternoon as it progresses east out of
Kamchatka.

As alluded to above, the finer scale details of the pattern begin
to blur looking from Friday onwards. The GFS has been a stubborn
outlier with the track of the larger, stronger low moving south of
the Aleutians compared to other solutions by Friday, with recent
runs still attempting to push most of the low straight east and to
the south of the Gulf as the entire system begins to weaken and
fill in. Both of the other global model solutions show the low
pivot more northeast, or straight into the central/eastern Bering
before stalling out in place through at least Saturday. These
differences significantly affect the potential wind field across
the Bering, while also playing a role in how the next item of
interest evolves towards the end of the forecast period.

The signal for a strong, blocking ridge to develop by Saturday
and Sunday is getting quite a bit stronger in today's model runs.
Both ensemble guidance and operational solutions are better honing
in on the potential for an Omega block ridge to develop over
Alaska and northwest Canadian provinces next weekend, while a
longwave trough stalls out to the west over the Bering and
Aleutians. This is increasing confidence for an extension into at
least Sunday of the already warmer than average temperatures
returning earlier on in the week across the southern mainland. The
most favored area for heavier precipitation with this pattern
developing will be focused over Southwest and along the Alaska
Peninsula, where strong southerly flow and moisture will stream
north between the Bering trough and blocking ridge to the east,
with mixed precipitation likely persisting across this area for
multiple days towards the end of this week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning: 161.
		 Winter Weather Advisory: 161.
	     Coastal Flood Advisory: 155.
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...AF
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CJ
LONG TERM...AS