Gale Warning 260, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
543 AM AKDT Wed Mar 16 2022

.ANALYSIS AND UPPER LEVELS...

Long wave trough pattern encompasses much of the State today as a
polar low traverse southwards towards the southern Alaska
Peninsula before pivoting into the Gulf. A swath of cold air is
pulled southwards with the system across the Bering, resulting in
gusty winds across the Eastern Aleutians, Pribilofs, and areas
south of the AKPen. Clouds have rolled in over pretty much all of
Southcentral and have started spilling over into Southwest as a
front pushes northwards into the Gulf. Precipitation has reached
much of Southcentral and far eastern portions of Southwest,
however, cross-barrier flow in the upper levels is keeping
downslope areas such as Anchorage and Kenai dry today.

&&

.MODEL DISCUSSION...

Models are in good overall synoptic agreement through the short
term. There is, however, a good amount of discrepancy with a
North Pacific low moving towards the Gulf Friday and Saturday. The
most recent model runs show the NAM as the biggest outlier,
placing it further west initially than the other solutions. Model
spread increases as we reach Friday night, with weak agreement on
center location, but an overall solid handle on the speed of the
system for the NAM/EC/Canadian through Saturday morning. The GFS
seems to be lagging behind and cycling more slowly in the North
Pacific before meandering into the Gulf.

&&

.AVIATION...
PANC...Expect conditions to become mostly IFR by mid-morning with
brief periods of marginal conditions scattered throughout the
day.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Today through Friday
Night)...

A surface low near Afognak Island is circulating quite a bit of
Pacific moisture into the coast this morning. Snow is currently
being reported even down to sea level in Seward, Whittier and
Valdez. The snow has changed over to rain in Cordova, and all rain
is falling in Kodiak. This same pattern will persist into tonight.
Expect continued nearly continuous snow across the mountains. For
Seward and Whittier, daytime heating and continued onshore flow
should result in some mixing or changeover to rain today. Valdez
should be sheltered enough to remain all snow.

Tonight a low over the central Gulf will shift the rotational
focus. A disturbance will circulate around the upper level low
over the Alaska Peninsula. This will cause a surface low to
develop and track north over the central Gulf towards the Coast.
This will give Kodiak a brief break in the precipitation as the
winds go slack. As the disturbance approaches mainland
Southcentral, snow will break out over the Western Kenai
Peninsula from south to north. It will begin around Homer late
this evening, move to the Kenai-Soldotna area early Thursday
morning, then move into Anchorage and the southern Susitna Valley
around sunrise Thursday. Light snow may persist into the early
afternoon. The disturbance will shift westward as it moves around
the upper level low Thursday afternoon and evening, so little if
any precipitation is expected in the Mat-Su. The eastern side of
this disturbance may also result in some light snow overnight
tonight into Thursday morning across the Copper River Basin. Any
accumulations will be minor.

On Thursday night, conditions return to much the same as they are
now, with onshore flow continuing snow across the eastern Kenai,
and relatively little precipitation elsewhere, especially from
Anchorage north, which are likely to remain entirely dry. A new
North Pacific low moves into the southern Gulf on Friday. Its
leading front will move into the coast, resulting in heavier
precipitation through the day. However, since the front is
occluded and heavily wrapped around the surface low that will
remain largely stationary over the southern Gulf. Thus, the front
will not have any forward momentum to spread any precipitation to
inland areas.

By Friday night, the low will gradually drift north, which will
turn the predominant flow eastward. This will focus any onshore
precipitation upsloping against the mountains into Whittier and
Portage Valley, with much less precipitation towards Seward and
Valdez, as the winds become more parallel with the coast.

&&

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

Cold air temperatures associated with an upper low ranging
from -16 to -24 degrees Celsius at 850 mb advects south of the
Kuskokwim Delta this morning, causing fresh to strong winds with
higher gusts over Kuskokwim Delta today. The upper low will
continue to enhance steady light snow over much of the Kusko Delta
Coast and farther inland today. Meanwhile, a low lingering near
Shelikof Strait this morning will produce increased clouds and
moisture extending west of the Alaska Range through the Kusko
Delta Coast through tonight. These combined patterns could bring
1 to 3 inches of snow in most populated areas from Iliamna to
Dillingham as well as King Salmon, while areas of light snow will
continue through Thursday but will diminish through the day. Winds
will gradually diminish by Thursday afternoon as the pressure
gradient relaxes. On Friday an upper low originating from Siberia
will bring increasing winds for the Kuskokwim Delta and chances of
snow showers across the area and will reinforce the cold air.

&&

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

Cold polar air combined with an upper ridging over the western
Bering will reinforced gales over the central Bering/Aleutians
through at least Thu night and for the eastern Bering through Fri
night. A stacked low near the Alaska Peninsula tonight will aid to
stronger gap winds and increased cloudiness and snow showers for
the central/eastern Aleutians and south of AKPen into Thu evening
and potentially through Fri. Overall, an unsettled weather pattern
will persist for much of the region through the short term.

&&

.Marine (Days 3 through 5: Friday through Sunday)...

Gulf of Alaska: A well developed low and its front moves across
the Gulf through Sunday. Forecast models in good agreement.
Widespread high end gales around the low moving across the Gulf
and through the Barren Island and Kamishak Bay, diminishing
Sunday. Seas building to 18 feet for Saturday, subsiding Sunday.
Some freezing spray is expected South and West of Kodiak Island
for Saturday.

Bering Sea: Arctic high pressure moves across the Western Bering
abutting low pressure over Interior Alaska through Sunday.
Forecast models in good agreement. Gusty Northerly winds over the
Central and Eastern Bering increases to widespread high end gales
and extending across the Aleutians and Alaska Peninsula Saturday
through Sunday. Seas building to 18 feet along the Bering side of
the Aleutians and Alaska Peninsula for Sunday. Heavy freezing
spray expected over Central and Eastern Aleutian open waters. A
strong central North Pacific low brings gusty Southeasterly winds
to the Western and Central Aleutians Friday and Saturday. Seas
building to 20 feet along the Pacific side of the Aleutians
through Sunday.

&&

.Long Term Discussion (Days 4 through 7: Saturday through Tuesday)...

The latest operational model runs are in fair agreement with the
evolution and progression of the synoptic scale features, but
diverge in the specific details towards the end of the period. The
main synoptic features on Saturday will be an upper level low in
the central Gulf, while another low moves south of the Eastern
Aleutian Islands. Even though there is uncertainty regarding the
interaction of these two features, the GFS/EC/CAN and ensemble
means form a broad longwave trough extending from the North
Pacific to the Gulf of Alaska.

From Sunday and beyond, there is considerable spread with the
next system moving towards the Bering Sea. The GFS seems to be the
outlier in cutting off a deep low south of the Aleutians, while
the EC/CAN keep the main low well to the north. Nonetheless, there
seems to be a general consensus that a southerly flow pattern
will push a series of shortwaves and associated surface lows
northward. Confidence is moderate that precipitation will be
concentrated through the Panhandle and up into the southern
coasts. Much of the mainland should be relatively dry during the
period, with the exception for potential snow showers by this
upcoming weekend in the eastern interior. Otherwise, temperatures
are expected to be below normal across the coastal areas and
interior valleys as a general troughing pattern stays firmly
anchored over the entire Alaska mainland.

Out west, a ridge of high pressure will build across the Bering
Sea. A reinforcement of cold air advection will help drive
northerly winds funneling through the gaps and passes of the
Alaska Peninsula and Eastern Aleutian Islands. Wrap around
moisture on the backside of the aforementioned upper low will
bring occasional snow showers into these regions later this week.
A drying trend commences on Monday as the ridge axis shifts over
the western mainland, while a gale force front extending from a
Kamchatka low moves slowly east across the Western/Central
Aleutians.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 119 130 155 172 181 185
		 Heavy Freezing Spray Warning 140 150 155 160 165 179 180 185 412 414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KM
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
MARINE/LONG TERM...KZ/MF