FXAK68 PAFC 061353
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
453 AM AKST Mon Feb 6 2023
.ANALYSIS AND UPPER LEVELS...
A strong low pressure system moving north across the Kenai
Peninsula is spreading snow over Prince William Sound and into
Bristol Bay. Bands of moderate to heavy snow have developed from
southern Cook Inlet to Homer and Seldovia this morning. Elevated
winds reaching high end gales continue around the low and also
with the front lifting toward the north gulf coast. A transient
ridge over the Alaska mainland meanwhile is providing quieter
weather for Southcentral with mid to high clouds passing overhead.
Out west, a complex low with multiple low centers is slowly
weakening and moving east. Colder air on the backside of the low
is aiding gusty northerly winds and convective snow showers over
the Bering Sea and Aleutian Chain.
Model guidance is in good agreement with the placement and
intensity of synoptic scale features at both the surface and in
the upper levels. As the aforementioned low weakens and winds
shift southwesterly, a chance of snow returns to Southcentral
today. Forecast confidence is high for snow coverage across the
Anchorage Bowl and Mat- Su Valleys lasting through early Tuesday.
PANC...Light winds will increase to southerly 10 kts with a brief
gust to 18 kts around 06th/14z. Snow will increase in coverage
with MVFR to IFR conditions from 06th/16z to 07th/03z. Vicinity
snow showers continues after 07th/03z.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Monday through Wednesday night)...
The well-advertised low is pushing onshore this morning, just west
of Seward. While colder air continues to wrap around the now
occluded low, a southerly flow near the surface has advected
enough warm air along the immediate coast east of the low center
to allow for a mix of rain and snow for Seward, Whittier, and
Portage. As the low continue to track inland and weaken, this flow
is expected to wane, allowing for a transition back to all snow.
On the backside of the low, however, enough colder air wrapping
around the center of circulation to allow for all snow across Cook
Inlet and Kachemak Bay. Deformation and instability along the mid
level trough west of the surface low is allowing for bands of
moderate to heavy snow to set up across Kachemak Bay this morning.
These bands will persist as they lift northward with the low
today, eventually overspreading the rest of the western Kenai
Peninsula, Anchorage Bowl, and Mat-Su Valleys. For areas around
Homer, a developing gusty southwesterly wind may also result in
some blowing snow, especially across the Homer Bluffs where the
resultant flow should allow for additional upslope snow.
As the low moves north, convergence in the southwesterly flow up
Cook Inlet and southeasterly flow through Turnagain Arm is
expected to develop. This may help enhance snow across the
Anchorage Bowl, especially across southern and western portions of
the Bowl. The development of a weak trough, along with an upper-
level wave and southwesterly flow, will also allow for widespread
snow to develop across the Susitna Valley this afternoon. Here,
snow may linger through Tuesday morning, especially in favored
upslope areas north and west of Talkeetna. Snow amounts of 1-3
inches are possible across the Matanuska and southern Susitna
Valleys with 2-4 inches, with locally higher amounts at elevation,
are possible across Anchorage. 3-5 inches of snow are possible
around Talkeetna with 6 to 10 inches of snow possible in the far
northern portion of the Susitna Valley.
For other areas, the southerly flow will result in continued
snowfall for the coastal mountains, as well as Valdez and
Cordova. However, with temperatures pushing into the mid 30s, rain
may mix in at times for Cordova. Southerly winds will be on the
increase across the Copper River Basin today as the low and its
decaying front move inland.
The widespread snow will taper off for Tuesday. However, weak
upper-level waves will continue to move north from the Gulf of
Alaska into Southcentral. This will result in scattered snow
showers, mainly along the southern half of the region. A weak area
of low pressure may move into Prince William Sound by Wednesday
morning with more widespread light snow for the Cook Inlet region.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
Broad longwave trough pattern lingers over Southwest Alaska,
slowly meandering eastward over the next couple of days.
Bristol Bay will stay light and showery with reduced visibilities
through the morning hours, with improving conditions into the
later afternoon hours. Snow chances will diminish but low stratus
clouds are expected to persist. Cold air wraps around the back
side of the trough, temperatures will continue to gradually drop
tonight through Tuesday night.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Northerly flow stretches across the Bering Sea. Cold air advection
will help enhance winds to small craft in some areas, with a band
of gale force winds across the Central Aleutians today. Heavy
freezing spray will continue to spread northern and eastern
Bering, nearing the Pribilof Island waters today. Extreme freezing
spray will be an issue along the ice edge as well over the next
couple of days. Light lingering snow showers will continue across
the Aleutian Chain and southern Alaska Peninsula through Tuesday.
.LONG TERM FORECAST (Days 4 through 7: Thursday through Sunday)...
Confidence continues to remain high on both domains remaining
rather active with no real sustained quiet stretches with high
pressure firmly in control, but rather transient ridges between
systems; the only exception might be coastal southwest Alaska.
Southern Alaska still remains under the influence of a broad
negatively trough. Expect more precipitation for the eastern
Kenai Peninsula, Prince William Sound, the northern Gulf Coast, as
well as interior southwest Alaska. The western Kenai Peninsula,
Anchorage, Mat-Su Valleys, and Copper River Basin could also see
precipitation chances during the first half of the longterm as
well, but uncertainty exists with potential cross barrier flow
issues. The models converge on the idea of a return to unsettled
weather as a deep Bering Sea low sends multiple fronts and
shortwaves eastward into the coast through at least Saturday. By
Sunday, there is a lot of model divergence at the surface, but the
consensus is that the longwave trough will continue to influence
MARINE...Storm Warning: 120
Gale Warning: 119, 125, 131, 172, 175, 176, 351
SYNOPSIS AND MODEL DISCUSSION...MF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM