Small Craft Advisory 253, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKDT Fri Mar 24 2023

.ANALYSIS AND UPPER LEVELS...

The 500 mb low is centered over northwest Alaska this afternoon
and the rotation around this feature can be seen well on the GOES
satellite loop. The front that extends out of the low can also be
seen over the Interior of the state and then dropping over
Southcentral Alaska and bending back into Southwest Alaska. This
front is the source of the snow that developed from the northern
Susitna Valley and over the Talkeetna Mountains as well as over
the Chugach and Kenai Mountains this afternoon. This wave is
moving quickly eastward so the snow should be over in these areas
and just producing a few snow showers over the Copper River Basin
by the time you read this.

The upper level trough is lagging the front some and this will
keep some snow in Southwest Alaska into the evening. Strong,
westerly, cross-barrier flow can be seen across the Aleutian
Range from the Alaska Peninsula through Shelikof Strait and
across Kodiak Island with the washboard pattern of clouds that
are mainly stationary as seen on the satellite loops. In the far
western Bering Sea near the Kamchatka Peninsula is a strong low
that is bringing strong southerly winds and rain the the western
Aleutians due to its front. This low and front is the one that is
moving eastward and will be the source of the challenging weather
in the Bering Sea and Southwest Alaska this weekend.

&&

.MODEL DISCUSSION...
Models are in good synoptic agreement into next week. the biggest
model issues occur in the next 12 hours as the upper level trough
passes across Southcentral. About half the models, including some
of the hi-resolution ones, are enhancing the lift over Cook Inlet
and bringing in a shot of more snow showers late this evening
while the other half have mostly clear conditions. By the time we
get to tomorrow, models seem to be in better agreement with all
the meaningful features.

&&

.AVIATION...
PANC...
The gusty southerly winds will turn more westerly and then diminish
this evening. Saturday should see a light northerly wind. After
some MVFR conditions this afternoon, ceilings should lift to VFR
and remain VFR through Saturday.

&&

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

Snow showers will mainly linger near higher terrain of the
western Chugach, Kenai mountains, the Talkeetna Mountains through
this evening before moving east tonight. A ridge of high pressure
will build in Saturday and while it means no precipitation,
outflow winds through gaps and northwest turning northerly flow
will accelerate through terrain gaps. Cold air advection that
helps to reinforce the winds will be brief and should decrease
later on Saturday for the western slopes. Winds will likely remain
strong near Valdez and Cordova until Sunday morning. The weather
should remain relatively quiet through the rest of the weekend as
the ridge continues to build on Sunday, but the next system due to
Southcentral will be towards Tuesday.

&&

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

A weak low and subtle shortwave have moved into Bristol Bay this
afternoon on the south side of a deep upper trough moving over the
Interior, with light to moderate snow now following this system
east. Most of this activity will end from west to east across
Bristol Bay later this evening as the upper trough shifts towards
Southcentral and as a strong upper ridge moves into place from the
Bering Sea. A pronounced warming trend will commence not long
after this batch of snow clears out on Saturday as the ridge axis
continues to move east and as a belt of deep, strong southwest
flow begins to transport a much warmer air mass inland. Aside from
the most interior valleys over the Middle Kuskokwim, temperatures
will likely push above freezing by Saturday afternoon as warm air
continues to stream northeast across the region.

By Saturday afternoon and evening, a strong front moving steadily
east across the Bering will begin to impact the Kuskokwim Delta as
strong southerly winds pick up along the coast as steady
precipitation moves into the area from west to east. Low level
temperatures pushing above freezing should be enough for mainly
rain to fall at the onset, perhaps mixed with very wet, slushy
snow at times. The front will slow down considerably between
Saturday night and Sunday, resulting in prolonged, steady rainfall
adding up to as much as 1 inch across portions of the Kuskokwim
Delta by the end of the day oh Sunday. Rain or rain/snow mix will
gradually spread into western parts of Bristol Bay and the Middle
Kuskokwim Valley, but the highest amounts and intensity will be
concentrated over the Y-K Delta near the almost stalling front. By
Sunday night and Monday, the front will finally begin to
accelerate east as much colder temperatures also move back in
behind the frontal passage. There is still some potential for a
few inches of snowfall near the back edge of the precipitation
shield before everything dries out, with this potential again
looking highest over parts of the Kuskokwim Delta Sunday night
into early Monday.

&&

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

Warm, wet and windy will be the name of the game for most of the
region as a strong front moves into the western Bering tonight and
proceeds to take quite a bit of time to make it across to
Southwest over the next few days. Storm force winds and rain
remain expected across the far western Aleutians this evening,
with a few gusts peaking near 70 mph remaining possible until
later tonight as winds decrease behind the frontal passage. The
front will weaken as it steadily moves west into the central
Aleutians and Pribilofs on Saturday, with steady rain and
southerly winds up to gale force shifting east ahead of the
boundary. The front will nearly stall out along a line running
between the Pribilofs and central Aleutians on Sunday, resulting
in a prolonged period of steady rainfall adding up to as much as 1
inch of liquid for places including St George and Atka by the time
the front finally pushes farther southeast on Sunday night. Calmer
and drier conditions will briefly return as the front clears the
Aleutian Chain and upper ridging moves over the Bering on Monday,
but the next low will be near on the horizon as it approaches the
western aleutians with more southerly winds and rain by Monday
evening.

&&

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

The weather pattern on Tuesday will start off with weak high
pressure over Southern Alaska and a moderately strong low in the
central Bering Sea. As this low moves eastward on Wednesday, it
will bring some snow into Southwest Alaska which will already be
in an airmass cold enough for snow and areas of rain and snow to
Southcentral Alaska. As the rest of the week progresses, the upper
level low will broaden and encompass most of mainland Alaska. The
surface low should track to Southwest Alaska by Thursday with a
triple point low developing near Kodiak on Thursday as well. The
low is not expected to move much between Thursday and Friday as
the upper level energy to feed int and move it along will be well
south of the area. This will lead to, seasonal temperatures and
generally cloudy skies with some scattered snow showers across
Southwest and Southcentral Alaska Wednesday through Friday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 786 787 411.
		 Gale Warning 710 711 712 721 759 763-767 772 781 784 785
					  412-414.

FIRE WEATHER...NONE.

&&

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