Gale Warning 599, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
504 PM AKDT Fri Oct 7 2022

.ANALYSIS AND UPPER LEVELS...

An upper trough is currently digging moving a cross the western
Bering Sea. The jetstream currently extends northeastward from
Japan through southern Yukon Territory.

Closer to the surface, radar imagery shows rain and showers
moving northeastward across the Gulf of Alaska and across
Southcentral Alaska. The bulk of the rain is moving northeastward
across the Gulf into eastern Prince William Sound and points east.
Showers are moving northeastward across Cook Inlet into
Southcentral Alaska.

&&

.MODEL DISCUSSION...

Guidance is starting to show more run to run consistency in the
track of the next Bering Sea low that is expected to move over
Southwest Alaska. The current track has shifted considerably to
the south compared to 24 hours ago. ETSS guidance is hinting at
the potential for coastal flooding across western Bristol Bay,
however there is still a large variance between ensemble members,
thus confidence is only moderate at best for now. Models also show
agreement with 850mb temperatures falling below zero on Sunday
morning during the last portion of precipitation for Southcentral.
This means there is a chance for snow on the Upper Hillside Sunday
morning and early afternoon. Confidence is low with respect to
amounts as there is a lower confidence to where the exact snow
level will set up.

&&

.AVIATION...
PANC...Conditions will be VFR but may occasionally drop to MVFR overnight
and tomorrow morning. Southeasterly Turnagain Arm winds are
expected to ease tonight and will return tomorrow morning. There
is a low chance that 35 knot gusts will occur tomorrow afternoon.

&&

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

The main weather story for today is the front approaching from
the west. This is turning southwesterly flow aloft with a short
wave propagating over Cook Inlet and into the Prince William
SOund areas. Over the Sound it is tapping into a very moist plume
associated with a low well south of the Gulf, but that combination
is bringing in a band of heavy precipitation to the COrdova area
early this morning. This area of rain will not move much today as
it will have its westward motion stopped by the incoming front
from the west. Rain over the Susitna Valley and Cook Inlet areas
is associated with that front, but there is not really a lot of
reinforcing moisture past that initial push until the upper level
trough really digs in later this weekend. therefore, the rain
over for Cook Inlet including the Anchorage area will be early
this morning and then just a chance of rain.

The weather gets a little more interesting as that upper low dig
southeastward and the big push of moisture and lift moves over
Southcentral. That should come in Saturday morning from west-to-
east and bring in widespread rain. The big question will be
whether there will be enough cold air moving in before the rain
stops to change that rain into snow Saturday night into Sunday. It
still looks unlikely for that to occur at sea level especially
with 850 mb temperatures remaining at or above 0C until Sunday
morning. This is due to the way the upper low will track over
Kodiak Island on Saturday night which will keep the warmer air in
place over Southcentral for longer as the warm sector remains over
the mainland areas. By late Saturday night into Sunday morning
the colder air will probably bring snow level down to 1500 ft to
2500 ft across the area. This will mean that places such as
Turnagain Pass, Chickaloon Pass, Broad Pass and the Anchorage
Hillside are likely to see some snow. Places lower in elevation
that than will likely remain rain. Seward is looking at a bit if
rain with somewhere around 3.5 inches of rain from late Friday
night through Sunday morning.

&&

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

Scattered showers continue through Southwest Alaska. A trough
digging south through the Bering will bring additional
precipitation to beginning late Saturday through and taper off
Sunday. Rainfall totals of around an inch look to be most likely
in the Bristol Bay area and the Middle Kuskokwim Valley with
higher totals near terrain. Cold air and gusty winds will usher
into Southwest behind the trough Saturday night. Overnight lows
this weekend could hit below freezing with the coolest morning
expected to be Monday. Outside of the mountains, initial
precipitation is expected to be rain, but as temperatures cool,
snowflakes could mix. The Middle Kuskokwim Valley may fully
transition to snow Sunday morning and higher elevations should see
some snowfall. Sleetmute could see two inches or less.

A break from the winds and precipitation is possible later on
Sunday, but a strong, storm force low is tracking across the
Bering Sea Monday. Confidence is increasing for the likelihood of
storm surge and potential coastal flood and erosion, possible for
the entire Southwest Coast and a Coastal Flood Watch has been
issued for late Sunday night through Tuesday morning.

&&

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

A trough will deepen over the Bering through Saturday resulting
in a strengthening surface low pressure system tracking west to
east across the Aleutians. Strong cold air advection on the
backside of the trough will lead to gusty winds late Saturday into
Sunday for the south side of the Alaska Peninsula. Winds
sustained to around storm force is possible with locally higher
gusts through wind prone areas. A trailing ridge will bring a
brief reprieve before a much stronger low enters the western
Bering and strengthens through Monday. Gales may begin for the
Western Aleutians after midnight Saturday into Sunday. Winds on
the southern edge of the storm in the southern Bering, touching
the Aleutian islands, will increase to storm force by Sunday
evening. High end storm force winds appear to track across the
southern Bering through to Bristol Bay through Monday. Winds may
peak near the Pribilofs late Monday morning into the afternoon.

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

Expect a parade of lows this forecast period. The latest run of
the GFS/ECMWF/Canadian are reasonably clustered on Tuesday and
consistent with the ensembles. Tuesday cold temperatures will
persist across Southcentral and the snow level is decreasing.
Recent runs of the global models suggest a more southerly track
for the first low to impact Western Alaska veering it towards
Bristol Bay. The models continue to have a highly amplified
pattern. By Wednesday, divergence in solutions has emerged over
the Bering but the Gulf Of Alaska is still in good agreement with
the low there and bringing a tropical fetch towards Southcentral.
By midweek next week there is a high probability of additional
pattern amplification as an upper low dropping southeast out of
NE Russia and moves across the Aleutians. Late this forecast
period another low will move from China into the Northwest Pacific
and towards Attu.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Coastal Flood Watch 155 161.
MARINE...Storm Warning 130 132 150.
         Gale Warning 119 120 1 31 137 138 155 160 165 170 171 172 173
         174 177 178 180 351 352
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...ED
SOUTHCENTRAL ALASKA...CL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...VR
LONG TERM...PS