Gale Warning 602, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
817 PM AKDT Sat Oct 8 2022

.ANALYSIS AND UPPER LEVELS...

A broad upper level trough is situated along an axis that extends
over the west coast of Alaska from Norton Sound to Bristol Bay.
This trough has continued to "dig" farther south as it tracks from
west to east. Farther east, an upper level ridge is in place over
the Alaska panhandle. At the surface, a strengthening low
associated with the upper level trough is centered near the
Alaska Peninsula over Bristol Bay. Strong pressure gradients have
allowed gusty south to southeasterly winds to persist across
Southcentral, including Portage Valley, Turnagain Arm, Anchorage
Hillside, and Knik River Valley. Due to downsloping, many
locations in the Anchorage Bowl have remained dry however across
the Inlet to the west, moderate to heavy rain remains in place as
southerly flow advects moisture northward over the southern
Susitna Valley. Additionally, moderate to heavy rain is filling in
over the Alaska Peninsula both along the Bristol Bay coast as
well as over interior locations. Gusty southerly winds and rain
persist along the northern Gulf coast including Prince William
Sound as the digging upper level trough works to strengthen the
pressure gradient and advect moisture northward.

&&

.MODEL DISCUSSION...

Model solutions remain in mostly good agreement for the short term
forecast. Run to run consistency has confirmed a more southerly
track for both the low in the Gulf as well as the incoming Bering
low. Forecast challenges remain regarding the arrival of a colder
airmass over Southcentral Tuesday. Currently the NAM solution
brings a surge of cold air at 850 mb while the GFS is more
conservative. This difference, combined with the timing of
precipitation, will drive the potential snowfall amounts
Southcentral sees late Monday into early Tuesday. Confidence in
amounts remains low as there are several finer details that need
to be worked out. Finally, regarding the Bering low, there is good
agreement on the location and track of the low as it moves
eastward Sunday night, however the 18Z NAM run is coming in a
little bit faster than the EC/Canadian solution. Models
consistently show impressive cold air advection on the backside
of this Bering low, which introduces the possibility for gusty NW
winds along the central and eastern Aleutians on Monday.

&&

.AVIATION...
PANC...VFR conditions are expected to persist. Conditions may drop
to MVFR in passing rain showers. Gusty southeasterly Turnagain
Arm winds will taper briefly during the afternoon hours today.
Another surge of gusty winds is expected between 4Z-6Z before all
winds eventually diminish by the early morning hours Sunday.

&&

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

A general rainy pattern persists for much of Southcentral with
intermittent precipitation in the Anchorage Bowl due to downsloping
with a cross- barrier flow. The flow will shift gradually tonight
and bring some light precipitation into the Anchorage Bowl
overnight into Sunday. The low pressure system providing this
precipitation pattern will move East out of the area starting
Sunday afternoon, bringing the precipitation out with it. The next
system to enter the region will be a low approaching Kodiak, from
the Alaska Peninsula Monday morning. This low will push into
Southcentral Monday afternoon with some lingering precipitation
overnight.

The feature on the forefront of our minds today is the gusty
conditions found all across Southcentral today. Gusty conditions
higher than expected began this morning in places such as
Turnagain Arm, Anchorage Hillside, Whittier, and Gulkana, are
persisting, and will continue into tonight. A High Wind Warning
was issued for the Anchorage Hillside with observed gusts higher
than 65 kts this afternoon. A lull is expected late this afternoon followed
by a resurgence in the evening. Winds currently expected to remain
gusty in the Copper River Basin for much of the weekend, with
gusts picking up Monday afternoon.

Potential snowfall has been a focus for the next few days. As far
as tonight and tomorrow are concerned, the chance of snow across
Southcentral has been lowered significantly. Temperatures
associated with our current low pressure system are well above
freezing at the 850 mb level, dashing much of the snow concern
tonight. Tomorrow the temperatures will be lower, but the
precipitation will be out of the area. Monday will see lower
temperatures, as well as the next low pressure system, kicking off
some precipitation Monday. This set up seems to provide the most
potential Monday night, with snow accumulation currently possible
in the Anchorage hillside, the northern Susitna Valley and along
the northern Richardson highway near Paxton.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 2)...

A trough of low pressure continues to dig across Southwest this
evening with scattered showers and widespread cloud cover. This
activity is expected to shift eastward and out of the region later
tonight as the trough and its associated surface low push into
the Gulf of Alaska. Gradual clearing from west to east is
forecast; however, the resulting pressure gradient from the
departing low will promote gusty northwesterly winds over much of
Southwest through the morning hours on Sunday. The windiest
conditions are anticipated over interior Bristol Bay where gusts
to over 40 mph will be possible. A colder air mass will move into
Southwest through the overnight hours and Sunday morning low
temperatures across Southwest are expected to dip down into the
lower 30's. Normally this would promote a concern for snow, but it
looks like most of the precipitation will have moved out of the
area before freezing temperatures occur. Thus, any snow at all
will be relegated largely to the higher elevations.

By Sunday night, shortwave ridging is forecast to move across
Southwest in advance of the next approaching frontal system, which
may allow Monday morning lows to drop down into the low to mid
20's. A front will reach the coasts of the Kuskokwim Delta and
Bristol Bay during the late morning hours on Monday with
increasing temperatures and showers. Enhanced westerly winds are
expected to contribute to enhanced surf along the Alaska Peninsula
from Egegik, southward. A high surf advisory has replaced the
previous Coastal Flood Watch as the track of the low has trended
further south. It is in effect from Monday morning into Monday
afternoon.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 2)...

A trough of low pressure is pushing across the Alaska Peninsula
and into the Gulf this evening. Small craft northwesterly winds
and some embedded gales are occurring from Nunivak Island into the
Eastern Aleutians. The threat for gales will persist into the
overnight hours, especially along the Bristol Bay Coast down into
the lower Alaska Peninsula. Gales with storm force gusts will be
common through the gaps and passes of the AKPEN from King Cove,
eastward to Kodiak Island. Further west, from the Pribilofs into
the western Bering, calmer conditions are noted. Though this will
be short- lived as the next upper low and front push into the
Western Aleutians tonight. Low pressure is forecast to track along
and just north of the Aleutians with gale force winds and higher
gusts through Sunday afternoon. Strong cold air advection on the
backside of the low will allow for storm force winds gusting to to
as high as 65 knots from Dutch Harbor to Cold Bay by Monday. 20
foot seas previously confined to the Pacific side of the Aleutians
through Sunday, should expand to the Bering Side Monday morning
as the center of the low tracks east of the Pribilofs and
eventually into Bristol Bay by Monday afternoon. High wind
warnings are in effect for the Central and Eastern Aleutians on
Monday.

&&
.LONG TERM FORECAST (Days 4 through 7: Wednesday through
Saturday)...

Cold air is going to move across Southcentral. Expect multiple
lows this forecast period. The latest run of the
GFS/ECMWF/Canadian are reasonably clustered Wednesday through
Friday. The major trend suggests that there will be abrupt change
from above normal temperatures to wintery conditions for
Anchorage. There is a closed low settling over the high latitudes
of the Arctic Ocean that will favor the rotation of a series of
progressive troughs underneath into the Brooks Range. The models
continue to have a highly amplified pattern with the longwave
trough over the Bering.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning 101, High Wind Watch 181 185, High Surf
         Advisory 161.
MARINE...Storm Warning 130 131 170.
         Gale Warning 119 120 125 132 138 139 141 150 155 160 165
         171-180 351 352 411-414.
FIRE WEATHER...NONE.

&&

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

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