Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 020410
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
710 PM AKST Sun Dec 1 2019

.ANALYSIS AND UPPER LEVELS...
A vertically stacked low over eastern Siberia continues to steer
a broad trough northward through mainland Alaska. Temperatures
across the area continue to drop and snow has overspread much of
the Anchorage Bowl and Cook Inlet region. A weak surface low near
Kodiak continues to take shape as it moves towards the Gulf of
Alaska. Temperatures behind this surface feature are considerably
colder, and will be a preview of what`s to come across
southcentral.

&&

.MODEL DISCUSSION...
Model trends continue to be a challenge with snowfall across
southcentral. Synoptically speaking, all guidance appears to be in
lock step with each other. As details are teased out, small
difference exist. As has been the trend over the last few days,
all guidance is showcasing a triple point low within the vicinity
of Prince William Sound. A western track means more snow for the
Anc Bowl, but a more easterly track can significantly pull those
values down. Guidance this morning is keeping the trend with more
of an easterly track, near Cordova. That said, guidance is still
keeping the lighter snowfall continuing across much of the region
through Monday. See the Southcentral discussion below for further
information.

&&

.AVIATION...
PANC...Light snow showers will become steady tonight as a Gulf
low approaches Prince William Sound. By late tonight, expect
steady snow at the terminal to bring vsby down to LIFR.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

A strong triple point low has formed over the Gulf of Alaska and
is currently heading toward the northern Gulf coast and Prince
William Sound. As the associated front nears, strong easterly
gales and rain are expected across the northern Gulf. On the
backside of the low, strong outflow winds over Kamishak Bay and
the Barren Islands may reach storm force levels beginning tonight
and lasting through Monday as strong cold air advection occurs
and a large amount of cold air on the west side of the Alaska
Range begins to spill eastward.

As the low center nears Prince William Sound, snowfall is expected
to pick up in intensity over the Cook Inlet area beginning
tonight, and will peak in intensity during the early morning hours
on Monday. Winter Weather Advisories have been issued for the
western Kenai Peninsula, Anchorage, the Matanuska Valley, and the
Copper River Basin. For the Copper River Basin, expect snowfall
to be heaviest south and west of Gulkana. As the low center
eventually moves south by Tuesday, temperatures are expected to
plummet by midweek, with lows across much of Southcentral in the
single digits by Tuesday night.

&&

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

Upper level ridging will continue to build in over much of
Southwest Alaska this afternoon through tomorrow afternoon. This
will lead to clearing conditions in terms of precipitation and
cloud cover moving into the first half of the week, with the
exception of the coastal areas, which could see a chance of snow
showers for Monday afternoon.  Northerly flow over the Southwest
will bring in cold air advection for the region. This will result
in favorable conditions for blowing snow near Iliamna, which
received the heaviest amounts of snow from the last storm.

Temperatures across Southwest Alaska will be on a downward trend
throughout the week as the cold air continues to move into the
region. High temperatures today will be in the 20s for most
areas, but will drop into the teens for the Kuskokwim Delta and
interior Bristol Bay, with highs in the single digits for the
Kuskokwim Valley, by Tuesday afternoon. Low temperatures will drop
near or below zero degrees by Tuesday night heading into
Wednesday morning, with coastal areas expected to stay a bit
warmer.

&&

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

Gale force winds south of the eastern Aleutians and Alaska
Peninsula will continue to exit into the Gulf through the night.
Small craft will spread across the Bering through tomorrow morning
associated with a low in the northern Bering. These winds will
increase to gale force tomorrow afternoon stretching across the
central Bering as the trough axis extends and merges with a North
Pacific mesolow south of the central Aleutians. The next big gale
force system moves across the western Chain on Tuesday morning and
will continue its track southeastward throughout the day.

&&

.MARINE (Days 3-5)...

The forecast period commences with weak cyclonic flow over the
Gulf Of Alaska, a ridge axis over the central Aleutians and a
Kamchatka low impacting the western Bering. This pattern will push
eastward Wednesday and Thursday. The primary marine hazard area
will be gales over the western Bering. There is also the potential
for heavy freezing spray near Nunivak Island and over the northern
Bering.

&&

.LONG TERM FORECAST (Days 3-7)...

The models are struggling in the long term forecast period but
there are a couple of consensus items with the global models. The
longwave pattern will feature troughing over the Bering and the
ridge axis will move into southwest Alaska and southcentral
Alaska. There are multiple shortwaves embedded in the upper
trough. Its a very dynamic and unsettled pattern for the Bering.
However, with the high amplitude ridge in place over much of the
mainland a more stable and southcentral should get a break from
the precipitation for a few days.


&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 101 111 121 141 161.
MARINE...Gale 119 120 132 137 138 150 173-177.
 Storm 130 131
FIRE WEATHER...NONE.

&&
$$

SYNOPSIS AND MODEL DISCUSSION...SS
SOUTHCENTRAL ALASKA...KO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AH
MARINE/LONG TERM...PJS


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