Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 171824 CCA
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
924 AM AKST Thu Jan 17 2019

.ANALYSIS AND UPPER LEVELS...
A 984 mb surface low is located about 400 miles south of Sand
Point, which is being supported by a 75 kt upper level southerly
jet on the east side of the low. Satellite imagery shows a
secondary surface low developing north of the main low over
Bristol Bay. A front extends over the top of the low complex from
the Kuskokwim Delta coast south across the AKPEN and Kodiak
Island. The upper level southerly jet is pumping in moisture and
warmer air from the North Pacific with radar and local
observations showing rain across Kodiak Island and the eastern
slopes of the northern Aleutian Range, and southern Alaskan
Range. Upper level ridging extends across most of the eastern
mainland, with Southcentral lying in between the low to the
southwest and ridging to the east and north, bringing mostly
cloudy skies but generally dry and quiet weather to the area this
morning.

Further west, an upper level ridge axis is centered over the
central Bering/Aleutians bringing cold northerly flow from the
Pribilofs west. Open cell cumulus can be seen on satellite imagery
streaming south across the central Bering/Aleutians bringing
scattered snow showers to the area. High clouds can be seen
streaming north and east across the western Aleutians out ahead of
the next storm system approaching the area.

&&

.MODEL DISCUSSION...
The numerical models are in good agreement through Friday with
most of the synoptic level features handled well. By Saturday, a
weak complex of surface lows is depicted over the Gulf of Alaska
with models struggling to handle how these lows move and interact
with each other. Overall, with these features remaining well
offshore, impacts to the forecast are expected to be minimal with
the exception of northerly outflow winds along the coast.

&&

.AVIATION...
PANC...VFR conditions and light winds will continue through
Friday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
Remnants of an old front will bring rain to Kodiak Island through
the morning. It will then diminish through the afternoon as the low south
of the Alaska Peninsula pulls the moisture further south. The
pattern will then shift as an upper level low over the Yukon
Territory will pull down cold, dry air over Southcentral Alaska
into the weekend. This will keep the skies clear and allow
temperatures to drop with inland locations dropping into the
single digits. The Copper River Basin will be even colder with
temperatures expected to drop to around negative 20 Friday and
Saturday nights.

&&

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

A frontal band stretching from the Kuskokwim Delta south across
the Alaska Peninsula will begin weakening this afternoon and then
dissipate as it starts to shears apart this evening. A frontal
wave rotating around the north side of a broader vertically
stacked low to the south, will track from east to west across the
Alaska Peninsula tonight. This will strengthen northerly flow and
bring a second round of mixed precipitation (mostly rain along the
south side and snow along the north, with more predominant snow
further to the west) to the Alaska Peninsula. Over mainland
Southwest Alaska, snow along the Kuskokwim Delta coast will taper
off this afternoon with chances for light snow further inland due
to a secondary weak trough extending from north to south tonight.
For Friday and Saturday cool, dry breezy northeasterly flow will
prevail.

&&

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

Upper level ridging over the central Aleutians will build north
across the Bering today and tonight, pushing the arctic trough
north over eastern Russia and the Bering strait. A strengthening
frontal wave will track north towards the western Aleutians today
with the associated surface low lifting just to the west late
tonight. A second stronger low will approach the western Aleutians
from the south Friday and Friday night, spreading a frontal
system across the western and central Aleutians Saturday, and into
the southwest Bering Saturday night. Further to the east, a large
blocking upper level high will build over the north central
Bering on Friday and remain in place through Saturday.

&&

.MARINE (Days 3 through 5...Sat through Mon)...
Confidence has increased in the strength of the easterly winds
over the Western Bering Sat into Sun. This is primarily due to
better agreement on the closed high over the Bering Strait and
some cold air moving in from the Eastern Bering. Thus, have
started to trend winds high bringing them now into the gale force
range. We will monitor this area for the potential for at least
some storm force gusts.

The low that develops late Sun into Mon near the Alaska Peninsula
still has a high amount of uncertainty surrounding it. Most of it
is tied to exactly what happens with the upper level low over the
mainland. So for now, will likely elect to just hold to small
craft winds. The best chance for any gales associated with this
system would be on its southern flank somewhere south of Kodiak
Island late Mon into Tue.

&&

.LONG TERM FORECAST (Days 3 through 7...Sun through Wed)...

The period begins with a dominating upper level Arctic low over
the northern part of the state. As the low deepens and the trough
axis extends over Southwest Alaska, another important feature to
the south comes into view by Mon. A North Pacific low moves into
the southwestern Gulf of Alaska. While all models indicate the
presence of this Arctic low as well as the low in the Gulf,
however model solutions continue to struggle with placement of
the low by Tue. Currently, the EC/Canadian solution places the low
on a track inland through Southcentral thereby introducing warmer
air and moisture, and ultimately warmer temperatures. Conversely,
the GFS places the low track much further east; moving inland
over the Copper River Basin, thereby delaying the warm-up period
over Southcentral for early next week. By the end of the period on
Wed, all model solutions indicate general agreement with the
placement of a North American ridge building over the southern
half of the state. A stretch of warmer weather like this across
South Central is fairly typical in January, so much so that it is
actually reflected in the snow depth climatology for Anchorage. It
is usually accompanied by some downsloping winds.

Meanwhile, over the Bering, a closed upper level high continues
to support cold air advection from Siberia through western AK.
This high slowly drifts westward by Tue and allows an upper level
Kamchatka low over the western Aleutians to advance eastward. By
Wed, this low will ultimately reinforce the building North
American ridge by advecting warmer air in from the south.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale: 155 165 170 172 177 178 411 414.
         Heavy Freezing Spray: 180.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KVP
SOUTHCENTRAL ALASKA...DK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
MARINE/LONG TERM...MO/KO


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