Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 230137
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
437 PM AKST Sun Jan 22 2017

.ANALYSIS AND UPPER LEVELS...
There is a large upper low centered over the central Aleutians.
The leading front is pushing into the Alaska Peninsula, bending
back westwards across the southern and central Bering Sea. High
winds and even some Blizzard conditions area associated with this
system. There is a weak short-wave ridge over southwest Alaska
where very cold temperatures persist. A negatively tilted upper
level trough is pushing northeast across south central Alaska,
with some associated snow showers.

&&

.MODEL DISCUSSION...
The numerical models are in good agreement today. There are some
differences in how they handle the precipitation amounts and
types. Thus the forecast confidence is just a bit above normal.

&&

.AVIATION...
PANC...MVFR conditions in snow showers are likely into the early
evening, then transitioning to mostly VFR.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Light snow showers will taper off by early evening over the
Anchorage area and western Prince William Sound. Any lingering
showers will begin to shift eastward this evening, as the upper
level trough providing support tracks inland over the Northern
Gulf Coast. However, due to less available moisture and weakening
upper level forcing, showers should remain light as they track
through central and eastern Prince William Sound tonight.

By Monday a strong front will push into the Gulf of Alaska
supporting another round of precipitation and gusty winds.
Recent models have trended stronger along the northern Gulf Coast,
with storm force gusts expected along the coast. The most
uncertain aspect of this system is the amount of warm air it will
pull northward. If enough cold air remains in place, moderate to
heavy snow would occur again across the eastern Kenai Peninsula
Monday night into Tuesday. However, it is also possible that
enough warm air will be present to limit snowfall totals and
result in heavy wet snow. The current forecast is leaning toward
the bulk of precipitation being snow from the onset of the system
through later Monday night, then transitioning to rain Tuesday
morning. On the other hand, most areas west of the Chugach and
Kenai mountains are expected to see snow Monday night through
Tuesday morning.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Frigid temperatures will persist for one more night across the
southwest mainland before beginning to moderate with the arrival
of the strong Bering front along the coast on Monday. Increasing
winds in advance of the front will produce very low wind chill
values over the Kuskokwim Delta through early Monday morning. The
front will then bring blowing snow to western portions of Bristol
Bay during the morning, with the worst conditions expected to last
into late Monday night before snow begins to diminish. Blowing snow
will also be possible along the delta, but visibilities are
expected to remain above advisory criteria as snow amounts and
intensity will be lower than in Bristol Bay.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The powerful North Pacific low and associated front will continue
to impact the southern Bering Sea with strong winds and heavy
precipitation through Monday as the front continues to push
eastward towards the southwest coastline. Hurricane force winds
will continue over the waters of the southwest Bering through
tonight in cold advection on the backside of the low, with
blizzard conditions continuing to impact Shemya through around
midnight. Meanwhile, conditions will improve through the evening
hours across the Eastern Aleutians as the front moves to the east
and warmer air changes lingering precipitation to rain. The Winter
Weather Advisory has been upgraded to a Blizzard Warning for the
Alaska Peninsula with the issuance of the afternoon package as
visibilities have deteriorated to 1/4 mile near Cold Bay.
Conditions will then improve from west to east during the late
evening with the eastward advance of the front. Blizzard
conditions will be most persistent over the Pribilof Islands as
colder air remains in place to the north of the front, with
conditions finally beginning to improve by Monday afternoon as
snow diminishes in intensity.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The longwave trough continues to remain over the Bering Sea and extending
southward into the North Pacific Ocean through midweek. This
synoptic feature moves eastward, becomes negatively tilted before
moving into the Gulf by Friday. This coincides with the strong
southeast to northwest jet streak tracking into the Southeast
Panhandle by Wednesday. This pattern remains intact through next
weekend. Southcentral Alaska, and the Gulf will have a warming
trend heading with temperatures to rise above freezing by the
midweek time-frame through the weekend. This results in abundant
moisture streaming into the Southcentral region resulting in a
wintry mix along the coastal communities. While the interior sets
up with a better scenario for moderate snowfall in favored
mountain regions. Meanwhile, the majority of the Bering Sea
temperatures remains cold with the northerly flow through Friday
before a warming trend begins from the Western Aleutian/Bering by
Saturday spreading eastward. This coincides with a storm force low
tracking over the Kamchatka Peninsula with associated front
draping through the Western Aleutians. Looking at the models, they
continue to struggling with the complex low in the North Pacific
Ocean as it tracks eastward along the Eastern Aleutians by
Wednesday before moving into the Southwest Alaska region. The next
model issue pertains to a North Pacific low tracking into the Gulf
by Friday. The GFS takes this system over the eastern Gulf, and
the ECMWF tracks this low near Kodiak Island. These storm tracks
will bring warmer temperatures to the Southcentral region.
Therefore, the forecast confidence is below average with these
discrepancies with the storm track.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale 120 125
Storm 119
Heavy Freezing Spray 121

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...TP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...PD



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