FXAK68 PAFC 161347
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
447 AM AKST Tue Jan 16 2018
.ANALYSIS AND UPPER LEVELS...
A large 971 mb low is located in the southern Gulf of Alaska this
morning with an associated front pushing westward toward the
Kenai Peninsula. Gale force winds behind this front are also
helping spread yet another surge of unseasonably warm air toward
Southcentral Alaska, with rain already falling along the coast and
freezing levels upwards of 2000 ft in the coastal mountains.
Meanwhile, partly cloudy skies across Cook Inlet last evening
allowed temperatures at the surface to drop into the mid to upper
20s in most locations, which has set the stage for some freezing
rain this morning along the western Kenai Peninsula and Anchorage
Bowl areas this morning. Southwest Alaska is currently partly
cloudy with winds diminishing and some areas of low clouds/fog
forming, but this will be short-lived as clouds and eventually
precipitation from the low in the Gulf will be spreading quickly
into the area this morning.
Further west, nearly the entire Bering Sea/Aleutian region is
under relatively tranquil conditions, with cold air continuing to
slowly spill off the Siberian landmass. This cold air over the
relatively warm ocean waters is producing widespread snow showery
activity across the Bering Sea and North Pacific.
The models are in good overall agreement for the next few days,
especially to the east of the Alaska Range. The largest model
discrepancy revolves around the position of a storm and associated
front that will move into the western Bering/Aleutians this
evening. The NAM is much faster than any of the global models in
progressing this storm across the Bering Sea, and as a result was
not considered in the overnight forecast blend (it is not
terribly surprising to see this considering the storm is
currently outside of the NAM forecast domain).
PANC...Low VFR conditions and occasional MVFR ceilings will
continue this morning as weather moves into the area from the
east. Freezing rain will remain a possibility throughout the
morning before mountaintop winds kick in strong enough to result
in stronger downslope/drying conditions (and higher VFR
conditions) by this afternoon.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The low tracking through the Gulf from the southeast is pushing
the warm sector of the system over the north Gulf coast and
southcentral Alaska today through tomorrow. The northerly surface
winds down Cook Inlet have helped keep temperatures below freezing
with temperatures aloft above freezing from around 750 ft to 4000
ft on this morning's Anchorage sounding. Freezing rain has fallen
over the Kenai Peninsula and Turnagain Arm. Anchorage has
benefited from a distinct dry layer around 1500 to 2500 ft but
that layer looks to be dissipating as the heavier precipitation
moves in. Therefore even though freezing rain has not developed in
the Anchorage area as of this writing, it still looks to be on
its way for the rush hour commute. Farther north toward the
Matanuska Valley, the freezing rain looks less likely to have
widespread impacts as any that falls should be very light. By this
afternoon temperatures will increase to well above freezing for
the Cook Inlet region making precipitation for the aforementioned
areas all rain.
The Copper River Basin is also at risk for some light freezing
rain today. By tonight temperatures aloft should have cooled
enough to make precipitation all snow there.
.SHORT TERM FORECAST SOUTHWEST ALASKA...
The front moving through Southcentral Alaska will make it to
southwest Alaska later this morning and then spread west across
the rest of southwest Alaska by this evening. The majority of the
precip should fall as snow but there is a chance for areas north
of King Salmon to see light freezing rain mix in this afternoon
with the push of warm air moving in aloft. Snow will then linger
but diminish on Wednesday before clearing out of most locations on
.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
Northwest flow will continue over much of the Bering and Aleutians
today bringing light precip to these areas. To the west, weak
ridging is moving in ahead of a North Pacific system that is
approaching the western Aleutians. The front associated with this
system looks to make it to the western Aleutians Tuesday afternoon
and be warm enough to have some rain mix in with the snow. The
front will then track east making it to the eastern Aleutians
Wednesday night before stalling and diminishing.
.LONG TERM FORECAST (Days 3 through 7)...
No major changes to the long range forecast today as the trend for
quieter and colder weather still looks to be on track. Beginning
Thursday, weak ridging will develop over the eastern half of the
state bookended by a deep low over the SE coast and a rapidly
weakening surface low over the SW mainland. The jet stream will
migrate south keeping the storm track positioned away from
mainland Alaska. An upper level ridge will amplify over the
Bering and move east through the weekend which will lead to
northerly offshore flow over the western half of the state. This
will draw bitterly cold air down from the arctic and steadily
decrease temperatures across most of the area, with the coldest
plunge of arctic air seen over western AK where temperatures could
drop well below average by Sunday.
Further west, models are locking in on the next storm system
moving into the Western Bering on Saturday. A front looks to move
east across the western and central Aleutians over the weekend but
will stall and wash out as persistent high pressure to the east
blocks any further progression. Beyond this weekend, models
become disorganized and out of agreement, but generally show the
storm track staying to our south as ridging holds on over the
mainland keeping us in a colder/drier pattern.
PUBLIC...Winter Weather Advisory 101 121
MARINE...Heavy Freezing Spray 181 185
Gale 120 125 130 131 132 138 139 140 150 155 178 180
SYNOPSIS AND MODEL DISCUSSION...AMD
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DWK