Small Craft Advisory 81, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
452 AM AKST Fri Jan 26 2018

.ANALYSIS AND UPPER LEVELS...
The center of the arctic upper level low followed by the coldest
air aloft is moving from Southwest Alaska, across the Aleutian
Range and over Kodiak Island early this morning. As the trailing
trough swings across the Alaska Peninsula, winds continue to
increase with areas of snow and blowing snow. Over Southwest
Alaska chilly northerly winds have been increasing as well
dropping wind chills in many areas to near minus 40. To the east,
a snow producing frontal system over the northern Gulf and Kenai
Peninsula is dropping slowly to the south in response to the
movement of the upper low. Further west, a high amplitude ridge
stretches from the central Aleutians across the Bering and into
eastern Russia while a frontal associated with a deepening low
tracking towards the Kamchatka Peninsula approaches the western
Bering.

&&

.MODEL DISCUSSION...
Models are in fair agreement through the short term with the
NAM/NAMnest preferred for its handling of the wind details. More
uncertainty is introduced Saturday night and Sunday with regards
to the position of the strengthening low south of the Gulf and the
timing of the associated front as it rotates into the
southeastern Gulf.

&&

.AVIATION...
PANC...VFR conditions will persist today through Saturday with
cold northerly flow keeping conditions dry and fog or low stratus
unlikely.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The upper level low centered over the southwest Gulf of Alaska
will continue to drift south for the next couple of days. This
is bringing easterly flow over the northern Gulf. A surface low
embedded in this easterly flow is currently south of the Kenai
Peninsula and will move over Kodiak Island later this morning and
dissipate this afternoon. Precipitation with this low will
continue to push south and west, with precipitation ending along
the north Gulf coast. Another low over the northeast Gulf will
move quickly across the northern Gulf today and to Kodiak Island
this evening, before dissipating tonight. This low will bring some
scattered showers to the north Gulf coast this evening through
tonight, ending late Saturday morning. Inland areas will remain
dry today through Saturday night as low level offshore flow
continues.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Temperatures will begin to moderate across the southwest mainland
today as the upper low quickly departs to the south and 850 mb
temps rebound to 5 to 10 degrees below zero (C). This "warming"
trend should allow wind chill concerns across the Delta and
Bristol Bay to diminish by this afternoon as temperatures climb
back near or above zero in many locations. Dry offshore flow will
then continue to support cold and breezy conditions across the
region into the weekend as the Bering ridge closes off and drifts
northward, with winds gradually veering from north to northeast
through Saturday. Surface temperatures are expected to remain warm
enough to keep winds chills above advisory criteria from this
afternoon onward.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Numerous convective snow showers will continue to impact the
Alaska Peninsula and Eastern Aleutians today in cold northerly
flow as the upper low drops into the North Pacific. Showers will
then quickly diminish in coverage and intensity tonight as the
low drops south of the area and cold advection shuts off. This
will leave much of the Bering in a benign cloudy pattern through
this weekend as the ridge closes off into a sprawling upper high
over the Chukotka Peninsula. Meanwhile, a front will remain nearly
stationary across the Western Aleutians through Saturday, bringing
rain and gusty southeast winds to Shemya before being pushed back
into the Pacific on Sunday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Models are in good agreement that the blocking high that extends
from the mainland all the way through the central Bering will
continue to hold on through the middle of next week. Beginning
Sunday, a low will move into the Gulf of Alaska, but this is
expected to move off toward the Panhandle while the mainland
remains dry. The main impact from this approaching low will be to
tighten the gradient over the coastal areas; this combined with
the cold air dome settling over the Interior will cause gap winds
to increase Sunday into Monday, bringing cold and windy weather to
eastern Prince William Sound.

By Tuesday afternoon, a low pressure system begins to approach the
Central Aleutians from the Northern Pacific. This is expected to
bring warmer air through the Central Bering through the end of
next week. There is much uncertainty on the placement of this
system and the associated front. Depending on the model solution,
the warm air may progress into the Gulf of Alaska, or it may
remain in the Bering Sea. The differences in the placement of the
low and the front will make the difference between a cold and dry
or a warm and wet forecast, so at this time, confidence in the
long term forecast is low.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind Chill Advisory 155 161.
MARINE...Gale Warning 127 130 150 155 165 170 171 172 178 180.
         Heavy Freezing Spray Warning 121 127 130 137 138 139 140
            141 150 160 165 180 181 185.

&&

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