Small Craft Advisory 224, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
355 PM AKDT Tue Mar 14 2017

.ANALYSIS AND UPPER LEVELS...
A dominant upper level high pressure center over the Bering Sea
remains in control of the weather across the Alaskan domain. Calm
weather continues across the Bering Sea, with cold and gusty
northerly flow across all of mainland Alaska. The outflow wind
pattern remains the most pronounced along the coastal areas, with
Seward, Whittier, and Valdez experiencing the strongest winds. A
shortwave dropping down over southcentral this afternoon is
working in concert with the strengthening sunshine this time of
year to help mix gusty winds down to the surface in many interior
areas as well. These should begin to wane somewhat by this
evening before the next shortwave moves into the area toward
morning.

&&

.MODEL DISCUSSION...
As one would expect by an unchanging longwave pattern, the models
are all in excellent large-scale agreement. There are some
struggles with the extent and intensity of cold-advection
instability snow showers over the eastern half of the Bering Sea,
and the exact positioning of individual surface low centers in the
Gulf of AK. Hi-resolution models were used when available,
combined with a healthy portion of forecaster experience to add
value where the models are struggling to pinpoint local details.

&&

.AVIATION...
PANC...Cold and clear VFR conditions will continue throughout the
forecast period. Gusty north winds will continue through late this
evening before losing the gustiness overnight but still
maintaining a 10 to 15 mph north wind through Wednesday morning.
Gusts will redevelop again Wednesday afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Offshore flow continues to dominate the regional pattern today as
cold air from the arctic pours into Southcentral behind a dynamic
shortwave trough. Diurnal mixing is also helping to enhance winds
and gusts across the region. Rather cold air aloft will move in
tonight, but only valleys and low lying areas away from the
stronger winds will realize cold morning lows. Cold air advection
wanes through Thursday, so the pressure gradient along the coast
will also relax. Offshore winds will continue but will weaken in
response.

The closed low in the Gulf of Alaska will retrograde west and
bring mid level clouds to most of Southcentral by tomorrow with
increasing threats for light snow in the Eastern Copper Basin
into Prince William Sound Wednesday into Thursday. However, dry
air in place and continued northerly winds will limit coverage or
intensity of inland snow showers. The remainder of Southcentral
will remain dry.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A very persistent pattern will provide little change to the
current weather looking through the middle of this week. Gusty
northerly winds are expected to continue under otherwise sunny
skies with cool temperatures as cold air advection from the
interior continues. This will keep daytime high's slightly below
normal. During the overnight hours, continuing winds will prevent
inversions from developing, keeping overnight lows near to above
normal. Winds will then diminish on Friday as high pressure moves
in from the Bering Sea, allowing for lighter winds, sunny skies
and near normal temperatures.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
High pressure remains in control of the Bering Sea. A weak
boundary on the north/east side of the high will keep chances for
snow across the central Bering. Otherwise, the main story is gusty
winds through the Alaska Peninsula, where storm-force gusts
through bays and passes can be expected into Friday. Over the
Western Bering the pattern will begin to change late Wednesday as
a gale force front moves into the area. This front will bring
gale force winds and rain to the Western Aleutians for Thursday
and Friday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
A front will affect the western and central Aleutians through the
weekend with small craft and gale force winds. This front will
also be associated with periods of rain and snow. By early next
week high pressure will build south across the Bering with a
drying trend for most of the Bering and Aleutians.

Southwest AK will be cool and dry through Tue, except for a few
snow showers affecting the Kuskokwim Delta beginning on Fri.
Gusty northerly winds through the Aleutian Range will diminish on
Fri.

Low pressure rotating around the Gulf of AK, combined with high
pressure over the mainland, will bring periods of windy
conditions to channeled terrain of southcentral AK through Fri.
Impulses moving around the Gulf low will then bring some snow to
the north Gulf coast on Sat that has a chance of moving inland on
Sun. Although models are starting to indicate this inland snow,
confidence remains fairly low. The trajectory of the low moving
through the gulf, and associated impulses producing precipitation,
are difficult to pinpoint and will be watched closely during the
next few days.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning 119>121 127 128 130>132 136>140 150.
         Heavy Frz Spray 121 138 139 141 150 165.

&&

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...JA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...DS