Small Craft Advisory 973, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
451 AM AKST Tue Dec 17 2019

.ANALYSIS AND UPPER LEVELS...

A disorganized area of low presure exists south of the Aleutian
Island chain and is drifting southeast. This low is continuing to
produce rain showers and low level cloud cover. Behind this low,
the push of cold air can be seen beginning to develop on satellite
with flow switching to a northerly direction and moving cloud
cover southward.

In southcentral AK, the decaying stationary front continues to
produce showers along the Gulf coast, with calm weather over
inland areas. The next front set to impact the southcentral coast
can be observed on satellite moving north through the Gulf of
Alaska. This front is an extension of the disorganized area of low
pressure that is south of the Aleutian Islands.

&&

.MODEL DISCUSSION...

Models continue to be in good agreement for the short-term both
between each model and each model run. Therefore, there is high
confidence in the forecast with just minor adjustments to the
new forecast package.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The remnants of the weather front along the north Gulf coast are
bringing in rain and snow showers to the coastal areas with a few
snow showers making it over the coastal mountains. Inland areas
will continue to remain dry. Some colder air is filtering into the
region which will see more of the precipitation tilt toward the
snow showers from rain showers.

Another front will make it to the north Gulf coast Wednesday
morning, but this front will rapidly weaken as well. After this
front dissipates, there will be generally high pressure over the
mainland part of the state with broad low pressure in the Gulf of
Alaska. This will potentially bring in some gusty northerly winds
through channeled terrain along the north Gulf coast Wednesday
night and beyond.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Today and
Wednesday)...

Southwest Alaska will be between two large-scale weather systems
through Wednesday. A nearly stationary area of Arctic high
pressure over northern Alaska will persist through Wednesday.
Meanwhile, an area of low pressure will move east along the
Pacific side of the Alaska Peninsula today and push into the Gulf
on Wednesday. In this pattern, cold and dry weather will be the
rule. The last remnants of a dying front over Southwest Alaska
will keep the area fairly cloudy starting out the day, but the
skies should be clearing through the day today. In addition, the
winds will be out of the northeast, staying offshore. This will
support moving increasingly cold and dry air into the area from
the interior. Thus, as mentioned yesterday, temperatures will drop
towards normal December levels today and tomorrow, followed by
below average temperatures late week into the weekend. The dry
weather will allow for plentiful weak December sunshine for the
foreseeable future as well.

With that said, as temperatures drop late week, the winds will
remain fairly steady. This could lead to wind chills dropping
below 30 below at times, with the start of this threat beginning
Wednesday night. So far we do not expect there to be many areas
where both wind chills below 40 below and wind speeds of 15 mph
sustained will be concurrent. Near Bethel and out towards the
Delta, the wind speed criterion will be there, but it is not
expected to be quite cold enough. Meanwhile further into the
interior, Aniak's wind chills could approach 40 below, but the
wind speeds will not be there. This will certainly be worth
watching in the coming days as colder air settles in.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2: Today and
Wednesday)...

A weakening front/deformation zone over the western and central
Bering is responsible for the area of strongest winds over the
area this morning. It will sag southward and continue weakening
into tonight. North to northeasterly winds will persist across
much of the Bering through Wednesday. The next strong front will
turn the winds southerly across the far western Bering and western
Aleutians on Wednesday. This front will also produce gale force
winds as it sweeps across the Bering through Thursday. Elsewhere,
the winds and cooler temperatures will persist across the Bering
basin through Wednesday.

&&

.MARINE (Days 3 through 5)...

New guidance is giving higher confidence in the likelihood for
gale force outflow winds in the northwest Gulf around Kodiak
Island Thursday into Friday. A strong North Pacific low is being
suggested by most models for entering the Western Aleutians
Saturday. However, uncertainty exists in the low's track. Guidance
agrees on an eastward path, but deviations in the northward
extent will play a strong role in where the strongest winds are.
Right now, most models agree that gale force winds can be expected
with a couple of outliers suggesting storm force or small craft
level winds.

&&

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

The extended period starts off quiet and cold for southern
mainland Alaska, as an upper level low allows for more winter like
temperatures to return through the weekend. A more active period
will ensue Saturday with a storm system that will bring more
active weather to the Aleutians and progress into mainland Alaska
to start the work week. Warm Pacific air will likely intrude on
the colder air in place and precipitation can be expected for
Bristol Bay and much of southcentral Alaska on Monday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES: 119 120 130 131 175-178
FIRE WEATHER...NONE.

&&
...corrected typo...

SYNOPSIS AND MODEL DISCUSSION...BJB
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW
MARINE/LONG TERM...LTB