Brisk Wind Advisory 24, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
501 AM AKST Mon Feb 10 2020

.ANALYSIS AND UPPER LEVELS...

On satellite imagery there are two frontal boundaries. There is a
baroclinic zone in the Gulf Of Alaska with a surface low south of
Kodiak and there is an occluded front attached to a 955mb low
southwest of Attu Island. Storm and gale force winds have been
detected with the latter system on ASCAT (advanced scatterometer).
There is a 160+ knot jet core south of Shemya. The blended total
precipitable water parameter which is derived from satellite
imagery (AMSU and SSM/I) has detected a fetch of moisture from
Hawaii to the Gulf Of Alaska and a second and more robust tropical
fetch from the Mariana Islands to Adak and Attu. The Middleton
Island radar (PAIH) has also pinged into the precipitation into
Gulf Of Alaska. All the while, cold air is advancing into the
northern Bering and Southwest Alaska.

&&

.MODEL DISCUSSION...

Models continue to be in synoptic good agreement through the next
36 hours. By 00z Wednesday, some issues emerge in the north
Pacific with the low developing south of the chain somewhere
between south of Dutch Harbor and south of King Cove. The models
all ping into arctic air banked up against the Alaska Range with
some of the polar airmass working its way through the terrain.

&&

.AVIATION...

PANC...VFR conditions are expected this TAF package. Early this
morning the winds were southerly however the expectation is that
"down inlet" flow will develop and northerly wind will materialize
over PANC.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The upper level trough over the area will slowly move east today
and an upper level ridge will build in from the west. The trough
axis will slide into the Copper River basin early this afternoon
and then push into Canada by evening. Some snow showers are
possible to the east of the trough axis, mainly over the Copper
River basin. Strong offshore flow will accompany the arrival of
the ridge, with gusty gap winds rapidly increasing this morning
through the afternoon. These winds will diminish on Tuesday as the
pressure gradient weakens. Another weather system will approach
Kodiak Island on Tuesday. This will bring snow and increasing
winds to the Island during the afternoon. Winds will be quite
gusty, and some blowing snow is possible. Temperatures will warm
to above freezing during the night, and this will limit total snow
accumulations. There is a chance that some rain will mix in later
in the night as well. Some snow with this system will reach the
Kenai peninsula Tuesday evening and increase during the night,
especially on the eastern side.

&&

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

A dry arctic air mass advecting inland from the Bering persists
across the region through Tuesday. A developing front south of the
Alaska Peninsula on Tuesday will bring increasing chances for
snow through Wednesday as the occluding system slowly moves to
the Western Gulf of Alaska. Winds will generally be light until
Tuesday, then become northerly with gusts developing along the
Western Capes.

&&

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

A storm force low southwest of the Western Aleutians moves a
strong front across the western Bering and Central Aleutians
tonight. Gale force southeasterly gusts and rain are expected
along the boundary as moves through today followed by a mix of
rain and snow showers as a colder air mass wraps around this
occluding system. The front weakens as it moves to the Pribilof
Islands and Eastern Aleutians tonight, so precipitation is
expected to be light. Another strong upper level wave rotating
around the parent low will re-enforce precipitation on Tuesday as
it propagates from the Aleutians and north. The Pribilof Islands
will see diminishing conditions during the afternoon with blowing
snow overnight.

&&

.MARINE (Days 3 through 5: Wednesday through Friday)...

A strong low pressure system is expected to move into the Bering
Sea early in the week, but by Wednesday the winds along the front
will be max gale force. Seas will be high with this system,
reaching 30 feet south of the Aleutian Chain on Thursday and
increasing to above 20 feet in the Western Bering Sea.

In the Gulf of Alaska, gale force winds will return on Wednesday
on the north side of a low that is moving across the Southern
Gulf. This will also bring some strong northerly gale force winds
through Shelikof Strait, and southern Cook Inlet. By late
Wednesday winds will increase to storm force along the north Gulf
Coast and south of Kodiak Island as the low progresses eastward.
They will rapidly decrease though, and by Friday, winds will
remain mostly lightly across the Gulf of Alaska.

&&

.LONG TERM FORECAST (Days 3 through 7: Wednesday through
Sunday)...

A strong ~960mb low will approach the western Aleutians from the
North Pacific on Wednesday. Gusty winds and moderate rain/snow are
likely as its associated front tracks across the Aleutians by
Thursday. It will become nearly stationary and weaken Friday into
Saturday as it becomes vertically stacked with an upper low near
Atka. While this will lead to gradually diminishing winds,
precipitationwill continue through the weekend.

A series of lows will track west to east across the Gulf through
the weekend, bringing precipitation to coastal areas as well as
snow to the Copper River Basin. Exact timing and position of these
are still somewhat uncertain. High pressure will gradually weaken
over the interior, however as a result of the aforementioned
lows, the gradient will remain supportive of northerly winds and
thus temperatures are expected to remain slightly below average
for through end of the week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Heavy freezing spray 121127 129 130 139 141 411 412 414
150 160 165 179 185. Gale 352 351 120 127 129 130 131 411 412 413
414 150 170 172 173 174 175 176 177 178 179 181 185.

&&

SYNOPSIS AND MODEL DISCUSSION...PJS
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
MARINE/LONG TERM...LF/AP