Gale Warning 676, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
542 AM AKST Sat Dec 14 2019

.ANALYSIS AND UPPER LEVELS...

A closed blocking high continues to dominate the northern part of
Alaska. A once strong gale force North Pacific low now over the
southern Kenai is beginning to finally move inland as the upper
closed low opens up into a shortwave trough. Over the Pacific
Ocean,a strong storm force low along the eastern periphery of a
larger upper trough is moving north into the Eastern Aleutians.
This low is rather compact in nature as evidenced by satellite
imagery and ASCAT wind passes from the polar orbiters, with the
strongest core of cold air advection storm force winds still over
the open waters of the Pacific. Over the mainland, extensive fog
and stratus has formed over Southwest Alaska behind a departing
and weakening sheared out upper shortwave trough. Rain showers are
still pushing up along the North Gulf Coast, and some inland
sprinkles are pushing over the Chugach into Anchorage and the
western Kenai. Temps continue to run well above normal for inland
Southcentral (except the Copper Basin).

&&

.MODEL DISCUSSION...
Same story as yesterday as the models are in excellent agreement
with the large scale pattern heading out into next week now, but
are in lesser agreement with the strong storm moving over the
Eastern Aleutians today and tonight, and a series of frontal waves
which will move up toward the Alaska Peninsula and into Bristol
Bay Sunday. For now, a continued blend to the GFS was favored as
it fits a good middle ground with everything, and shifts the
strong eastern Aleutian low farther east which now puts the center
over Dutch harbor, with the strongest winds all around Dutch.

&&

.AVIATION...
PANC...There still remains a chance of light precipitation as the
upper low over the Gulf opens into a trough and crosses overhead
of Anchorage between about 12Z and 18Z today. However, low level
southeasterly flow will persist, so VFR ceilings should persist.
Precipitation-type is also a challenge, with forecast soundings
maintaining at least a small above freezing layer. Could see rain,
freezing rain, or even snow - but precipitation will be very
light and possibly not even measurable. As the upper wave passes
by, Turnagain winds will bend into Anchorage, which will cause
temperatures to jump to well above freezing. These winds will be
relatively short-lived. As a front moves into the southwestern
Gulf Saturday afternoon, down Inlet pressure gradients will
strengthen and push the Turnagain wind back over the northern
Inlet.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Sat and
Sun)...
A vertically stacked low will eject over Southcentral early today
while a new front will push into the Western and Northern Gulf of
AK by tonight. The radar is showing widespread returns this
morning from the Southern Susitna Valley down through Middleton
Island. This is a result of the low moving from due south to north
over the Kenai Peninsula and Cook Inlet. Even though the radars
are active, precipitation is having a hard time making it to the
ground for most places thanks to dry air in the low levels of the
atmosphere. As moisture increases this morning, we still expect a
likely chance of some wintry mix to fall around the Cook Inlet, to
include possibly some freezing rain in the colder spots (East
Anchorage). However, anything that does fall should be very light.
For higher elevations such as Turnagain, Thompson, and Hatcher
Passes, a couple inches of snow will be possible through the
morning. Gusty southeast winds will also accompany this low
through many of the usual gaps and higher terrain. Some of these
winds could briefly mix into West Anchorage later today, though
gusts should only be to about 25 mph at most.

A new front will start to work into the Western Gulf by tonight.
This will cause the winds to switch around again for places near
the Cook Inlet thanks to an offshore gradient. This means that the
Matanuska Valley will remain breezy heading into Sun. Rainfall for
the coastal areas will slowly wane late Sat and through much of
Sun for the first time in several days. The exception to this will
be Kodiak Island where the front will bring rain back in earnest
by Sat afternoon. Then, by Sun afternoon, the front will start to
track up along the southern Kenai Peninsula and bring steady rain
back into Western Prince William Sound. Most inland locations will
remain dry on Sun thanks to cross-barrier flow at mountain top.
This flow will also continue to keep temperatures quiet mild for
mid-December.

&&

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

A low centered over the eastern Aleutians continues to slowly lift
northward. Its front will spread in over Southwest today, bringing
gusty southeasterly flow. The Kuskokwim Valley will not see much
precipitation from this front today as the occluded system pulls
the boundary northwestward across the Bering.

A second front moves into Southwest Sunday morning, bringing
another round of gusty southeasterly winds. Current thinking is
that most of the precipitation will be around the Bristol Bay
area, though the Kuskokwim Delta coast may see trace amounts of
snow Sunday. Winds will generally weaken by Sunday evening, as the
low in the eastern Bering moves into the Gulf of Alaska for the
start of the workweek.

&&

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

Active weather continues for Bering this weekend. First, a strong
low centered over the central Aleutians has brought gales to much
of the southern Bering Sea with an area of storm force winds over
the water on the south side of the low center. As this storm
slowly lifts toward the northeast, storm force winds are possible
on the western side of the low by this evening, mainly between
Atka and Nikolski. As this low weakens and exits to the south,
another low approaches the western Bering by Sunday afternoon.
The associated front will bring gale force winds to the western
Aleutians. Warmer, southerly flow will allow for precipitation to
fall as rain on the east side of this storm, while mixed
rain/snow or all snow will fall on the west side of the low
as colder air is drawn down from the north.

&&

.MARINE (Days 3 through 5/Monday through Wednesday)...
The storm track during this period will be from the Aleutian
Islands eastward to the Gulf of Alaska. High end small craft
advisories or gale warnings will be the norm as each storm system
moves through. Forecast confidence with low and frontal positions
is above average.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The global models are in decent agreement with the synoptic
pattern for north Pacific and Bering through Thursday December
19th. At the onset of this forecast period there are two lows, one
near the AKPEN and a Kamchatka low. There is a dome of high
pressure between the two. There are some minor difference with the
timing of two different cyclones but the forecast intensity is
only a few millibars off, and the forecast track is very similar.
Expect these systems to move from west to east with the first
storm tracking into the Gulf Of Alaska. All the while, the second
storm will head into the Bering with the frontal boundary pushing
across the Aleutian chain. For Southcentral Alaska, temperatures
will be near or slightly above normal. For the Anchorage metro
area the chances of snow in this forecast period look very slim
given the current run of the models.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 155 172-174 130 131.
		 Gale Warning 413 414 150 160 165 170 175-180 351 352 119 120 132-139 141.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...SB/PJS