Gale Warning 596, NWS Anchorage, AK

325 
FZAK62 PAFC 280023
OFFALU

Offshore Waters Forecast
National Weather Service Anchorage AK
323 PM AKST Wed Nov 27 2019

Offshore Waters Forecast for the Bering Sea

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ499-281345-
323 PM AKST Wed Nov 27 2019
.SYNOPSIS FOR CENTRAL BERING SEA...

A 988 mb low over Bristol Bay Wed afternoon will move inland Wed
night. A strong front will move into the western Bering/Aleutians
Thu afternoon. The front will continue into the eastern
Bering/Aleutians into Fri afternoon. 

$$

PKZ411-281345-
Bering Sea Offshore West of 180 and East of the International
Dateline-
323 PM AKST Wed Nov 27 2019

...STORM WARNING THURSDAY...

.TONIGHT...SW wind 20 to 30 kt. Seas 10 to 16 ft.
.THU...S wind 20 to 35 kt increasing to 35 to 50 kt in the
afternoon. Seas 11 to 19 ft. Rain.
.THU NIGHT...S wind 30 to 45 kt becoming SW 25 to 35 kt after
midnight. Seas 16 to 24 ft. Rain.
.FRI...SW wind 30 kt. Seas 19 to 23 ft.
.FRI NIGHT...SW wind 20 to 30 kt. Seas 16 to 21 ft.
.SAT THROUGH MON...W wind 15 to 30 kt. Seas 9 to 17 ft.

$$

PKZ412-281345-
Bering Sea Offshore 171W to 180 and North of 56N-
323 PM AKST Wed Nov 27 2019

...GALE WARNING THURSDAY NIGHT...

.TONIGHT...W wind 30 kt. Seas 14 to 18 ft. Snow showers.
.THU...SW wind 15 to 30 kt. Seas 10 to 17 ft.
.THU NIGHT...S wind 25 to 40 kt. Seas 10 to 18 ft. Rain.
.FRI...SW wind 20 to 35 kt. Seas 13 to 21 ft.
.FRI NIGHT...SW wind 25 kt. Seas 15 to 19 ft.
.SAT THROUGH MON...W wind 10 to 25 kt. Seas 9 to 17 ft.

$$

PKZ413-281345-
Bering Sea Offshore 171W to 180 and South of 56N-
323 PM AKST Wed Nov 27 2019

...GALE WARNING THURSDAY NIGHT...

.TONIGHT...W wind 30 kt. Seas 14 ft.
.THU...SW wind 15 to 30 kt. Seas 10 to 13 ft.
.THU NIGHT...S wind 25 to 40 kt. Seas 11 to 19 ft. Rain.
.FRI...W wind 20 to 35 kt. Seas 14 to 20 ft.
.FRI NIGHT...SW wind 15 to 30 kt. Seas 12 to 18 ft.
.SAT THROUGH MON...W wind 15 to 30 kt. Seas 9 to 16 ft.

$$

PKZ414-281345-
Bering Sea Offshore East of 171W-
323 PM AKST Wed Nov 27 2019

.TONIGHT...NW wind 25 kt. Seas 9 to 13 ft.
.THU...NW wind 20 to 30 kt. Seas 10 to 15 ft.
.THU NIGHT...W wind 10 to 25 kt. Seas 8 to 13 ft.
.FRI...S wind 15 to 30 kt. Seas 9 to 14 ft.
.FRI NIGHT...W wind 10 to 25 kt. Seas 9 to 14 ft.
.SAT...SW wind up to 20 kt. Seas 9 to 13 ft.
.SUN THROUGH MON...W wind 10 to 25 kt. Seas 7 to 12 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
943 PM AKST Tue Nov 26 2019

Updated Long Term and Marine Discussions

.ANALYSIS AND UPPER LEVELS...
A broad upper level trough associated with an upper level low
centered over eastern Siberia stretches south across the western
Bering while upper level ridging in the western Gulf extends north
across Southcentral Alaska. Southwesterly flow in between these
two features is supporting a surface cold front stretching from
central Aleutians to the Kuskokwim Delta and inland to the
northeast. An associated warm front has pushed east across the
Great Bristol Bay area and lower Kuskokwim Valley and is now
spreading across the Alaska Range and into Southcentral Alaska.
The strong onshore southwesterly surface flow pushing into
Southwest Alaska has been changing snow over to rain from west to
east through the day. Over Southcentral Alaska offshore flow is
decreasing but the cold, dry low level air mass in place is
presenting a challenge for precipitation from the overrunning
front to reach the ground.

&&

.MODEL DISCUSSION...
Model differences remain a significant short term forecast
challenge regarding the speed and track of the low developing
south of the Alaska Peninsula as well as how much warm air it will
bring up with it as it tracks north. The 12Z NAM was deemed a
clear outlier with the 12Z GFS, ECMWF and Canadian coming into
somewhat better (though not great) agreement with each other and
the ensemble means compared to the earlier runs. Overall the 12Z ECMWF and
12Z GFS are in the closest agreement and offer a reasonable
consensus solution with the 18Z NAM also coming in similarly.

&&

.AVIATION...
PANC...While the frontal system pushing in from the west will
bring a chance of snow this afternoon and evening, the dry low
level air mass in place will cause most of it to evaporate before
making it to the ground keeping conditions VFR and any snow
accumulations minimal. VFR conditions are expected to prevail
tonight through midday Wednesday with possible wind shear concerns
developing Wednesday afternoon and evening as southeasterly flow
through Turnagain Arm increases. Precipitation will begin
spreading in from the south Wednesday afternoon and evening with
significant uncertainty in both its intensity and how long it will
remain snow.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2/Tonight
through Thursday)...
A major winter storm will affect Southcentral over the next couple
days. Key upper level features include a digging trough over the
north Pacific and an intensifying southerly jet stream out ahead
of the trough which will transport copious amounts of warm and
moist air northward toward the southern mainland of Alaska tonight
through Thursday. At the surface the most important feature is a
cold front progressing eastward from the Bering Sea, with surface
waves tracking northward along it. This will greatly drive the
wind forecast over Southcentral Alaska, with low level pressure
gradient driven gap winds affecting temperatures, precipitation
intensity, and precipitation type.

This is a complex set-up, with a lot of moving parts. If one of
the parts changes, it could fundamentally affect the resultant
forecast. Thus, overall forecast confidence is average to below
average and will need to continue to refine the forecast as we
head through tonight. One of the biggest forecast challenges
remains the question of how far north the warm air (greater
than freezing) intrudes into Southcentral. Based on better model
agreement with placement of large scale features on Wednesday,
have trended the forecast warmer, indicating a transition from
snow to rain across most of the Kenai Peninsula during the day
Wednesday followed by Anchorage and the Matanuska Valley late
Wednesday afternoon through Wednesday night.

Another critical forecast question is whether the Turnagain Arm
jet bends into Anchorage tomorrow afternoon. Multiple weak lows
will pass to the west across Southwest Alaska which is generally
favorable for winds bending into south to west Anchorage. However,
it appears a weak low persists farther south, helping to maintain
down Inlet pressure gradients which works against winds coming
into Anchorage. It's a precarious balance. If winds do move in,
then temperatures will jump up into the upper 30s or lower 40s
and precipitation will change to rain. If the winds stay over
the Inlet, temperatures will remain at or below freezing and
precipitation will fall as snow. Whatever precipitation does fall
should be light due to the strength of the southeasterly flow
across the Kenai and Chugach Mountains.

Expect the greatest impacts for travel tomorrow through tomorrow
night across the Kenai Peninsula and the Susitna Valley. The main
threat for the Kenai Peninsula will be snow, with blowing snow
also possible along the Homer Bluff in the morning. Snow will
change to rain from south to north, will cold air and snow holding
on longest in the Kenai area. Meanwhile, gusty easterly winds
will develop through Portage Valley, eastern Turnagain Arm, and
Turnagain Pass leading to snow and blowing snow beginning midday
Wednesday. Temperatures will warm as the winds increase, likely
changing to rain near sea level by Wednesday evening. However,
snow and blowing snow will persist through Wednesday night through
Turnagain Pass.

The heaviest snow will fall across the Susitna Valley thanks to
persistently very strong low level southerly flow. Expect periods
of light snow through Wednesday morning. Heavy snow will then
develop Wednesday afternoon and continue all the way through
Thursday. Flow will start to back to the southeast Thursday in
response to a deepening low south of Kodiak Island. This will
slowly shift the snow to the western Susitna Valley by Thursday
afternoon, with snow likely ending from Talkeetna southward. While
they have had numerous snow storms in the Susitna Valley this
winter, this looks like it will be the biggest snow producer thus
far, with one to two feet expected across nearly the entire zone.

&&

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

A frontal boundary over southwest Alaska will intersect another
boundary pushing north from the north Pacific early Wednesday
morning. Strong warm air advection from the Pacific front will
create a large area of rain across southwest Alaska and the Alaska
Peninsula, as well as create some gusty gap winds on Wednesday.
The lower Kuskokwim valley will record snow as enough cold air
will remain for precipitation to fall as snow. Snow amounts from
Sleetmute east will reach advisory levels with totals reaching 14
inches in some locales from Wednesday morning through Wednesday
night. Areas adjacent to the coast will see rain and some rain
snow mix as the front pushes through, but in the cold air behind
the front some scattered snow showers will be possible Thursday
for most of southwest Alaska.

&&

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

In the wake of the frontal boundary that passed through the Bering
on Monday and Tuesday, strong cold air advection and gusty winds
with isolated showers will persist over the Bering on Wednesday.
The north Pacific system continues to interact with the remnants
of the storm from Monday and will bring showers to the Alaska
Peninsula on Thursday. A brief period of ridging builds in over
the Bering on Wednesday night followed by the next system that
moves into the western Aleutians midday Thursday.

&&

.MARINE (Days 3 through 5)...

Friday a storm will bring gale to storm force winds to the
Eastern Aleutians, Alaska Peninsula and Western Gulf as one low
tracks east just south of the Gulf and another low to the west
drives a strong front across the Bering. A brief break between
storm systems should occur on Saturday; however, there is a fast
paced low expected to develop along the eastern Aleutians Saturday
afternoon. There is high uncertainty on the track an strength of
this system as it races toward the Gulf into Sunday.

&&

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

An active weather pattern will remain over Southcentral Thursday
night into Friday morning. A warm front associated with a low in
the Gulf combined with cold air over the region will create the
conditions possible for a wintry mix of precipitation throughout
southern Alaska.

A strong upper level jet looks to keep a warm front associated
with a low in the Gulf over Southcentral through the early to
middle part of the weekend. This warm front will take some time
to displace the cold air that will be over the region, leading to
a wintry mix of precipitation changing over to rain in some areas
by Friday evening. Friday evening, a low in the eastern Bering
looks to move inland late Friday night into Saturday morning
which would bring warmer temperatures and the possibility for a
wintry mix of precipitation to southwestern Alaska. A North
Pacific low late Saturday night seems as if it will move across
the Aleutians, bringing with it ample precipitation along with
some uncertainty on its track. This low may remain over the
eastern Bering Sunday night or it could make its way into the
northern Gulf towards Prince William Sound. Cold air could move as
far south as the Alaska Range Sunday night, dropping temperatures
once again, while warmer air looks to remain south of the Range
to end the extended forecast period. All in all, the unsettled
weather continues with impacts relating to precipitation types
across the entirety of the region due to warm and cold air masses
alternating as they move across the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning 145.
         Winter Weather Advisories 152 121 125.
MARINE...Gale Warning 412 150 155 160 172 185 119 120 125 130 131 132
					  136 137 139 141 351 352
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JER
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...LTB
MARINE/LONG TERM...KH/CK