Storm Warning 1, NWS Anchorage, AK

679 
FZAK62 PAFC 041241
OFFALU

Offshore Waters Forecast
National Weather Service Anchorage AK
341 AM AKST Fri Jan 4 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.

PKZ499-050215-
341 AM AKST Fri Jan 4 2019
.SYNOPSIS FOR CENTRAL BERING SEA...

A 978 mb low at 48N 174E and a 982 mb low at 52N 166E merge to 
form a 961 mb low near 55N 176E for Sat morning which then moves 
to 59N 175E at 971 mb by Sun morning. Its front moves over the 
Aleutians and Bering through Sun morning. A 969 mb low at 51N 173E
and its front approach the Western Aleutians for Sun morning.

$$

PKZ411-050215-
Bering Sea Offshore West of 180 and East of the International
Dateline-
341 AM AKST Fri Jan 4 2019

...GALE WARNING THROUGH SATURDAY...

.TODAY...SE wind 15 to 30 kt becoming E 25 to 40 kt in the
afternoon. Seas 8 ft building to 9 to 14 ft in the afternoon.
Rain.
.TONIGHT...E wind 30 to 45 kt. Seas 12 to 20 ft. Rain and snow.
.SAT...S wind 20 to 35 kt becoming SW 30 to 45 kt in the
afternoon. Seas 14 to 29 ft. Snow.
.SAT NIGHT...SW wind 25 to 40 kt. Seas 14 to 27 ft.
.SUN THROUGH MON...S wind 25 to 40 kt. Seas 13 to 21 ft.
.TUE...S wind 10 to 20 kt. Seas 10 to 14 ft.

$$

PKZ412-050215-
Bering Sea Offshore 171W to 180 and North of 56N-
341 AM AKST Fri Jan 4 2019

...GALE WARNING TONIGHT AND SATURDAY...

.TODAY...S wind 10 to 20 kt becoming SE 15 to 30 kt in the
afternoon. Seas 7 ft.
.TONIGHT...SE wind 30 to 45 kt. Seas 8 to 13 ft building to 11 to
19 ft after midnight. Rain with snow.
.SAT...SE wind 30 to 45 kt diminishing to 20 to 30 kt in the
afternoon. Seas 15 to 20 ft. Rain and snow.
.SAT NIGHT...S wind 20 to 35 kt. Seas 15 to 27 ft.
.SUN THROUGH MON...S wind 30 to 45 kt. Seas 15 to 25 ft.
.TUE...S wind up to 20 kt. Seas 10 to 16 ft.

$$

PKZ413-050215-
Bering Sea Offshore 171W to 180 and South of 56N-
341 AM AKST Fri Jan 4 2019

...GALE WARNING THROUGH SATURDAY...

.TODAY...SE wind 15 to 30 kt increasing to 25 to 40 kt in the
afternoon. Seas 6 ft building to 8 to 13 ft in the afternoon.
Rain.
.TONIGHT...S wind 25 to 40 kt. Seas 10 to 18 ft. Rain.
.SAT...SW wind 30 to 45 kt. Seas 13 to 28 ft.
.SAT NIGHT...SW wind 25 to 40 kt. Seas 18 to 29 ft.
.SUN...S wind 35 to 50 kt. Seas 16 to 25 ft.
.MON...SW wind 20 to 35 kt. Seas 14 to 20 ft.
.TUE...SW wind 10 to 20 kt. Seas 10 to 15 ft.

$$

PKZ414-050215-
Bering Sea Offshore East of 171W-
341 AM AKST Fri Jan 4 2019

...GALE WARNING TONIGHT AND SATURDAY...

.TODAY...W wind 15 kt becoming S in the afternoon. Seas 6 ft.
.TONIGHT...SE wind 15 to 30 kt increasing to 25 to 40 kt after
midnight. Seas 6 to 11 ft.
.SAT...S wind 25 to 40 kt. Seas 9 to 14 ft. Rain and snow.
.SAT NIGHT...SW wind 15 to 25 kt. Seas 9 to 17 ft.
.SUN THROUGH MON...S wind 25 to 40 kt. Seas 10 to 18 ft.
.TUE...S wind 10 to 20 kt. Seas 8 to 13 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
839 AM AKST Thu Jan 3 2019

.ANALYSIS AND UPPER LEVELS...
There is a vortex of cold air over Eastern Siberia, with this
frigid air pushing over the Bering. The models and the
ASCAT/advanced scatterometer data have detected several weak and
decaying surface lows over the Bering but the most organized lows
are well south of 50N. Not surprising, the jet core is also south
of 50N. The longwave trough clearly spans from Russia across the
Bering and into Western Alaska. Looking at the temperatures aloft
and at the surface, there is a blanket of Arctic air south of the
Aleutians, albeit slightly modified and a brutal cold airmass
over the interior. The radars at Bethel (PABC), Kenai (PAHG) and
Middleton Islands (PAIH) have snow showers on them early this
morning.

&&

.MODEL DISCUSSION...
The NAM, GFS and ECMWF are in decent agreement with the placement
of the synoptic features over the AKPEN, Southcentral and the Gulf
Of Alaska. By 00z Saturday, the same models rapidly bring a strong
low in the Western and Central Aleutians but there is no
consensus for the placement of the surface low on Saturday. The
GFS and the ECMWF have more similar tracks, but the NAM is an
outlier. This divergence in solutions is already present at 36hrs
which does not bode well for the remainder of the forecast package
especially for the zones west of 170W as the timing of the
gale/storm force winds and precipitation shield is a function of
the accuracy of the low.

&&

.AVIATION...
PANC...A band of light snow has moved into the region and the
ceiling dropped below 5,000 feet over night. Generally expecting
VFR conditions however, cannot rule out the possibility of brief
MVFR conditions based on the presence of low clouds on the AVHRR
satellite image over Knik Arm and portions of the northern Cook
Inlet.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The upper level trough is over the Talkeetna Mountains and into
Prince William Sound early this morning. It will continue to move
eastward today allowing the much colder air to the west to move
into the area. Temperatures will drop though the day over northern
Cook Inlet through the Susitna Valley as cloud cover decreases.

Some embedded short waves over the next few days may bring in
some periods of high clouds which could bump the temperatures up a
little as they are overhead, but it will be a generally cold
period.
Outflow winds will increase today but the pattern is not conducive
for extremely strong winds since there is no strong low in the
Gulf of Alaska. This will also keep the Matanuska River winds
that often occur during cold periods from occurring, at least for
the next few days.

&&

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

Parts of Southwest Alaska are getting a little bit of snow this
morning as a weakening front moves into the coast. The front is
producing snow showers over the Kuskokwim Delta near Bethel and
south along the coast to Dillingham this morning. Continued
weakening is expected for the rest of the morning which will
result in the snow showers diminishing as well as moving inland.
Otherwise, expect mostly cloudy skies and mainly dry conditions
across Southwest Alaska today as temperatures struggle into the
single digits and teens along the Kuskokwim Valley and 20s along
the coast. Tonight, another weak low and associated front will
restart the snow showers, once again mainly at the coast, though
some may drift inland, especially Friday morning. Once again none
of the snow showers are expected to be heavy or long in duration.
The snow showers will diminish into Friday evening.

&&

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

As expected, the Bering remains mostly quiet this morning, however
a few small, weak systems are producing snow showers in localized
areas, including the Pribilofs this morning. Those snow showers
will slowly weaken as they move into the eastern Bering today.
Otherwise, scattered snow showers are expected for the rest of the
Bering through tonight.

More active weather will begin across the Western and Central
Aleutians Friday morning in advance of a strong area of low
pressure approaching the islands. While at least a mix of snow and
rain is expected, temperatures should remain above freezing, so
any accumulations of snow will be minor. The primary weather
hazard with this storm are strong winds, which will be sustained
above 35 mph, especially the closer to the low you get. By Friday
evening, the center of the low will have crossed the chain into
the Western Bering. Cold advection to the south of the low will
cross the Aleutians, producing winds nearing 50 kt as the low
peaks in intensity Friday night. Gusts will near hurricane force,
and have been included in the forecasts at 60 kt by Saturday
morning. The leading front will approach the Pribilofs early
Saturday morning. While winds are likely to be at or above 35 kt
as it passes, for now it seems enough warm air will be present to
at least have a mix of rain and snow, and should it stay all snow,
temperatures will be in the mid 30s, which will limit any of the
snow being resuspended. Finally, the front will be through the
Pribilofs in 6 hours or less, so any reduced visibilities and
potential heavy snow will be brief.

&&

.LONG TERM FORECAST (Days 4 through 7)...

Beginning the extended period forecast on Saturday evening, there
will be a strong storm force low over the western Bering Sea and
associated upper low with a developing high amplitude blocking
high over Eastern Siberia. Over Southern Alaska, there will be a
series of weak upper level waves merging into a consolidated
trough. With time, the upper trough over the mainland will deepen
in response to the building blocking high over the high latitudes,
so this will keep a storm track over the Bering Sea with cold and
dry high pressure forming over Southern Alaska. This pattern will
last through Tuesday until high uncertainty develops with the
development and placement of an arctic low over Alaska. The ECWMF
and GFS both show a low, but the GFS favors a quicker transition
to southwest progressive flow from the Pacific which would
eventually bring in more precip threats as early as Tuesday
whereas the ECMWF favors a much colder and longer lasting dry
spell, through at least Wednesday. Due to the anomalous ECMWF
upper level pattern, and overall high uncertainty with developing
arctic lows, this forecast will trend in more precip threats
beginning Tuesday. Precipitation threats will likely be all snow
given the cold air which will be in place, but for now, there is
no strong signal.

&&

.MARINE (Days 3 through 5)...

Beginning the extended period marine forecast, the main impacts
will be a developing storm force low over the western Bering Sea
on Friday. The low track is now highly certain with a general
track moving along and then north of Attu Island. The front will
extend northward into the Bering on Saturday and may reach storm
force as the low tracks north. With an easterly component to the
winds, heavy freezing spray may become an issue closer to the ice
edge.

Another powerful storm force low is on track to move into the
western Bering again on Sunday and Sunday night. Confidence with
this second low is quite good, and model trends have remained
consistent.

In the Gulf of Alaska waters, with the storm track over the Bering
Sea, there is high confidence that winds will remain well below
gale force through the period.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...413 411 175 176 177.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...PJS
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW
MARINE/LONG TERM...DL