Gale Warning 767, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
704 AM AKST Fri Dec 27 2019

.ANALYSIS AND UPPER LEVELS...

Conditions are much more quiet across Southcentral this morning.
Zonal mid-level flow is coinciding with drier air west of and
including Anchorage as is shown on current water vapor imagery. This
is leading to partial clearing over the region which has led to sub
zero temperatures across much of the Anchorage area this morning. A
weak surface low moving onshore west of Cordova is bringing light
snow to coastal areas as well as the Copper River Delta. This will
gradually taper off this morning before the next system approaches
by evening.

The main story over Southwest Alaska remains the dangerously cold
wind chills (near -50F in some areas). Strong high pressure over
Siberia combined with a number of lows in the North Pacific is
leading to gusty northeasterly winds across portions of the
Kuskokwim Delta and Bristol Bay. Wind Chill Advisories remain in
effect for these areas through noon Saturday.

A very active pattern continues over the Bering. Several low
centers in the North Pacific are bringing widespread easterly
gales leading to periods of blowing snow over the central
Aleutians and Pribilofs.

&&

.MODEL DISCUSSION...

Latest models continue to show the GFS as an outlier with regards
to the low approaching Kodiak Island. Other synoptic models as
well as the mesoscale models indicate a faster and farther
easterly track, thus making this the most likely outcome at this
time. In any case, snow and blowing snow is likely for the city of
Kodiak, though prolonged blizzard conditions appear unlikely. As
the low continues to track northeastward, significant snow
accumulations are likely from Whittier eastward towards Valdez and
the Copper River Valley. As with any forecast, uncertainties
exist as there is often one or more outlier models, however
confidence is not any lower than average in this particular case
and the aforementioned impacts are likely given this system
encompasses a large portion of the Gulf.

&&

.AVIATION...

PANC...VFR conditions and northerly winds near 10 kts will persist
through this evening. Though uncertainty exists regarding the exact
timing, snow will begin Saturday morning with visibilities causing
MVFR conditions and possible IFR conditions in heavier snow bands.

&&

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

A strong low will move northward through the Gulf later today and
tonight. This low will deepen to about 959 mb around midnight
tonight, then weaken as it tracks into Prince William Sound
Saturday morning. This storm will bring significant winds and snow
to Kodiak Island this afternoon through tonight. Both sides of the
Kenai Peninsula will also see some snow and winds, and Winter
Weather Advisories have been issued for those areas. Blizzard
conditions are expected in Thompson Pass tonight into Saturday
morning. Snow will spread inland tonight and Saturday morning,
with the highest amounts expected over the Copper River Basin.
Chances of snow will continue through Saturday night with cyclonic
flow aloft due to an upper low that will be moving into Southwest
Alaska.

&&

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

Brutally cold temperatures expected across the region as arctic
air holds in place. Overnight -35F was observed at Aniak and -19F
at King Salmon. Wind chill advisories have been issued for the
Kuskokwim Delta and Bristol Bay through Saturday afternoon. The
bone chilling temperatures will continue through the weekend.
Storms moving over the North Pacific will usher moisture into the
AKPEN and displace the arctic trough axis. Because the
temperatures associated with the arctic trough are so dangerous,
the position of the arctic trough is under constant monitoring.
Stay tuned for updates.

&&

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

The North Pacific is very active with mature lows near Northern
Japan and south of the Aleutians. The wet and windy pattern will
continue this forecast period. Models struggle with the tracks of
the surface lows, but all of the models show multiple fronts,
prolonged unsettled weather and gale to storm force winds at
times. Any breaks in the pattern that materialize will be short
lived.

&&

.MARINE (Days 3 through 5)...
(Sunday through Tuesday)

...Bering Sea and Aleutian Coastal Waters...

Low pressure south of the AKPEN and a second, stronger low well
south of the central Aleutians will continue to bring sustained
north-northeasterly gales across much of the Bering and westerly
gales south of the Chain through Tuesday. An area of storm-force
winds are also possible south of the eastern half of the Chain and
AKPEN late Monday into Tuesday depending on the strength and
position of the second low as it advances toward Bristol Bay. An
elevated likelihood for freezing spray, some of it heavy, will
persist into early next week. Seas in the 20 to 25 feet range will
transition from west to east for the forecast period. Winds and
waves are expected to relax by Tuesday across the western half of
the Bering and Aleutians as the storm activity moves toward the
southwest mainland.

...Gulf of Alaska...

Sustained gales, and perhaps a small area of storms, will persist
along the Southcentral coast Sunday as an area of low pressure
tracks northeast from near Kodiak to Prince William Sound. These
winds subside somewhat for Monday as the low and its front weaken.
A large area of westerly Small-Craft Advisory winds with embedded
storm-force winds will redevelop late Monday and continue into
Tuesday as a second low pressure system lifts toward the AKPEN with
a front moving across the Gulf. Seas will generally be in the 10 to
15 feet range near the coast, and 20 to 25 feet further offshore for
most of the forecast period.

&&

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

...Southcentral...

An active weather pattern will continue across Southcentral
through the end of the year. One storm system weakens on Sunday
with snowfall across the region and gusty winds along the coast
diminishing. The storm system then arrives quickly on the heels of
the previous, affecting the region Sunday night into Monday with
additional accumulating snowfall. Intrusions of rain, however, are
possible along the coast as some warmer air advects northward.

Yet another storm moves into the area for Monday night into
Tuesday. It is with this system that models begin to diverge
greatly on strength and track, and these significant differences
may play havoc on precipitation type and snow amount over a good
portion of Southcentral. Right now, it does appear that it will
remain just cold enough aloft that precipitation will stay all
snow over interior locations, with another round of accumulating
snow likely. However, enough warm air may move over the coast and
Cook Inlet that a changeover to a wintry mix (freezing rain) is
possible. That is what the latest GFS and ECMWF guidance is
indicating with 850mb (4,000ft above MSL) pushing 0C to +1C by
Monday evening. Snow showers then persist into Wednesday as this
system lifts north as cold air moves back in behind the low.

...Southwest Alaska...

An arctic trough diving south across Southwest Alaska will interact
with a storm system moving from near Kodiak Island to Prince William
Sound to bring a reinforcing shot of extremely cold air through
Sunday. By late Sunday, a low tracking north toward the AKPEN will
push warmer air and moisture over the region, resulting in
accumulating snowfall for the region. Enough warmer air aloft may
make it into the Upper Kuskokwim Valley for a brief changeover to
the wintry mix late Monday before this system lifts north and ushers
in another round of arctic air and continued snow showers into mid-
week..

...Saint Matthew Island, Pribilof Islands, and Aleutians...

Periods of snow showers will continue through next week with a
second round of arctic air diving south across the Bering by
Tuesday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning: 131.
         Winter Weather Advisory: 121 125 141 171.
         Wind Chill Advisory: 155 161.
         Flood Advisory: 145.
MARINE...Storm Warning: 119 174.
         Gale Warning: 120 121 125 127 128 130-132 136-139
                       150 155 160 165 170-173 175-181 185.
         Heavy Freezing Spray Warning: 139 150 160 165 179-181
                                       185.
FIRE WEATHER...NONE.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1024 AM AKST FRI DEC 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0834 AM     EXTR WIND CHILL  DUNKLE HILLS            63.30N 149.54W
12/27/2019  M-48 F           MATANUSKA-SUSITNA  AK   MESONET

            DUNKLE HILLS RAWS RECORDED A WIND CHILL
            VALUE OF -48F AT 8:34AM AKST.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1027 AM AKST FRI DEC 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0956 AM     EXTR WIND CHILL  WASILLA AIRPORT         61.57N 149.54W
12/27/2019  M-41 F           MATANUSKA-SUSITNA  AK   ASOS

            WASILLA AIRPORT ASOS RECORDED A WIND CHILL
            VALUE OF -41F AT 9:56AM AKST.

&&

ED

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
1029 AM AKST FRI DEC 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0956 AM     EXTR WIND CHILL  WASILLA AIRPORT         61.57N 149.54W
12/27/2019  M-41 F           MATANUSKA-SUSITNA  AK   ASOS

            WASILLA AIRPORT ASOS RECORDED A WIND CHILL
            VALUE OF -41F AT 9:56AM AKST.

0834 AM     EXTR WIND CHILL  DUNKLE HILLS            63.30N 149.54W
12/27/2019  M-48 F           MATANUSKA-SUSITNA  AK   MESONET

            DUNKLE HILLS RAWS RECORDED A WIND CHILL
            VALUE OF -48F AT 8:34AM AKST.

0754 AM     EXTR WIND CHILL  KING SALMON AIRPORT     58.68N 156.65W
12/27/2019  M-44 F           BRISTOL BAY        AK   ASOS

            KING SALMON AIRPORT ASOS RECORDED A WIND
            CHILL OF -44F AT 7:54AM AKST.

0856 AM     EXTR WIND CHILL  QUINHAGAK AIRPORT       59.76N 161.85W
12/27/2019  M-51 F           BETHEL             AK   ASOS

            QUINHAGAK ASOS REPORTED A WIND CHILL VALUE
            OF -51F.

0853 AM     EXTR WIND CHILL  BETHEL AIRPORT          60.78N 161.84W
12/27/2019  M-49 F           BETHEL             AK   ASOS

            BETHEL AIRPORT ASOS MEASURED A WIND CHILL OF
            -49F AT 8:53AM AKST.

0814 AM     EXTR WIND CHILL  SPARREVOHN              61.10N 155.57W
12/27/2019  M-42 F           BETHEL             AK   ASOS

            SPARREVOHN ASOS REPORTED A WIND CHILL OF
            -42F AT 8:14AM AKST.

0556 AM     EXTR WIND CHILL  ANIAK                   61.58N 159.54W
12/27/2019  M-44 F           BETHEL             AK   ASOS

            ANIAK AIRPORT ASOS REPORTED A WIND CHILL OF
            -44F AT 5:56AM AKST.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1033 AM AKST FRI DEC 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1104 PM     EXTR WIND CHILL  SNIPE LAKE              60.61N 154.32W
12/26/2019  M-50 F           LAKE AND PENINSULA AK   MESONET

            SNIPE LAKE MESONET RECORDED A WIND CHILL OF
            -50F AT 11:04PM AKST.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1038 AM AKST FRI DEC 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0956 AM     EXTR WIND CHILL  KWETHLUK AIRPORT        60.79N 161.44W
12/27/2019  M-46 F           BETHEL             AK   ASOS

            KWETHLUK AIRPORT ASOS REPORTED A WIND CHILL
            VALUE OF -46F AT 9:56AM AKST.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1043 AM AKST FRI DEC 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0900 AM     EXTR WIND CHILL  HOLITNA RIVER           61.40N 157.44W
12/27/2019  M-45 F           BETHEL             AK   MESONET

            HOLITNA RIVER STATION RECORDED A WIND CHILL
            VALUE OF -45F AT 9:00AM AKST.

&&

ED