Small Craft Advisory 5, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
754 AM AKST Wed Jan 1 2020

.ANALYSIS AND UPPER LEVELS...

A powerful arctic trough with origins from a very strong and deep
polar vortex is now situated over all of the Southern Mainland,
with the center over inland Bristol Bay and the trough axis
extending to the Kenai Peninsula and the North Gulf Coast. 850 hpa
temperatures (4000-4500 feet) across Southwest Alaska are a very
cold -28 to -32 C, with that arctic air blasting through the gaps
in the Alaska Range in excess of 50 knots. The strongest low level
cold air advection in many years has pushed up Cook Inlet, with
Anchorage dropping 13 degrees in one hour last evening. The day
started with record high temps, and the evening ended with heavy
snowfall. Early this morning, the main snow band is directly over
Anchorage, the Matanuska Valley, and Prince William Sound. Lighter
deformation band snow is still falling over the Lower Kuskokwim
Valley and interior Bristol Bay where steady snow has been occurring
the past two days. Finally, strong cold air advection continues over
the Bering Sea, with continued ice growth and very impressive and
strong snow streamers seen on satellite. These northerly flow snow
showers and gale force winds are continuing to support areas of
blowing snow and dramatically reduced visibility all across the
Bering Sea and southern Alaska Peninsula.

&&

.MODEL DISCUSSION...

The numerical models are in excellent agreement with the synoptic
pattern heading into the weekend as arctic high pressure settles
over the Southern Mainland. Low pressure near Kodiak is an area of
slight discrepancy, as well as a front moving over the western
Bering Sea/Aleutians Thu night and Fri, but these differences are
rather inconsequential to the sensible weather impacts. The
favored models were the GFS and NAM Nest. Forecast confidence is
high.

&&

.AVIATION...
PANC...Snow will continue to lighten through the day today,
although there is less confidence on how quick the CIGS rise.
Current TAF forecast is probably on the more optimistic side.
There is a possibility fog develops overnight tonight. Confidence
is very low, but the morning TAF package will introduce VCFG to
start the trend if confidence increases.

&&

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

The first day of 2020 will feature markedly different weather than
the last day of 2019. Cold air wrapping around low pressure
situated northeast of Kodiak Island has dropped temperatures and
brought snow to the western Gulf and up into Cook Inlet. Snowfall,
cold temperatures and strong winds will continue for Homer and
the Kachemak Bay area through at least the morning. Cold air
advection will continue to drop 850 mb (4000-4500') temperatures
to nearly -20C by this afternoon. This will cause surface
temperatures across Southcentral to continue to drop through this
afternoon. This cold air will also cause intense gap winds over
parts of the marine waters to include the Barren Islands and
Shelikof through this afternoon.

This afternoon the upper level trough will move north and allow
the upper levels to dry out. This drying aloft will be responsible
for shutting off the snowfall from earlier today for most inland
areas. Snow showers will continue over the Gulf and along the Gulf
Coast with cold air creating instability over the warmer waters. The
upper level low looks to remain stationary tonight into Sunday
morning which will leave behind cold temperatures and mostly dry
conditions. There is an outside chance for some fog around Knik
Arm early Thu morning with fresh cold and open warmer waters. An
associated upper level wave will move across the northern Gulf
Thursday causing more snow shower activity through Prince William
Sound.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

The main driver for the weather over the southwest mainland is
the upper trough that is settling into an upper low near King
Salmon. The surface low is over the Cook Inlet region up to the
Talkeetna Mountains that is rotating moisture around it over
southwest Alaska. Most of the moisture is being rung out on the
east side of the Alaska Range, although some of the mid and high
level moisture continues to cross over the Alaska range. More
important is the moisture advecting around the west side across the
Eastern Bering Sea to the Alaska Peninsula and along the western
Aleutian Mountains. This moisture influx coupled with strong cold
advection is fueling the snow squalls along the Alaska Peninsula
into the Aleutian Mountains. Bands of snow are streaming south along
the Bering Sea Coast as well, creating blizzard conditions along the
coast of the Kuskokwim Delta. These bands should move offshore in
the morning hours bringing an end to the blizzard conditions.

The 850 MB temperatures will drop into the -20s to -30s across
the southwest mainland through New Years day, keeping the surface
temperatures cold. This coupled with the north wind that is
expected to persist through Wednesday evening, especially west of
Bethel, and will likely keep wind chills around -45 along the
immediate coast and over Nunivak Island Wednesday evening. A weak
surface low drops over the Kuskokwim Delta Wednesday night. This
will result in the wind dropping off and eventually ending the
wind chill hazard.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

The northwest flow will persist across the central and eastern
Bering Sea and Aleutians through Thursday night resulting in widespread
snow showers as the cold air streams across the Bering Sea. The
frigid temperatures will continue to result in heavy freezing
spray across much of the eastern Bering Sea to the Alaska
Peninsula and eastern Aleutians. West of the northerly flow a
weak ridge will result in benign weather over the western Aleutians
Wednesday. A front pushes in from the North Pacific Thursday morning
that will likely bring gale force wind to the western Aleutians
Thursday and Friday. The frontal boundary rotates northeast and
slowly weakens through Friday allowing for the winds to diminish.
This front will bring snow to the western Aleutians. The combination
of the snow and wind may very likely produce blizzard conditions in
Shemya Thursday and Thursday night. Stay tuned to the forecast.

&&

.MARINE (From Tue Afternoon Discussion...Days 3 through 5: Friday
through Sunday)...

A relatively quiet weather pattern sets up for this time of year
all across Southern Alaska and the Bering. A low over the
southern Gulf of Alaska may get winds to gale force along the
North Gulf coast, southern Cook Inlet, the Barren Islands, and
Shelikof Strait on Friday. The low moves into the eastern Gulf of
Alaska Saturday, with a chance of some northwesterly gales through
the Barren Islands. A new North Pacific low may move into the
southern Gulf of Alaska on Sunday, but there is substantial model
disagreement, and confidence in that is low.

For the Bering, high pressure will keep all winds below gale force
all across the Bering Sea, with a possible exception of a dying
front over the western Aleutians early on Friday. Winds may
approach gale force in the western Aleutians Sunday night as a
strong low approaches.

&&

.LONG TERM FORECAST (From Tue Afternoon Discussion...Days 3
through 7: Friday through Tuesday)...

A much quieter weather pattern is setting up for much of Southern
Alaska in the long-term period as a cold air mass becomes firmly
entrenched across the area. This will divert the storm track from
being over us to instead staying south over the North Pacific with
any lows impacting the Panhandle. This is generally well-agreed
upon in the models.

With that said, there will still be a few storm systems that will
be worth watching. On Friday, a weak low will be centered off the
coast of Kodiak, over the southwestern Gulf. It will slowly move
eastward across the southern Gulf and into the eastern Gulf on
Saturday. Snow may impact Kodiak into Friday morning, though a
repeat of the near blizzard conditions of a few days ago does not
appear likely. On Sunday, a new North Pacific low may approach the
AK Pen and Kodiak, but there is poor model agreement on this.
There is much better agreement on the leading front of a strong
North Pacific low moving into the western Aleutians on Monday. The
front should slowly track across the southern Bering into
Tuesday.

Elsewhere, cold and dry will be the name of the game over mainland
Alaska, which means the main weather hazards will be strong gap
winds, particularly through Thompson Pass, but also possibly
through the Matanuska Valley. These winds coupled with the cold
air may lead to wind chill concerns, which unlike previous days,
will focus more on Southcentral, rather than Southwest Alaska.
Continued polar air pouring southward across the Bering on Friday
looks to diminish this weekend, to more light and variable winds.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 121 155 181.
	     Winter Weather Advisory 101.
         Flood Advisory 145
MARINE...Storm Warning 130 132.
		 Heavy Freezing Spray Warning 130-141 150 160 165 179 180-185 414.
         Gale Warning 131 138 139 150-174 178 179 180-185 352 412-414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...MSO/CK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
MARINE/LONG TERM...JW/CK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1123 AM AKST WED JAN 1 2020

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

1122 AM     SNOW             GOVERNMENT HILL ANCHORA 61.23N 149.86W
01/01/2020  E7.0 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            SPOTTER REPORTED 7 INCHES OF SNOW NEAR
            HOLLYWOOD DRIVE AND IVY STREET.

&&

MV

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
1139 AM AKST WED JAN 1 2020

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

1122 AM     SNOW             GOVERNMENT HILL ANCHORA 61.23N 149.86W
01/01/2020  E7.0 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            SPOTTER REPORTED 7 INCHES OF SNOW NEAR
            HOLLYWOOD DRIVE AND IVY STREET.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1227 PM AKST WED JAN 1 2020

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

1227 PM     SNOW             NWS ANCHORAGE           61.16N 149.98W
01/01/2020  M9.5 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            MEASURED 9.5 INCHES OF SNOWFALL.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
218 PM AKST WED JAN 1 2020

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

0128 PM     SNOW             GLEN ALPS               61.09N 149.70W
01/01/2020  E14.0 INCH       ANCHORAGE          AK   PUBLIC

            SPOTTER REPORTED 13-15 INCHES IN GLEN ALPS.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
220 PM AKST WED JAN 1 2020

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

0220 PM     SNOW             HILLSIDE                61.10N 149.72W
01/01/2020  E11.5 INCH       ANCHORAGE          AK   PUBLIC

            SPOTTER REPORTED 11.5 INCHES OF SNOW.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
301 PM AKST WED JAN 1 2020

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

0300 PM     SNOW             UPPER POTTER VALLEY     61.06N 149.76W
01/01/2020  M10.5 INCH       ANCHORAGE          AK   PUBLIC

            SPOTTER REPORTED 10.5 INCHES OF SNOW.

&&

ED