Blizzard Watch 4, NWS Anchorage, AK

647 
WWAK41 PAFC 100701
WSWAER

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
1001 PM AKST THU FEB 9 2017

AKZ125-102015-
/O.UPG.PAFC.BZ.A.0004.170210T1200Z-170211T2100Z/
/O.NEW.PAFC.WW.Y.0012.170210T1500Z-170211T1500Z/
WESTERN PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...WHITTIER...SEWARD...GIRDWOOD...
MOOSE PASS
1001 PM AKST THU FEB 9 2017

...WINTER WEATHER ADVISORY IN EFFECT FROM 6 AM FRIDAY TO 6 AM
AKST SATURDAY FOR PORTAGE VALLEY AND EAST TURNAGAIN ARM...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A WINTER
WEATHER ADVISORY FOR BLOWING SNOW...WHICH IS IN EFFECT FROM 6 AM
FRIDAY TO 6 AM AKST SATURDAY. THE BLIZZARD WATCH IS NO LONGER IN
EFFECT.

* LOCATION...THROUGH PORTAGE VALLEY AND EAST TURNAGAIN ARM.

* SNOW...5 TO 9 INCHES.

* VISIBILITY...MAY BE REDUCED TO ONE QUARTER OF A MILE OR LESS AT
  TIMES.

* WIND...WEST WINDS 25 TO 35 MPH WITH GUSTS TO 45 MPH.

*TIMING...WINDS WILL STEADILY INCREASE TONIGHT. WHILE SNOWFALL
 WILL BE LIGHT TONIGHT...WINDS WILL BE STRONG ENOUGH TO REDUCE
 VISIBILITY. SNOW WILL INTENSIFY TOWARDS MID-FRIDAY MORNING AND
 PERSIST THROUGH THE DAY...WHILE WIND SPEED WILL SLOWLY DIMINISH.
 EVEN AS THE WINDS DIMINISH...SNOWFALL WILL BE HEAVY ENOUGH TO
 REDUCE VISIBILITY. SNOW INTENSITY AND WIND STRENGTH WILL
 DIMINISH BY SATURDAY MORNING.

* IMPACTS...SNOWFALL COMBINED WITH STRONG WINDS AND BLOWING SNOW 
  MAY PRODUCE WHITE-OUT CONDITIONS AT TIMES. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY FOR BLOWING SNOW MEANS THAT
VISIBILITIES WILL BE LIMITED DUE TO STRONG WINDS BLOWING SNOW
AROUND. USE CAUTION WHEN TRAVELING, ESPECIALLY IN OPEN AREAS.

&&

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 AM AKST Thu Feb 9 2017

.ANALYSIS AND UPPER LEVELS...
A closed upper low is slowly moving southeast over Bristol Bay
bringing light snow to the southwest and localized areas of
Southcentral. A second low near Shemya moved a warm front into the
southwest Bering and central Aleutians with gale force southeasterly
winds and rain across the western Chain. The next significant low
pressure system originates from the arctic and is currently
diving south across the North Slope.

&&

.MODEL DISCUSSION...
Models are in relatively good agreement with the synoptic pattern
through Saturday morning, then diverge greatly in their solutions
late Saturday into early next week. The NAM and GFS were used to
make minor edits through Sunday morning. The general pattern into
the weekend is influenced by both polar and subtropical lows which
actively send multiple disturbances toward the southern area of
the state. This set up will bring ongoing precipitation into early
next week. A cold polar air mass moves over the eastern Bering and
across the southern mainland and Gulf keeping precipitation type
all snow with rain and snow along the western Aleutians changing
to snow by this weekend.

&&

.AVIATION...
PANC...
Low pressure crossing into the Gulf from Bristol Bay will bring
light snow this morning with dry conditions behind this system
during the afternoon. Snow development is expected again late
tonight as another polar low digs southeast toward the Kenai.
Visibilities and ceilings with the second system will need to be
monitored as there is still uncertainty with it's track and
timing through Friday.

&&

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

A couple of upper troughs dropping south across the northern Gulf
combined with strong low over the Gulf will continue elevated
chances of snow across Southcentral through Friday night. Snow
amounts are expected to be generally light across much of
Southcentral through Friday night. However, with model solutions
differing on the mesoscale features and resultant areal coverage
of QPF, there could be a some areas which see locally heavier snow
amounts. One of the keys for snow amounts across the Anchorage
Bowl/MAT Valley will be how much moisture pushes west across the
Chugach as the next upper low drops south across the northern Gulf
on Friday. These upper troughs will bring cooler air across the
region, intensifying surface pressure gradients and bringing
westerly gales to local storms across the western Gulf and brisk
outflow winds conditions over the eastern Kenai Peninsula this
afternoon in into Friday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The southwest mainland will begin a transition to a much colder
and predominantly dry pattern today as one trough departs into the
Gulf of Alaska and another quickly drops out of the arctic. The
arrival of this secondary trough will be accompanied by strong
cold air advection as 850 mb temperatures plummet by 10-15 degrees
C by early Friday morning. This will push temperatures well below
zero area-wide through Saturday, with the coldest temperatures
across the Lower Kuskokwim Valley and the Kuskokwim Delta.
Bitterly cold wind chill values will also become a concern across
these areas, however there is still uncertainty as to whether
winds will be strong enough for wind chills to reach advisory
criteria. Although the passage of the trough will be mostly dry,
some flurries may persist over interior southwest Alaska into
Friday night.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The front draped over the southwest Bering will continue to bring
periods of rain to the West/Central Aleutians as it gradually
weakens in place through Friday morning. Gale force winds will
generally diminish through today but will then be re-enforced
over the Central and Eastern Aleutians by Friday as a deepening
low brushes the Pacific side of the chain. Otherwise, increasing
northerly flow and cold advection associated with the digging
mainland trough will be the primary story across the remainder of
the Bering through Saturday. This will yield widespread Small
Craft Advisory level winds and freezing spray, along with
gradually increasing convective shower activity over much of the
region by Saturday afternoon.

&&

.LONG TERM FORECAST (Days 3 through 7)...
A cold longwave trough over interior Alaska will begin to drop
down over Southern Alaska Friday, bringing colder temperatures to
much of the region through Sunday. As this colder airmass settles
in over the area Friday, a surface low over the Gulf of Alaska
begins to strengthen and move over Prince William Sound. There is
good agreement in the models and higher confidence in precip
developing along the Northern Gulf coast areas and over parts of
the Copper River Basin Friday and into Saturday. However, models
are still struggling with the positioning of the surface low,
which has lead to lower confidence in snow potential/amounts over
the Anchorage, Mat-Su Valleys, and Western Kenai areas. One can
say with higher confidence that several areas of low pressure
will move into the Gulf of Alaska this weekend through the middle
of next week. Southerly flow associated with each of these
systems will help transport warm moist air from the Pacific
northward over the Southern Mainland. Even though confidence
remains low on the exact track of these systems, confidence is now
higher in warming temperatures and an overall wetter pattern for
the Southern Mainland next week.

Out west, a pattern change will also be underway over the Bering
Sea and northern Pacific, as the receding high pressure over the
areas gets pushes westward by the above mentioned cold longwave
trough tracking through the mainland. This will make way for the
upper level trough to set up over the Bering Sea and Northern
Pacific by early next week, with multiple systems at the surface
mainly staying along or south of the Aleutian chain through the
middle of next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Storms 130.
         Heavy Freezing Spray 121 127 129 130 136 137 138 150 160
         165 179 180 185.
         Gales 129 131 132 150 170 172 173 174 175 176 177.

&&

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...BC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...TP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1211 PM AKST THU FEB 09 2017

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

1159 AM     SNOW             3 E ANCHORAGE           61.21N 149.78W
02/09/2017  M4.0 INCH                           AK   NWS EMPLOYEE

            NWS EMPLOYEE REPORTS 4 INCHES STORM TOTAL IN THE LAST 12
            HOURS. STILL SNOWING LIGHTLY

&&

LINGRAM