Blizzard Watch 18, NWS Anchorage, AK

569 
WWAK41 PAFC 121358
WSWAER

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
458 AM AKST SUN FEB 12 2012

AKZ125-130300-
/X.EXT.PAFC.BZ.A.0018.120213T0600Z-120213T1500Z/
WESTERN PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...WHITTIER...SEWARD...GIRDWOOD...
MOOSE PASS
458 AM AKST SUN FEB 12 2012

...BLIZZARD WATCH NOW IN EFFECT FROM THIS EVENING THROUGH LATE
TONIGHT IN PORTAGE VALLEY AND TURNAGAIN ARM...

THE BLIZZARD WATCH IS NOW IN EFFECT FROM THIS EVENING THROUGH
LATE TONIGHT IN PORTAGE VALLEY AND TURNAGAIN ARM. 

* LOCATION...PORTAGE VALLEY AND TURNAGAIN ARM.

* SNOW...3 TO 5 INCHES.

* VISIBILITY...POSSIBLY ONE QUARTER MILE OR LESS AT TIMES.

* WIND...EAST 35 TO 50 MPH.

* TIMING...WINDS WILL INCREASE BY MID EVENING AND MIX WITH SNOW TO
  CAUSE BLOWING SNOW. THESE CONDITIONS WILL PERSIST THROUGH THE
  NIGHT BEFORE IMPROVING TOWARD SUNDAY MORNING.

* IMPACTS...A BLIZZARD WATCH MEANS THERE IS A POTENTIAL FOR 
  FALLING AND/OR BLOWING SNOW WITH STRONG WINDS AND EXTREMELY 
  POOR VISIBILITIES. THIS CAN LEAD TO WHITE-OUT CONDITIONS AND 
  MAKE TRAVEL VERY DIFFICULT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WATCH MEANS THERE IS A POTENTIAL FOR FALLING AND/OR
BLOWING SNOW WITH STRONG WINDS AND EXTREMELY POOR VISIBILITIES.
THIS CAN LEAD TO WHITE-OUT CONDITIONS AND MAKE TRAVEL VERY
DIFFICULT.

&&

$$

AKZ131-130300-
/X.CON.PAFC.BZ.A.0018.120213T0900Z-120214T0300Z/
NORTHEAST PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...VALDEZ...THOMPSON PASS
458 AM AKST SUN FEB 12 2012

...BLIZZARD WATCH REMAINS IN EFFECT FROM LATE TONIGHT THROUGH
MONDAY AFTERNOON IN THOMPSON PASS...

A BLIZZARD WATCH REMAINS IN EFFECT FROM LATE TONIGHT THROUGH
MONDAY AFTERNOON IN THOMPSON PASS. 

* LOCATION...THROUGH THOMPSON PASS.

* SNOW...10 TO 14 INCHES FROM MIDNIGHT SUNDAY NIGHT THROUGH MONDAY AFTERNOON.

* VISIBILITY...POSSIBLY ONE QUARTER MILE OR LESS AT TIMES.

* WIND...SOUTHEAST 30 TO 45 MPH.

* TIMING...SNOW AND BLOWING SNOW WILL DEVELOP AROUND MIDNIGHT
  TONIGHT. CONDITIONS WILL IMPROVE BY LATE MONDAY AFTERNOON.

* IMPACTS...A BLIZZARD WATCH MEANS THERE IS A POTENTIAL FOR 
  FALLING AND/OR BLOWING SNOW WITH STRONG WINDS AND EXTREMELY 
  POOR VISIBILITIES. THIS CAN LEAD TO WHITE-OUT CONDITIONS AND 
  MAKE TRAVEL VERY DIFFICULT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WATCH MEANS THERE IS A POTENTIAL FOR FALLING AND/OR
BLOWING SNOW WITH STRONG WINDS AND EXTREMELY POOR VISIBILITIES.
THIS CAN LEAD TO WHITE-OUT CONDITIONS AND MAKE TRAVEL VERY
DIFFICULT.

&&

$$

146 
WWAK41 PAFC 121939
WSWAER

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
1039 AM AKST SUN FEB 12 2012

AKZ125-122045-
/X.CAN.PAFC.BZ.A.0018.120213T0600Z-120213T1500Z/
WESTERN PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...WHITTIER...SEWARD...GIRDWOOD...
MOOSE PASS
1039 AM AKST SUN FEB 12 2012

...BLIZZARD WATCH IS CANCELLED IN PORTAGE VALLEY AND TURNAGAIN
ARM...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS CANCELLED THE
BLIZZARD WATCH. 

AREAS OF SNOW AND BLOWING SNOW WILL DEVELOP THIS EVENING...HOWEVER
TEMPERATURES WILL REMAIN TOO WARM FOR BLIZZARD CONDITIONS TO DEVELOP.

$$

AKZ131-130745-
/X.UPG.PAFC.BZ.A.0018.120213T0900Z-120214T0300Z/
/X.NEW.PAFC.BZ.W.0030.120213T0900Z-120214T0300Z/
NORTHEAST PRINCE WILLIAM SOUND-
INCLUDING THE CITIES OF...VALDEZ...THOMPSON PASS
1039 AM AKST SUN FEB 12 2012

...BLIZZARD WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 6 PM AKST
MONDAY THROUGH THOMPSON PASS...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A BLIZZARD
WARNING...WHICH IS IN EFFECT FROM MIDNIGHT TONIGHT TO 6 PM AKST
MONDAY. THE BLIZZARD WATCH IS NO LONGER IN EFFECT. 

* LOCATION...THROUGH THOMPSON PASS.

* SNOW...10 TO 14 INCHES FROM MIDNIGHT SUNDAY NIGHT THROUGH 
  MONDAY AFTERNOON.

* VISIBILITY...ONE QUARTER MILE OR LESS AT TIMES.

* WIND...SOUTHEAST 30 TO 40 MPH.

* TIMING...SNOW AND BLOWING SNOW WILL DEVELOP AROUND MIDNIGHT 
  TONIGHT. CONDITIONS WILL IMPROVE BY LATE MONDAY AFTERNOON. 

* IMPACTS...SNOWFALL COMBINED WITH STRONG WINDS AND BLOWING SNOW
  WILL PRODUCE WHITE-OUT CONDITIONS. DRIVING WILL BE VERY
  DIFFICULT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING. FALLING AND BLOWING SNOW WITH STRONG WINDS
AND POOR VISIBILITIES ARE LIKELY. THIS WILL LEAD TO WHITE-OUT
CONDITIONS...MAKING TRAVEL VERY DIFFICULT. ALL TRAVEL AND OUTDOOR
ACTIVITY IS STRONGLY DISCOURAGED.

&&

$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1200 PM AKST SAT FEB 11 2012

.ANALYSIS AND UPPER LEVELS...A BROAD AND DEEP UPPER TROUGH EXTENDS
FROM EASTERN ASIA TO THE GULF OF ALASKA. MAINLAND ALASKA IS IN THE
TRANSITION ZONE BETWEEN THIS TROUGH AND A HIGH AMPLITUDE RIDGE
CENTERED OVER WESTERN CANADA. STORMS ARE DEVELOPING ALONG THE UPPER
JET AT THE BASE OF THE TROUGH AND CURVING NORTHWARD TOWARD WESTERN
ALASKA. THE PRIMARY WEATHER MAKER THIS MORNING IS A VERTICALLY
STACKED 960 MB LOW JUST SOUTH OF THE ALASKA PENINSULA WHICH IS
WEAKENING AS IT MOVES NORTHWARD TOWARD BRISTOL BAY. STRONG EASTERLY
FLOW IS PRODUCING DOWNSLOPE DRYING ACROSS MUCH OF SOUTHCENTRAL AND
SOUTHWEST ALASKA. THE HIGHEST IMPACT WEATHER IS ALONG THE OCCLUDED
FRONT ALONG THE NORTH GULF COAST. A BARRIER JET HAS FORMED AS
INDICATED BY 50KT WINDS AT BUOY 46061 NEAR HINCHINBROOK ENTRANCE.
THE FRONT HAS NEARLY STALLED...SO IT WILL TAKE TIME FOR WINDS TO
DIMINISH. MODERATE TO HEAVY PRECIPITATION WILL ALSO CONTINUE TODAY
IN THE PRINCE WILLIAM SOUND REGION. THE NEXT LOW TO AFFECT THE
MAINLAND IS JUST BEGINNING TO DEEPEN SOUTH OF THE ALEUTIANS.
WITHOUT MUCH MOVEMENT IN THE LONG-WAVE PATTERN EXPECT IT TO TAKE
A VERY SIMILAR TRACK TO THE CURRENT LOW.

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT THROUGH THE NEXT
THREE DAYS. THERE ARE SOME MINOR POSITION DIFFERENCES WITH LOW
CROSSING THE ALEUTIANS INTO THE BERING MONDAY NIGHT AND TUESDAY.
THE GFS SHOWS GREAT RUN-TO-RUN CONSISTENCY AND THE ECMWF HAS
TRENDED TOWARD THE GFS...SO IT IS PREFERRED FOR THIS LOW.

.SHORT TERM FORECAST...THE LOW NEAR THE ALASKA PENINSULA WILL
CONTINUE TO STEADILY WEAKEN AS IT MOVES NORTHWARD ACROSS BRISTOL
BAY TONIGHT. WINDS OUT AHEAD OF THE SYSTEM WILL QUICKLY DIMINISH
THIS AFTERNOON AND EVENING...BUT STRONG PRESSURE RISES BEHIND THE
SYSTEM MEANS STRONG SOUTHERLIES WILL SPREAD NORTHWARD ACROSS THE
ALASKA PENINSULA AND KODIAK ISLAND WATERS. WINDS THROUGH TURNAGAIN
ARM WIND AND HIGHER ELEVATIONS OF ANCHORAGE WILL DIMINISH THIS
AFTERNOON AS THE OCCLUDED FRONT PASSES BUT THEN INCREASE AGAIN
TONIGHT AS THE LOW MAKES NORTHWARD PROGRESS CAUSING THE EAST/WEST
PRESSURE GRADIENT TO INCREASE. AS THE LOW REACHES THE SAME LATITUDE
AS ANCHORAGE THE NORTH-SOUTH PRESSURE GRADIENT WILL SWITCH CAUSING
SOUTHERLY WINDS TO MOVE INTO TOWN. AS LOW LEVEL WINDS VEER TOWARD
THE SOUTH THE AFFECTS OF DOWNSLOPING WILL DIMINISH. MEANWHILE A
WEAK UPPER TROUGH WILL MOVE THROUGH DURING THE DAY SUNDAY AND BRING
A QUICK SHOT OF SNOW TO AREAS OF SOUTHCENTRAL AND SOUTHWEST ALASKA
CURRENTLY UNDER THE INFLUENCE OF DOWNSLOPE FLOW.

THE NEXT SYSTEM DEVELOPING OVER THE NORTH CENTRAL PACIFIC WILL TAKE
NEARLY A TRACK NEARLY IDENTICAL TO THE CURRENT SYSTEM...WITH VERY
SIMILAR IMPACTS. THUS...DOWNSLOPE WINDS ACROSS THE SOUTHERN MAINLAND
WILL STRENGTHEN ONCE AGAIN AS WE HEAD THROUGH SUNDAY AFTERNOON AND
EVENING. THIS SYSTEM WILL BE WEAKER AND FURTHER ALONG IN ITS LIFE
CYCLE. THEREFORE...NOT AS MUCH WARM AIR WILL ACCOMPANY IT NORTHWARD
AND PRECIPITATION WILL REMAIN SNOW WITH THE EXCEPTION OF KODIAK
ISLAND AND THE IMMEDIATE GULF COAST. WILL HAVE TO CONSIDER A
BLIZZARD WARNING FOR THE PORTAGE VALLEY/EAST TURNAGAIN ARM AREA
WHERE TEMPERATURES WILL RIGHT NEAR FREEZING. A SECOND DIFFERENCE
WITH THIS SECOND SYSTEM IS THE EAST-WEST PRESSURE GRADIENT ON THE
EAST SIDE OF THE SYSTEM WILL BE TIGHTER (THANKS TO A STRENGTHENING
SURFACE HIGH OVER SOUTHWEST ALASKA/WESTERN CANADA). THUS...EXPECT
TURNAGAIN ARM WINDS TO BE A LITTLE STRONGER (BUT BELOW WARNING
LEVEL). FINALLY...THE STRONGER SOUTHERLY FLOW IN THE UPPER LEVELS
WILL PUSH THE FRONT FURTHER ONSHORE BEFORE IT WEAKENS. THIS MAY
BRING MORE WIND INTO THOMPSON PASS AND PRODUCE A BLIZZARD. THIS
SYSTEM WILL EXIT TO THE NORTH MONDAY WITH SIMILAR WEATHER AS ON
THE BACK SIDE OF THE CURRENT SYSTEM.

A STRONG SHORT-WAVE WILL DROP INTO THE BACK OF THE LONG-WAVE
TROUGH SUNDAY AND LEAD TO DEVELOPMENT FURTHER WEST THAN THE FIRST
TWO SYSTEMS. AMPLIFICATION OUT AHEAD OF THIS LOW WILL CAUSE IT TO
BEND NORTHWARD TOWARD THE CENTRAL ALEUTIANS MONDAY AND INTO THE
SOUTH-CENTRAL BERING TUESDAY. MODELS INDICATE THIS LOW WILL BOMB
AS IT NEARS THE ALEUTIANS...WITH POTENTIAL FOR HURRICANE FORCE
WINDS...BUT IT IS TOO EARLY TO HAVE A WHOLE LOT OF CONFIDENCE
IN THAT.

.LONG TERM FORECAST...A DEEP UPPER LOW AND TROUGH WILL PERSIST
OVER THE BERING SEA FOR THE DAY 4 THROUGH 7 TIME PERIOD FOCUSING
MOST OF THE ACTIVE WEATHER OUT WEST. THE MAINLAND WILL BE ON THE
PERIPHERY OF THIS ACTIVITY...GENERALLY REMAINING ON THE QUIET
SIDE...THOUGH WITH THE CHANCE OF A WEAKENING FRONT MOVING IN
FROM THE WEST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...150 155.
         GALE WARNING...120 125 130 132 138.
FIRE WEATHER...NONE.

SEB FEB 12