Wind Chill Advisory 24, NWS Anchorage, AK

501 
WWAK42 PAFC 201312
WSWALU

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
412 AM AKST THU DEC 20 2012

AKZ152-210215-
/X.CON.PAFC.WC.Y.0024.000000T0000Z-121221T0300Z/
LOWER KUSKOKWIM VALLEY-
INCLUDING THE CITIES OF...ANIAK...SLEETMUTE
412 AM AKST THU DEC 20 2012

...WIND CHILL ADVISORY REMAINS IN EFFECT UNTIL 6 PM AKST THIS
EVENING FOR AREAS ABOVE 1000 FT...

* LOCATION...AREAS ABOVE 1000 FT ELEVATION

* WIND...NORTH WIND 20 TO 35 MPH

* WIND CHILL VALUES...35 TO 45 BELOW ZERO

* TIMING...STRONG WINDS ABOVE 1000 FT AND BELOW ZERO TEMPERATURES
  WILL CONTINUE TO CREATE DANGEROUSLY LOW WIND CHILLS THROUGH EARLY EVENING...WHEN
  WINDS WILL BE DIMINISHING.

* IMPACTS...INCREASED RISK OF HYPOTHERMIA AND FROSTBITE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS
WILL COMBINE TO GENERATE LOW WIND CHILLS. THIS WILL RESULT IN
FROSTBITE AND LEAD TO HYPOTHERMIA IF PRECAUTIONS ARE NOT TAKEN.

&&

$$

DEK

162 
WWAK42 PAFC 201709
WSWALU

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
809 AM AKST THU DEC 20 2012



AKZ152-201815-
/X.CAN.PAFC.WC.Y.0024.000000T0000Z-121221T0300Z/
LOWER KUSKOKWIM VALLEY-
INCLUDING THE CITIES OF...ANIAK...SLEETMUTE
809 AM AKST THU DEC 20 2012

...WIND CHILL ADVISORY IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS CANCELLED THE WIND
CHILL ADVISORY. 



$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
100 PM AKST WED DEC 19 2012

.ANALYSIS AND UPPER LEVELS...
THE ZONAL UPPER LEVEL PATTERN THAT HAS PREVAILED FOR THE BETTER PART
OF A WEEK IS TRANSITIONING THIS MORNING. THE JET STREAM THAT HAD
REMAINED SOUTH OF THE STATE HAS BUCKLED AND A SIGNIFICANT RIDGE IS
BUILDING ACROSS THE BERING SEA. AT THE SAME TIME...A LONGWAVE TROUGH
IN THE EASTERN GULF IS ALSO AMPLIFYING IN RESPONSE TO THE BUILDING
RIDGE OUT WEST. BETWEEN THESE FEATURES...STRONG NORTHWESTERLY WINDS
ARE OCCURRING ACROSS THE ALASKA PENINSULA. THE TIGHT PRESSURE
GRADIENT STRETCHING FROM THE ALASKA PENINSULA TO THE NORTH GULF COAST
IS BEING ENHANCED BY COLD AIR ADVECTION MOVING IN FROM NORTHWEST
CANADA AND INTERIOR ALASKA. FAVORED TERRAIN GAPS AROUND SOUTHCENTRAL
ARE INCREASING SIGNIFICANTLY TODAY. THE GULF LOW FROM YESTERDAY IS
NOW WEAKENING AND MOVING SOUTHWARD INTO THE PACIFIC...WHILE A
MODERATE STRENGTH FRONT OVER THE FAR WESTERN BERING IS MAKING ONLY
SLOW PROGRESS EASTWARD DUE TO THE STRENGTH OF BERING SEA HIGH
PRESSURE.

.MODEL DISCUSSION...
MODELS ARE IN VERY GOOD AGREEMENT THROUGH THE MAJORITY OF THE SHORT
TERM FORECAST PERIOD (FIRST 84 HOURS). THIS IS NOT SURPRISING
CONSIDERING THE AMPLIFIED AND RELATIVELY SLOW-MOVING FEATURES THAT
WILL BE CONTROLLING THE WEATHER OVER THE COMING DAYS. THE NAM IS THE
FAVORED MODEL EAST OF THE ALASKA RANGE...DUE PRIMARILY TO ITS ABILITY
TO DEPICT STRONG WINDS INTERACTING WITH COMPLEX TERRAIN. FOR THE
BERING SEA REGION...NO STRONG PREFERENCE WAS NOTED AMONG THE
MODELS...AND THE GFS WAS USED TO MAKE ONLY MINOR OVERALL CHANGES TO
THE FORECAST.

.SHORT TERM FORECAST...
THE PRIMARY FORECAST CHALLENGE OVER THE NEXT FEW DAYS WILL DEFINITELY
BE TIMING AND INTENSITY OF GAP WINDS ACROSS THE USUAL SUSPECT AREAS.
THIS INCLUDES THOMPSON PASS...WHITTIER...SEWARD...AND THE MATANUSKA
VALLEY. OF THESE AREAS...THE MOST CHALLENGING WILL LIKELY BE THE
MATANUSKA VALLEY WHERE A STRONG SURFACE-BASED TEMPERATURE INVERSION
IS CURRENTLY PROTECTING THE LOWER ELEVATIONS FROM THE STRONG WINDS.
AS A WEAK UPPER LEVEL DISTURBANCE MOVES INTO THE AREA LATE THIS
EVENING...THINK THE WINDS SHOULD BEGIN TO MIX DOWN TO THE SURFACE.
ONCE THIS HAPPENS...THE MAT VALLEY SHOULD JOIN THE OTHER LOCATIONS IN
REMAINING WINDY THROUGH THE END OF THE WEEK. THE PROCESS FORCING THE
STRONG WINDS THROUGH THURSDAY MORNING IS PRIMARILY A LOW-LEVEL
PROCESS CONSISTING OF A STRONG SURFACE PRESSURE GRADIENT AND ONGOING
WEAK COLD AIR ADVECTION. THESE TWO ATMOSPHERIC FORCING MECHANISMS
WILL BEGIN TO DIMINISH DURING THE DAY THURSDAY...HOWEVER UPPER LEVEL
WINDS WILL INCREASE OUT OF THE NORTH AT THE SAME TIME...WHICH SHOULD
BE THE CATALYST THAT KEEPS WINDS GOING THROUGH THE END OF THE WEEK.
THERE IS A POSSIBILITY THAT THESE TWO EVENTS MAY OVERLAP ENOUGH TO
BUMP A FEW OF THE CHANNELED AREAS TO NEAR-WARNING LEVEL GUSTS. THIS
SCENARIO LOOKS INCREASINGLY LIKELY AROUND VALDEZ...AND A HIGH WIND
WARNING WILL BE ISSUED SHORTLY. NEAR THE MATANUSKA
VALLEY...CONFIDENCE IN A SIMILAR INCREASE IN WIND SPEEDS REMAINS
LOW...AND THE FORECAST WILL GENERALLY MAINTAIN WIND SPEEDS THAT ARE
CURRENTLY ADVERTISED IN THE FORECAST.

SOUTHWEST...EXTREMELY COLD TEMPERATURES AND GUSTY NORTHWEST WINDS
WILL BOTH MODERATE OVER THE NEXT 24 HOURS AS THE BERING SEA RIDGE
MOVES INTO THE AREA. SKIES WILL REMAIN SUNNY THROUGH THE END OF THE
WEEK AS WINDS GRADUALLY BECOME OFFSHORE BY FRIDAY. THE FRONT
CURRENTLY AFFECTING THE ALEUTIANS WILL STALL BEFORE MAKING IT TO THE
SOUTHWEST COAST ON FRIDAY. OVERALL A RELATIVELY PLEASANT SECOND HALF
OF THE WEEK IS ON TAP.

BERING SEA AND ALEUTIANS...A SERIES OF FRONTS WILL PUSH THROUGH THE
WESTERN ALEUTIANS AND ATTEMPT TO PROGRESS EASTWARD THROUGH FRIDAY.
THE RIDGE CURRENTLY OVER THE BERING SEA WILL NOT STALL...BUT WILL
MOVE VERY SLOWLY. THIS WILL CAUSE THESE WEATHER FRONTS TO WEAKEN
SUBSTANTIALLY AND STALL BEFORE MAKING IT TO THE ALASKA PENINSULA.
EACH FRONT WILL BRING A PERIOD OF STRONG GALE-FORCE WINDS TO THE
WESTERN AND CENTRAL ALEUTIANS...THOUGH TEMPERATURES WILL BE WARM
ENOUGH TO AVOID ANY BLIZZARD CONCERNS...AND PERHAPS EVEN SWITCH MANY
LOCATIONS OVER TO RAIN THROUGH THE END OF THE WEEK.

.LONG TERM FORECAST...
LONG RANGE MODELS CONTINUE TO DEPICT THE BERING RIDGE MORPHING INTO A
POWERFUL CLOSED UPPER HIGH BY EARLY THIS WEEKEND. HOWEVER...THE HIGH
WILL NOT BE FAR ENOUGH SOUTH TO KEEP COLD AIR AND CLEAR SKIES ACROSS
ALL OF THE MAINLAND. ALL MODELS SUGGEST...THOUGH DIFFER SLIGHTLY ON
TIMING...THAT A STRONG UPPER LOW WILL MOVE WESTWARD OUT OF CANADA
TOWARD THE SOUTHERN MAINLAND BY SUNDAY. THIS WILL BRING CLOUDS AND
THE CHANCE OF SNOW BACK TO MOST AREAS OF SOUTHCENTRAL...WHILE
TEMPERATURES REMAIN BELOW NORMAL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 131 135
         WIND CHILL ADVISORY 131
MARINE...STORM WARNING 127 150
         GALE WARNING 121 126 128 129 130 132 155 170 172 175 176 179
                      185
FIRE WEATHER...NONE

DIXON DEC 12