Winter Weather Advisory 3, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SUN JAN 23 2011

.MODEL DISCUSSION...MODELS ARE DOING WELL WITH THE OVERALL PRESSURE
PATTERN BUT THERE ARE SOME DETAILS IN THIS DYNAMICALLY COMPLEX SYSTEM
THAT ARE CAUSING SOME PROBLEMS. THE NAM SEEMS TO HAVE A BETTER HANDLE
ON THE ELONGATION OF THE WEATHER FRONT IN THE GULF OF ALASKA AS THE
GFS IS KEEPING IT MORE CONSOLIDATED TO THE WEST WHICH IS NOT MATCHING
UP TO WHAT IS BEING SEEN ON SATELLITE. THE GFS RECOVERS FROM THIS AND
WAS USED PAST THE FIRST DAY AND A HALF IN THE AFTERNOON FORECAST
PACKAGES.

.ANALYSIS AND UPPER LEVELS...THERE IS A BROAD UPPER LEVEL TROUGH OVER
THE CENTRAL BERING SEA WITH SOME UPPER LEVEL RIDGING OVER THE EASTERN
GULF OF ALASKA. THE MAIN JET STREAM IS SOUTH OF THE AREA AS IT COMES
OFF OF JAPAN AND FOLLOWS THE 35N PARALLEL BEFORE CURVING TOWARD THE
UPPER RIDGE IN THE GULF. THERE IS ALSO A JET STREAK AT 250 MB OVER
SOUTHERN ALASKA WHICH IS LIKELY A CONTRIBUTING REASON AS TO WHY THE
FRONT OVER SOUTHERN AND SOUTHWEST ALASKA HAS BEEN SO STRONG.
THE MAIN SURFACE LOW IS A LITTLE SOUTH OF DUTCH HARBOR AND WILL
SLOWLY MOVE INTO THE EASTERN BERING SEA. A KINK IN THE WEATHER FRONT
WAS OBSERVED ON SATELLITE THROUGHOUT THE NIGHT BETWEEN ATKA AND THE
PRIBILOF ISLANDS. THIS FEATURE ACCELERATED THE WINDS IN THE EASTER
BERING SEA TO HURRICANE FORCE EARLY THIS MORNING AND BROUGHT BLIZZARD
CONDITIONS TO THE PRIBILOF ISLANDS.
A TRIPLE POINT LOW NEAR KODIAK WITH A SIGNIFICANT WEATHER FRONT
ASSOCIATED WITH THIS LOW IS MOVING THROUGH THE GULF OF ALASKA AND
BRINGING STORM FORCE EASTERLY WINDS TO THAT AREA.

.SHORT TERM FORECAST...THE NORTH GULF COAST IS EXPERIENCING STRONG
EASTERLY WINDS AHEAD OF THE STRONG WEATHER FRONT THIS AFTERNOON.
WINDS WILL DIMINISH AS IT PUSHES THROUGH BUT ITS PASSING WILL ALSO
ALLOW PRECIPITATION TO BEGIN IN EARNEST OVER A LARGE PART OF THE
AREA. THROUGH THE DAY TODAY THERE HAS BEEN STRONG DOWNSLOPING OVER
THE AREA SUPPRESSING THE PRECIPITATION BUT THAT WILL CHANGE WITH
FRONTAL PASSAGE. THE TWO BIGGEST AREAS OF CONCERN FOR THIS EVENING
THROUGH THE OVERNIGHT PERIOD IN THE EAST ARE THOMPSON PASS AND
PORTAGE VALLEY THROUGH EASTERN TURNAGAIN ARM. FOR PORTAGE VALLEY AND
EASTERN TURNAGAIN ARM THERE ARE WINDS GUSTING OVER 60 MPH WITH
BLOWING SNOW. VISIBILITIES ARE NOT LOW ENOUGH FOR BLIZZARD CONDITIONS
BUT IT BEARS WATCHING THROUGH THE EVENING...OR UNTIL FRONTAL PASSAGE
WHEN THE TEMPERATURES WILL RISE AND TURN PRECIPITATION TO MOSTLY
RAIN.
IN THOMPSON PASS THE BLIZZARD WATCH WAS CANCELED SINCE WINDS AND
VISIBILITIES WILL MOST LIKELY NOT BE SEVERE ENOUGH FOR A
WARNING...HOWEVER THERE WILL BE REDUCED VISIBILITY OVERNIGHT THROUGH
THE PASS.
THE SUSITNA VALLEY IS ALSO EXPECTED TO SEE SIGNIFICANT SNOWFALL IN
THE NORTHERN AND WESTERN REGIONS OVERNIGHT AS THE SOUTHEAST FLOW
UPSLOPES ALONG THE ALASKA RANGE.
ROUGH WEATHER IS ALSO OCCURRING IN SOUTHWEST ALASKA AND THE EASTERN
BERING SEA. THE BLIZZARD WARNING IN THE PRIBILOF ISLANDS EASILY
VERIFIED WITH 70 MPH WINDS AND OVER 12 HOURS OF VISIBILITIES OF ONE
QUARTER MILE OR LESS. THE SOUTHWEST ALASKA COAST ALONG THE KUSKOKWIM
DELTA ALSO WARRANTED A BLIZZARD WARNING BEING ISSUED AS NUMEROUS
LOCATIONS WERE AT NEAR ZERO VISIBILITIES IN WINDS GUSTING FROM 55 TO
70 MPH. WIND CHILLS ARE AN ADDITIONAL HAZARD IN THIS AREA AS
TEMPERATURES HAVE REMAINED FROM ZERO TO 15 BELOW ALL DAY PRODUCING
WIND CHILLS FROM 45 BELOW TO 55 BELOW ZERO. WINDS SHOULD SLOWLY
DIMINISH OVERNIGHT IN THESE AREAS.

.LONG TERM FORECAST...WEATHER WILL SETTLE DOWN AFTER TODAY INTO THE
MIDDLE OF THE WEEK. A PERSISTENT LOW IN THE BERING SEA WILL KEEP SNOW
SHOWERS AROUND THAT AREA BUT WINDS WILL BE DIMINISHED. MORE MILD
TEMPERATURES WILL BE OVER SOUTH CENTRAL ALASKA AS THE FLOW WILL
REMAIN SOUTHERLY.
THE NEXT LARGE STORM LOOKS TO MOVE INTO THE ALASKA PENINSULA AND
EASTERN ALEUTIANS WEDNESDAY NIGHT AND THEN INTO KODIAK ISLAND AND
SOUTHWEST ALASKA THURSDAY. THIS IS A WARM SYSTEM THAT MAY QUICKLY
TURN TO RAIN IN THESE AREAS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY 145. WIND CHILL ADVISORY 155.
BLIZZARD WARNING 155 195.
MARINE...STORM 132.
GALE 120 125 129 130 138 140 150 155 165 170 172 175 179 180 185.
HEAVY FREEZING SPRAY 179 185.
FIRE WEATHER...NONE

JAN 11