Heavy Freezing Spray Warning 199, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST WED NOV 28 2012

.MODEL DISCUSSION...
GUIDANCE IS IN FAIRLY GOOD AGREEMENT TODAY. GENERALLY A PREFERENCE
FOR THE NAM WITH ITS BETTER HANDLING OF THE SMALLER SCALE DETAILS.

.ANALYSIS AND UPPER LEVELS...
THERE IS A LARGE UPPER LEVEL LOW OVER THE NORTHEAST PACIFIC WITH
ANOTHER LOW OVER THE NORTHWEST TERRITORIES OF CANADA. A STRONG RIDGE
ALONG 170 DEGREES WEST LONGITUDE TO 180 LONGITUDE STRETCHES FROM THE
TROPICS TO THE NORTH POLE. AN UPPER LEVEL LOW OVER THE KUSKOKWIM
VALLEY THAT IS SEMI-ATTACHED TO THE NORTHWEST TERRITORIES LOW IS
MOVING SOUTH AND IN THE PROCESS OF BEING "HANDED OFF" TO NORTHEAST
PACIFIC LOW. AN UPPER LEVEL SHORT WAVE OVER NORTHEAST ALASKA IS ALSO
MOVING SOUTHWARD.

.SHORT TERM FORECAST...
THE KUSKOKWIM LOW WILL SLIDE INTO THE WESTERN GULF OF ALASKA BY LATE
TONIGHT. THERE IS VERY LITTLE MOISTURE ASSOCIATED WITH THIS LOW AND
ITS MAIN EFFECT WILL BE TO INCREASE MID LEVEL COLD ADVECTION OVER
SOUTHERN ALASKA AND INCREASE THE SURFACE PRESSURE GRADIENT. THE
NORTHEAST ALASKA SHORT WAVE WILL MOVE INTO SOUTHERN ALASKA THURSDAY
MORNING THEN SLOW CONSIDERABLY OVER SOUTHERN ALASKA AS IT TRIES TO
"PINCH OFF" INTO A CLOSED LOW. THIS WILL BRING SIGNIFICANT MID LEVEL
COLD ADVECTION TO SOUTH CENTRAL ALASKA AND PUSH WINDS UP INTO THE
HIGH WIND CATEGORY OVER THE MATANUSKA VALLEY. BY FRIDAY MORNING THIS
LOW WILL MOVE INTO THE GULF OF ALASKA AND TRANSFER INTO THE GULF
LOW. THIS WILL LEAVE SOUTHERN ALASKA IN BROAD NORTHERLY UPPER LEVEL
FLOW INTO THE WEEKEND.

.LONG TERM FORECAST...
FOR LATER IN THE WEEKEND INTO EARLY NEXT WEEK THE PATTERN WILL
REMAIN BASICALLY THE SAME WITH THE RIDGE AXIS JUST EAST OF 180
DEGREES LONGITUDE. THE SUBTLE DIFFERENCE WILL BE A CARVING OUT OF AN
UPPER LEVEL LOW OVER SOUTHERN ALASKA WHICH WILL THEN MOVE INTO THE
GULF OF ALASKA. BUT THIS WILL INDEED BE SUBTLE FOR PRACTICAL WEATHER
AS GENERALLY DRY AND COLD CONDITIONS WILL CONTINUE FOR MOST OF
SOUTHERN ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 111.
MARINE...GALE WARNING 127 128 130 138 140 155 160 180.
FIRE WEATHER...NONE.

LUDWIG NOV 12