Small Craft Advisory 1084, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AST SAT DEC 22 2007

.MODEL DISCUSSION...GFS MODEL OVERALL WILL BE USED FOR SHORT AND
MEDIUM RANGE FORECAST PACKAGE. MOST SIGNIFICANT CHANGE IS POSITION
AND PRESSURE OF A DEVELOPING LOW PRESSURE CENTER MOVING SOUTH OF THE
EASTERN ALEUTIANS SUN EVENING. LAST TWO RUNS OF THE GFS HAVE BEEN
SOMEWHAT CONSISTENT ON THESE FEATURES AND THE NAM IS WITHIN THE BALL
PARK. FOR NOW WILL TREND TOWARD THE GFS SOLUTION IN CURRENT GRIDS.

.ANALYSIS AND UPPER LEVELS...

970S LOW CENTER OVER BRISTOL BAY WAS INITIALIZED WELL BY THE GFS40
WITH VERIFICATION FROM THE PAKN RADAR. THIS CENTER WILL MOVE OFF
TOWARD THE SEWARD PENINSULA OVER THE NEXT 24-36 HOURS. TROUGH OVER
SOUTHCENTRAL AK THIS AFTERNOON MOVES INTO THE INTERIOR TONIGHT. EAST
AND SOUTH ADVANCEMENT OF COLD ADVECTION AND NORTHERLY FLOW IS EVIDENT
WITH OPEN CELL CU WHICH HAS SPREAD FROM THE BERING SEA TO OVER THE
EASTERN ALEUTIANS/AK PEN AND SOUTH. A SECONDARY LOW CENTER LIKELY TO
FORM SOUTH OF THE AK PEN AND BE CARRIED NE TO OVER THE EASTERN KENAI
PEN/WESTERN PRINCE WILLIAM SOUND SUN AFTERNOON. COLD ADVECTION ON
BACKSIDE OF CENTER LIKELY TO FOLLOW FROM THE SW. STRONG PRESSURE
RISES ON THE BACKSIDE OF THIS LOW WILL GENERATE FAIRLY STRONG SW
WINDS OVER SHELIKOF STRAIT AND COOK INLET SUN. RIDGE BUILDS AND
CONTINUES EAST THROUGH SUN NIGHT AS DEVELOPING NPAC LOW MOVES TO
SOUTH OF THE EASTERN ALEUTIANS/WESTERN AK PEN. THIS CENTER WILL
LIKELY BE IN THE LOWER 970S SUN NIGHT. POSITION SUN NIGHT AT 12Z
WOULD PUT THIS CENTER JUST SW OF SAND POINT. CONCERN IS THAT AS
CENTER TRAVELS SOUTH OF DUTCH HARBOR SUN EVENING...THAT SHORT
DURATION BLIZZARD CONDITIONS COULD DEVELOP OVER UNALASKA. FOR NOW
LOOKING AT A WATCH FOR THIS REGION. THIS CENTER MOVES SOUTH OF KODIAK
ISLAND MON AFTERNOON AND WEAKENS. SECONDARY CENTER LIKELY TO FORM
NEAR KODIAK ISLAND AND MOVE TO SHELIKOF STRAIT MON AFTERNOON. THIS
CENTER THEN MOVES INTO THE EASTERN GULF AND WEAKENS TUE AFTERNOON.
HIGH PRESSURE BUILDS OVER THE EASTERN BERING SEA MON AFTERNOON AND
SHIFTS OVER THE WESTERN HALF OF THE MAINLAND TUE. NEXT BIG STORM
ROLLS UP TO SW OF UNALASKA TUE AFTERNOON.

.EAST...SNOW SHOWERS...MIXED ALONG COASTS...WILL MOVE THROUGH
SOUTHCENTRAL/GULF TONIGHT. GAP WINDS OVER SOUTHCENTRAL WILL SETTLE
DOWN TONIGHT AS BRISTOL BAY LOW SHIFTS NW AND WEAKENS. ANOTHER SHOT
AT SNOW FOR SOUTHCENTRAL ON SUN AS LOW MOVES TO OVER THE WESTERN
KENAI PEN/W PRINCE WILLIAM SOUND TUE. THIS SYSTEM HAS FAIR POTENTIAL
AS SNOW PRODUCER FOR SOUTHCENTRAL WITH NEG TILTED UPPER TROUGH AND
STRONG COLD ADVECTION ON BACKSIDE. DETRACTOR IS THAT SYSTEM IS MOVING
FAIRLY QUICK AS STRONG RIDGE BUILDS ON THE BACKSIDE. MAIN AREA OF
PRECIPITATION WILL END WITH PASSAGE OF UPPER TROUGH SUN NIGHT. FOR
NOW WILL BUMP UP POPS AND INTRODUCE SNOW AMOUNTS AND SEE HOW THINGS
DEVELOP ON NEXT RUN.

.WEST...MAIN CONCERN WITH POTENTIAL FOR BLIZZARD CONDITIONS SUN NIGHT
OVER THE EASTERN ALEUTIANS WITH APPROACH OF NEXT STORM CENTER. SHOULD
BE FAIR AMOUNT OF SNOW AND WINDS ON THE BACKSIDE OF THIS CENTER WITH
OCCLUDED FRONT. POSITION OF CENTER IS STILL A LITTLE UNCERTAIN. FOR
NOW WILL GO WITH A BLIZZARD WATCH FOR THE EASTERN ALEUTIANS SUN
EVENING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH ZONE 185.
MARINE...GALES 120 130 132 AND 138. SEE MARINES FOR UPDATES.
FIRE WEATHER...NONE.

RMC DEC 07