Small Craft Advisory 966, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1235 PM AKST FRI DEC 5 2008

.ANALYSIS AND UPPER LEVELS...A HIGH AMPLITUDE WAVE PATTERN HAS
SET UP ACROSS THE HEMISPHERE WITH TROUGHS OVER EASTERN ASIA AND
THE BERING SEA...BOTH EXTENDING SOUTHWARD TO THE TROPICS...AND
RIDGES OVER THE WEST PACIFIC/FAR WESTERN BERING AND THE EAST
PACIFIC EXTENDING INTO THE WESTERN U.S. THERE IS NOW A SINGLE
CLOSED UPPER LOW CENTERED JUST SOUTHWEST OF THE PRIBILOF ISLANDS.
THE LOW SOUTH OF THE ALEUTIANS HAS OPENED INTO A TROUGH AND IS
NOW ROTATING NORTHEASTWARD AROUND THE PERIPHERY OF THE CENTRAL
BERING LOW. WEAK WAVES EMBEDDED WITHIN THE UPPER LEVEL SOUTHERLY
FLOW CONTINUE TO MOVE ACROSS THE SOUTHERN MAINLAND AND EASTERN
BERING SEA PRODUCING SHOWERS ACROSS THE REGION. WARMER AIR ALSO
CONTINUES TO PROGRESS NORTHWARD AND CHANGE PRECIPITATION TO RAIN.
STRONG NORTHERLIES CONTINUE ACROSS THE CENTRAL BERING SEA ON THE
BACK SIDE OF THE UPPER TROUGH AND THE GRADIENT IS TIGHTENING
FURTHER AS THE LOW NEAR THE PRIBILOFS DROPS SOUTH-SOUTHWEST AS
INDICATED BY BUOY 46035 WHERE WINDS ARE PEAKING AT 56KT.

.MODEL DISCUSSION...MODELS ALL INITIALIZED REASONABLY WELL WITH
SYNOPTIC FEATURES AND ARE IN GOOD AGREEMENT THROUGH THE BEGINNING
OF NEXT WEEK. ONLY MINOR ADJUSTMENTS WILL BE MADE IN THE FIRST
THREE DAYS OF THE FORECAST. MODELS HAVE TRENDED NORTH AND WEST
WITH THE TRACK OF THE PACIFIC LOW MOVING INTO THE GULF MONDAY
AND NOW FORM A SECONDARY LOW BACK OVER THE BARREN ISLANDS REGION.
IT IS TOO SOON TO COMPLETELY BUY INTO THIS SOLUTION...BUT WITH GOOD
AGREEMENT BETWEEN GFS AND ECMWF WILL TREND HEAVILY TOWARD THE NEW
TRACK AND INCREASE WINDS ACROSS THE GULF REGION.

.SHORT TERM FORECAST...

MAINLAND ALASKA...UPPER TROUGH WILL BECOME NEGATIVELY TILTED AS
WEAKENING LOW SOUTH OF THE ALASKA PENINSULA LIFTS NORTHWARD TOWARD
KODIAK ISLAND TONIGHT. THUS...VERTICAL MOTIONS WILL INCREASE AND
STEADIER PRECIPITATION WILL DEVELOP FROM KODIAK ISLAND TO BRISTOL
BAY THIS AFTERNOON AND SPREAD NORTHWARD ACROSS THE SOUTHERN MAINLAND
TONIGHT. PRECIPITATION WILL REMAIN MOSTLY RAIN EXCEPT FOR THE
KUSKOKWIM VALLEY AND COPPER RIVER BASIN AND UP ALONG THE ALASKA
RANGE. COOLING ALOFT WILL BEGIN LATE TONIGHT OVER NORTHERN SECTIONS
OF SOUTHWEST ALASKA AS THE LOW REACHES THE WESTERN GULF AND FLOW
SHIFTS AROUND TO THE NORTH. AS THE BERING LOW DROPS SOUTHWARD
TOMORROW THE WESTERN BERING RIDGE WILL BUILD ACROSS THE BERING SEA
TOWARD NORTHWEST ALASKA. THIS WILL RESULT IN A DRYING AND COOLING
TREND ACROSS SOUTHWEST ALASKA OVER THE WEEKEND. SOUTHCENTRAL ALASKA
WILL ALSO COOL...BUT THE REMNANTS OF THE LOW THAT MOVES INTO THE
GULF WILL PROVIDE A CONTINUED CHANCE OF LIGHT PRECIPITATION...WHICH
WILL BE MAINLY IN THE FORM OF SNOW BY SUNDAY. ON MONDAY A RAPIDLY
DEEPENING LOW WILL TRACK INTO THE GULF...BRINGING GALE TO STORM
FORCE WINDS ACROSS THE GULF AS WELL AS STRONG NORTHERLY GAP WINDS
ALONG THE NORTH GULF COAST. IT IS TOO EARLY TO NAIL DOWN THE DETAILS
OF THIS SYSTEM...BUT THERE IS POTENTIAL FOR THIS TO EVOLVE INTO A
MAJOR WINTER STORM ACROSS SOUTHCENTRAL ALASKA AS WE HEAD THROUGH
THE FIRST HALF OF NEXT WEEK.

BERING SEA/ALEUTIANS...EXPECT A BAND OF SOLID STORM FORCE WINDS
WEST OF THE LOW NEAR THE PRIBILOF ISLANDS AS IT TRACKS SOUTHWARD
TOWARD THE CENTRAL ALEUTIANS TONIGHT AND THEN SOUTH OF THE
ALEUTIANS SATURDAY. WINDS WILL QUICKLY DIMINISH SATURDAY AFTERNOON
AND NIGHT AS THE LOW TRACKS AWAY FROM THE REGION AND THE UPPER RIDGE
BUILDS ACROSS THE BERING SEA. THE EASTERN BERING WILL REMAIN ON THE
WARM SIDE OF THE STORM TONIGHT AND THE GRADUALLY COOL SATURDAY
THROUGH SUNDAY. A MODERATE FRONT WILL CROSS THE WESTERN BERING AND
ALEUTIANS SATURDAY NIGHT AND SUNDAY. OTHERWISE...CONDITIONS ARE
LOOKING RELATIVELY CALM FOR THIS TIME OF YEAR.

.LONG TERM FORECAST...THE EARLY TO MIDDLE OF NEXT WEEK IS LOOKING
MORE AND MORE LIKE A STORM WILL SET UP OVER SOUTHCENTRAL. THIS STORM
WILL CLEAR OUT HEADING TOWARD THE END OF THE WEEK. MODELS BECOME
VERY INCONSISTENT WITH THE EVOLUTION OF THE PATTERN FROM THIS POINT
ONWARD. GFS/ECMWF BOTH INDICATE A VERY PROGRESSIVE...BUT AMPLIFIED
PATTERN. THIS WOULD SUGGEST SOME EXTREMES...EITHER VERY WARM OR VERY
COLD...BUT NOT LASTING VERY LONG DO TO THE PROGRESSIVE FLOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...172 175.
         GALE WARNING...176 185.
         HEAVY FREEZING SPRAY WARNING...180 185.
FIRE WEATHER...NONE.

SEB DEC 08