FXAK68 PAFC 221338
AFDAFC

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKST TUE DEC 22 2009

.ANALYSIS AND UPPER LEVELS...
A BROAD UPPER LEVEL TROUGH REMAINS ENTRENCHED OVER THE BERING SEA AND
FAR WESTERN GULF OF ALASKA. A RAPIDLY AMPLIFYING RIDGE OVER THE
EASTERN GULF IS NOW REACHING WELL INTO THE ARCTIC OCEAN. BETWEEN
THESE TWO FEATURES IS A 100 KT JET COMING UP FROM THE SOUTH AND
BRINGING WARM AIR AND LOTS OF MOISTURE TO MAINLAND ALASKA.

AT THE SURFACE THERE IS A 955 MB LOW WEST OF SAINT MATTHEW ISLAND.
THE ASSOCIATED WEAKENING FRONT HAS PASSED THROUGH SOUTHWEST ALASKA
AND MOST OF SOUTHCENTRAL ALASKA AND IS STALLING OVER THE NORTH GULF
COAST. AHEAD OF THIS FRONT...MOST PRECIPITATION IS FALLING IN THE
FORM OF RAIN ALONG THE COAST AND PRINCE WILLIAM SOUND. MINIMUM GALE
FORCE WINDS ARE ALSO OCCURRING ALONG THE COAST AND WILL CONTINUE
THROUGH THIS AFTERNOON.

.MODEL DISCUSSION...
ON THE SYNOPTIC SCALE THE MODELS ARE IN RELATIVELY GOOD AGREEMENT FOR
THE REST OF THE WEEK IN KEEPING THE LONGWAVE TROUGH ANCHORED IN THE
BERING SEA...WITH A RIDGE HANGING ON IN THE EASTERN GULF. THIS WILL
ALLOW WARM AND MOIST AIR TO CONTINUE TO STREAM INTO THE STATE AND
WILL ALSO CONTINUE TO STEER MOST LOWS UP FROM THE SOUTH AND INTO THE
VICINITY OF KODIAK ISLAND AS THEY WEAKEN AND MOVE BACK TO THE WEST.
UNFORTUNATELY THE MODELS DO NOT AGREE AS MUCH REGARDING THE SURFACE
DETAILS OF THE NEXT LOW MOVING UP LATE TONIGHT AND WEDNESDAY MORNING.
CURRENT RUNS OF THE GFS AND UKMET BRING THE LOW TO NEAR SEWARD
WEDNESDAY MORNING...WHILE THE ECMWF...NAM...AND GEM MODELS ALL HAVE A
MORE SOUTHERLY TRACK THAT BRINGS THE LOW THROUGH THE BARREN ISLANDS
AND INLAND NEAR KAMISHAK BAY. DUE TO LINGERING UNCERTAINTY...AND THE
FACT THAT THE PREVIOUS FORECAST WAS BASED ON A MORE SOUTHERN
TRACK...WILL GENERALLY STICK WITH THAT SOLUTION FOR NOW...AND HOPE
FOR BETTER MODEL AGREEMENT IN THE NEXT RUNS.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...GUSTY WINDS WILL PERSIST TODAY THROUGH PORTAGE VALLEY
AND TURNAGAIN ARM...WITH MINIMUM GALE FORCE WINDS PERSISTING ALONG
THE NORTH GULF COAST AND IN SOUTHERN PRINCE WILLIAM SOUND. AS THE
FRONT MAKES SLOWLY PROGRESS NORTH AND EAST THE HEAVIEST PRECIPITATION
WILL SHIFT AWAY FROM THE KENAI PENINSULA AND UP INTO PRINCE WILLIAM
SOUND AND THE REST OF THE NORTH GULF COAST. PRECIPITATION IN VALDEZ
WILL STAY GENERALLY LIGHT DUE TO LOW LEVEL EASTERLY FLOW THAT BRINGS
A BIT OF DOWNSLOPING. TONIGHT...ALL EYES TURN TO THE STRONG
AFOREMENTIONED LOW THAT MOVES UP THROUGH THE CENTRAL GULF TOWARD THE
SOUTHERN KENAI PENINSULA AREA. DESPITE MODEL DIFFERENCES...CONFIDENCE
IS HIGH THAT STORM FORCE WINDS AHEAD OF THE ASSOCIATED FRONT WILL
MOVE INTO THE NORTH GULF COAST AREA OVERNIGHT TUESDAY. THE
DIFFERENCES IN THE MODELS ARE FAR MORE EXAGGERATED THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM....WHERE THE POTENTIAL EXISTS FOR A
SIGNIFICANT WIND EVENT ON WEDNESDAY. WILL NOT ISSUE ANY WATCHES OR
WARNINGS AT THIS TIME...ESPECIALLY CONSIDERING MODEL
DISAGREEMENT...BUT WILL HINT STRONGLY AT HIGH WINDS IN THE MORNING
FORECAST. 

.SOUTHWEST AND BERING SEA/ALEUTIANS...
STRONG LOW NEAR SAINT MATTHEW ISLAND WEAKENS RAPIDLY AND BECOMES A
COMPLEX LOW WITH MULTIPLE CENTERS IN THE NORTHWESTERN BERING TONIGHT.
MAIN IMPACT WILL BE SHOWER ACTIVITY THROUGHOUT THE AREA WITH
CONTINUED SMALL CRAFT AND MIN GALE SOUTHERLY WINDS IN THE EASTERN
BERING AND COOL NORTHWESTERLY WINDS FOR THE WESTERN ALEUTIANS.
TEMPERATURES WILL REMAIN ABOVE AVERAGE FOR THE NEXT SEVERAL DAYS.

.LONG TERM FORECAST...
MODELS SHOW LITTLE CHANGE IN THE LARGE-SCALE WEATHER PATTERN OVER THE
NEXT WEEK. RIDGING TO THE EAST WILL KEEP WARM AND MOIST SOUTHERLY
FLOW STREAMING INTO THE MAINLAND...AND THE PRIMARY STORM TRACK WILL
CONTINUE TO BRING LOWS UP INTO THE GULF AND THEN CURVE NORTHWEST INTO
SOUTHWEST ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...STORM WARNING 120 125 130
         GALE WARNING 128 132 138 140 141 150 160 180 185
FIRE WEATHER...NONE

AMD DEC 09