Gale Warning 43, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
520 AM AKST SAT JAN 9 2010

.ANALYSIS AND UPPER LEVELS...AN UPPER LEVEL HIGH PRESSURE CONTINUES
TO SLOWLY WEAKEN OVER THE NORTH BERING SEA WITH AN ASSOCIATED RIDGE
THAT STRETCHES SOUTHEASTWARD INTO WESTERN CANADA. A BROAD LONGWAVE
TROUGH DIGS ACROSS THE NORTH PACIFIC WITH A BROAD LOW CENTERED
APPROXIMATELY 600 MILES SOUTH OF ATKA. SEVERAL SHORTWAVES AND WEAK
LOWS ARE CIRCULATING AROUND THIS MAIN CENTRAL LOW. AT THE
SURFACE...AN ELONGATED  REGION OF WEAK LOWS STRETCHES ALONG THE NORTH
PACIFIC SOUTH OF THE ALEUTIAN ISLANDS.  A SHORTWAVE STRETCHES TOWARDS
THE ALASKA PANHANDLE REGION WHILE A SHARPER SHORTWAVE REACHES INTO
PRINCE WILLIAM SOUND.

.MODEL DISCUSSION...MODELS ARE CURRENTLY DEPICTING FEATURES
WELL...WITH THE HIGHER RESOLUTION NAM CAPTURING PRECIPITATION FROM
THE SHORTWAVE CURRENTLY OVER PRINCE WILLIAM SOUND. A BLEND OF MODELS
WAS USED FOR THE SHORT TERM DUE TO THE RELATIVELY GOOD AGREEMENT.
MODELS BEGIN TO DIVERGE SIGNIFICANTLY IN THE MIDTERM BY WEDNESDAY
NIGHT AND CONTINUE TO DIVERGE IN THE LONG TERM. THE RECENT EUROPEAN
MODEL RUN DIVERGES FROM PREVIOUS MODEL RUNS WITH AN OVER-AGGRESSIVE
POOLING OF COOLER AIR FROM THE NORTH AND DEVELOPMENT OF A DRAMATIC
LOW OVER NORTH ALASKA. THEREFORE...THE GFS MODEL WAS RELIED UPON FOR
THE MIDTERM OVER MAINLAND ALASKA. HPC GUIDENCE WAS RELIED UPON FOR
THE LONG TERM.  HOWEVER...DUE TO THE GREAT DIVERGENCE IN CURRENT
MODEL
RUNS...CONFIDENCE IS CURRENTLY LOW OF MID AND LONG RANGES.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...A SHARP SHORTWAVE IS BRINGING PRECIPITATION AND GALE
FORCE WINDS ALONG THE SOUTHERN BOARDER OF PRINCE WILLIAM SOUND.  THIS
WAVE IS EXPECTED TO PROGRESS TO THE WEST THROUGH THE REST OF THE DAY
BRINGING THE CHANCE FOR RAIN AND SNOW SHOWERS TO THE EASTERN SHORES
OF THE KENAI PENINSULA AND STEADIER RAIN TO KODIAK ISLAND. ALTHOUGH
THE SHORTWAVE WILL WEAKEN THROUGHOUT THE DAY...GALE FORCE WINDS WILL
CONTINUE ALONG THE SOUTHCENTRAL COAST THROUGH SATURDAY. GALE FORCE
JETS WILL ALSO FORM WITHIN SHELIKOF STRAIT AND THE EASTERN COAST OF
KODIAK ISLAND SATURDAY. A SECOND STRONGER SHORTWAVE WILL APPROACH THE
REGION SUNDAY. WINDS WILL REACH STORM FORCE ALONG THE SOUTHCENTRAL
GULF COAST WHILE STORM FORCE JETS WILL FORM IN SHELIKOF STRAIT...
ALONG KODIAK ISLAND AND ALONG THE SOUTHERN SHORES OF THE ALASKA
PENINSULA BY SUNDAY MORNING. IN THE COPPER RIVER BASIN...TEMPERATURES
ARE EXPECTED TO CONTINUE TO DROP OVER THE NEXT SEVERAL DAYS AS COOLER
AND DRIER AIR POOLS INTO THE REGION FROM THE NORTHWEST. THE BUILDING
PRESSURE GRADIENT FROM COOLER INLAND AIR ALONG WITH NORTHEASTERLY
WINDS ALOFT WILL HELP TO GENERATE GUSTY WINDS THROUGH THE COPPER
RIVER DELTA...EASTERN PRINCE WILLIAM SOUND...AND THE MATANUSKA
VALLEY.

.SOUTHWEST/BERING...A WEAK SHORTWAVE PROGRESSING THROUGH THE ALASKA
PENINSULA TODAY WILL BRING A CHANCE FOR LIGHT SCATTERED SHOWERS WITH
GALE FORCE WINDS ALONG SOUTH COAST. MORE PERSISTENT PRECIPITATION
WILL OCCUR ALONG THE PENINSULA EARLY SUNDAY MORNING AS A STRONGER
DISTURBANCE APPROACHES. WINDS WILL APPROACH STORM FORCE ALONG THE
SOUTHERN ALASKA PENINSULA COAST BY SUNDAY AFTERNOON AND STAY STRONG
THROUGH THE EVENING. A STRONG UPPER LEVEL RIDGE AND HIGH PRESSURE AT
THE SURFACE WILL LIMIT THE IMPACT OF THESE PROGRESSING DISTURBANCES
ON THE SOUTHWEST MAINLAND. COASTAL STRATUS WILL BE LIMITED BY DRY
NORTHWESTERLY OFFSHORE FLOW ALONG THE COAST. THE PRESSURE GRADIENT
BETWEEN THIS SURFACE HIGH AND APPROACHING SHORTWAVE SUNDAY WILL
RESULT IN STRONGER NORTHWESTERLY FLOW.

.ALEUTIANS...A DISSIPATING SHORTWAVE WILL BRING THE POSSIBILITY OF
LIGHT SHOWERS FIRST TO THE EASTERN AND THEN THE CENTRAL ALEUTIAN
ISLANDS TODAY.  A SERIES OF WEAK DISTURBANCES WILL MOVE ACROSS THE
REGION OVER THE NEXT SEVERAL DAYS BRINGING THE CHANCE FOR SHOWERS BUT
NO STRONG WINDS ARE EXPECTED IN THE SHORT TERM.

.LONG TERM FORECAST...THERE IS UNCERTAINTY IN THE LONG TERM FORECAST
DUE TO THE DIVERGENCE OF THE MODEL RUNS. MODELS GENERALLY INDICATE
THE WEAKENING AND THEN REBUILDING OF THE UPPER LEVEL RIDGE OVER
WESTERN CANADA AND MAINLAND ALASKA BY THE END OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...126 127 128 140 155
           STORM...120 130 132 136 137 138 150
         HEAVY FREEZING SPRAY...180 185
FIRE WEATHER...NONE

ELN/JAM JAN 10