Small Craft Advisory 644, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT SAT AUG 15 2009

.MODEL DISCUSSION...MODEL SYNOPTIC SCALE INITIALIZATIONS OF MSLP AND
MOISTURE FIELD COMPARISON WITH WATER VAPOR IMAGE WAS REASONABLE.
FORECAST TRENDS THROUGH TUESDAY ARE IN FAIRLY GOOD AGREEMENT AND
REASONABLE. BIGGEST DIFFERENCE IN THE SHORT TERM IS THE WESTWARD
EXTEND OF THE PRECIPITATION SHIELD IN SOUTHCENTRAL TONIGHT. THE GFS
BRING MOISTURE WELL INTO COOK INLET TONIGHT...WHERE AS THE NAM HOLDS
IT FURTHER EAST. OTHER MODELS SHOULD A WELL DEFINED SOUTHWESTERLY
FLOW OVER SOUTHCENTRAL TONIGHT...SO WILL LEAN WITH THE GFS
PRECIPITATION FORECAST TO TONIGHT.

.ANALYSIS AND UPPER LEVELS...

.500MB...GENERALLY STAGNATE PATTERN BECOMES A LITTLE MORE PROGRESSIVE
OVER THE NEXT COUPLE OF DAYS AS THE RIDGE OVER THE EASTERN GULF
SHIFTS EAST AND FLATTENS AND LOW CENTER OVER THE RUSSIAN ARCTIC MOVES
TO ALONG 150W AND THE ARCTIC OCEAN LATE TUE. BY TUE...THE LONG WAVE
TROUGH CURRENTLY EXTENDING FROM THE ALASKA ARCTIC TO THE LOW CENTER
OVER THE EASTERN BERING SEA..MOVES EAST TO BETWEEN 150-160W. BY WED
NIGHT...THE LONG WAVE MOVES TO ALONG 140-145W...A RIDGE BUILDS ALONG
160W...AS A LOW CENTER MOVES TO EASTERN RUSSIA.

.SHORT TERM...
...EAST...RAIN SHOULD INCREASE AGAIN OVER MUCH OF SOUTHCENTRAL ALASKA
TONIGHT AND SUN WAS MOISTURE SURGE ACCOMPANYING SWLY FLOW MOVES FROM
THE GULF OF ALASKA. WEAK SURFACE CENTER ALONG THIS BOUNDARY MAKES
LANDFALL ALONG THE NORTH GULF SUN. PRECIPITATION SHOULD BECOME MORE
SHOWERY SUN AND MON AS TEMPS COOL ALOFT. GUSTY WINDS IN THE ANCHORAGE
BOWL AND ALONG THE NORTH GULF COAST SHOULD DIMINISH LATE THIS
AFTERNOON. N/S PRESSURE GRADIENT WILL HOLD BRISK SOUTHERLY WINDS IN
THE COPPER RIVER BASIN THROUGH THIS EVENING.

.SW MAINLAND...UNSETTLED WEATHER WITH SHOWERS/RAIN LIKELY TO BE THE
CASE OVER INLAND SW ALASKA THROUGH SUN AS THE UPPER THROUGH
PROGRESSES EAST. GENERALLY LOW CLOUDS AND FOG WILL BE THE CASE ALONG
COASTAL LOCATIONS...ESPECIALLY OVER THE DELTA TONIGHT AND SUN AS HIGH
PRESSURE BUILDS OVER THE AREA. FOG/STRATUS LIKELY TO CONTINUE OVER
COASTAL SW ALASKA THROUGH MON...MORE BREAKS INLAND AS UPPER TROUGH
MOVES THROUGH. ANOTHER SHOT AT RAIN COMES MON NIGHT AND TUE AS A
WEATHER FRONT MOVES OVER THE DELTA/WESTERN BRISTOL BAY.

.BERING SEA...LOW COMPLEX OVER THE SOUTHERN BERING SEA DRIFTS SOUTH
OF THE ALEUTIANS SUN. HIGH PRESSURE BUILDS OVER THE AREA TONIGHT
THROUGH SUN NIGHT...SO WOULD EXPECT FOG AND STRATUS TO BE THE MAIN
WEATHER FEATURES. A WEATHER FRONT MOVES ACROSS THE NORTHERN AND
EASTERN BERING SEA MON NIGHT. THIS WILL LIKELY WILL BRING A LITTLE
RAIN...BUT WILL DO LITTLE TO DISSIPATE THE LOWER CLOUDS AND FOG.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC......FLOOD ADVISORY ZONE 121
MARINE...NONE.
FIRE WEATHER...NONE.

RMC AUG 09