Gale Warning 539, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
210 AM AKDT TUE AUG 31 2010

.ANALYSIS AND UPPER LEVELS...
AN UPPER LEVEL LOW QUITE EVIDENT ON SATELLITE IS MOVING EAST THROUGH
BRISTOL BAY...RIDING THE NORTH SIDE OF THE UPPER LEVEL JET STREAM.
THIS UPPER LOW WILL MOVE INTO THE NORTHWEST GULF TODAY AND A WEAK
SURFACE LOW WILL FORM UNDERNEATH THE UPPER LOW IN THE NORTHERN GULF
TONIGHT.

HIGH PRESSURE DOMINATES THE BERING/ALEUTIANS...ALTHOUGH A FRONT WILL
MOVE INTO THE WESTERN BERING/ALEUTIANS FROM THE WEST TONIGHT AND
WEDNESDAY.

.MODEL DISCUSSION...
MODELS ARE IN FAIRLY GOOD AGREEMENT IN THE SHORT TERM...ALTHOUGH
PINPOINTING PRECIPITATION OVER SOUTHCENTRAL THE NEXT FEW DAYS WILL
BE DIFFICULT DUE TO SUBTLE DIFFERENCES IN UPPER LEVEL SHORTWAVES
ROTATING AROUND AN UPPER LEVEL LOW IN THE GULF OF ALASKA. ONE
DIFFERENCE REGARDS A WEAK UPPER LEVEL LOW THAT PINCHES OFF FROM THE
MAIN GULF LOW AND MOVES INTO THE UPPER TANANA VALLEY. THE NAM AND
ECMWF HAVE THIS FEATURE...BUT THE GFS DOES NOT. FAVORING THE
NAM/ECMWF AND GOING WITH LIKELY POPS OVER THE EASTERN COPPER RIVER
BASIN FOR WEDNESDAY AND WEDNESDAY NIGHT.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
ANOTHER INTERESTING FORECAST TODAY. AN UPPER LEVEL LOW WILL CROSS
THE ALEUTIAN RANGE AND MOVE INTO THE NORTHWEST GULF OF ALASKA TODAY
AND STALL OUT OVER THE NORTHERN GULF THROUGH WEDNESDAY. THIS UPPER
LOW...COUPLED WITH COLD AIR ALOFT...WILL HELP TO PRODUCE CONVECTION
OVER SOUTHCENTRAL. EXPECT GENERALLY SCATTERED SHOWER ACTIVITY WITH A
FEW THUNDERSTORMS INLAND. SOME SHOWERS COULD BE LOCALLY HEAVY LIKE
MONDAY/MONDAY NIGHT. A SHOWER ON MONDAY DROPPED JUST OVER HALF AN
INCH OF RAIN IN LESS THAN TWO HOURS OVER PORTIONS OF EAST
ANCHORAGE...AND A SHOWER MONDAY NIGHT OVER PALMER DROPPED 0.70 INCH
OF RAIN IN THREE HOURS.

NOT A LOT OF CHANGE FOR WEDNESDAY...WITH SCATTERED MAINLY
AFTERNOON/EVENING SHOWERS AND AN ISOLATED THUNDERSTORM. AS MENTIONED
IN THE MODEL DISCUSSION...THERE WILL BE A BETTER CHANCE FOR SOME
STEADIER RAIN OVER THE EASTERN COPPER RIVER BASIN WED/WED NIGHT IN
ASSOCIATION WITH AN UPPER LEVEL LOW OVER THE UPPER TANANA VALLEY.

THE UPPER LOW OVER THE NORTHERN GULF WILL KICK OFF TO THE EAST
WEDNESDAY NIGHT AND A WEAK RIDGE OF HIGH PRESSURE MOVES OVERHEAD.
HOWEVER...THE RIDGE QUICKLY PROGRESSES EAST LATE THURSDAY...AND A
NEW UPPER LEVEL TROUGH APPROACHING FROM THE WEST WILL PROVIDE THE
CHANCE FOR AFTERNOON/EVENING SHOWERS ON THURSDAY.

SOUTHWEST MAINLAND...
SOME LEFTOVER SHOWERS TODAY OVER BRISTOL BAY AND THE KUSKOKWIM
VALLEY...BUT EXPECT A GENERAL SLIGHT CLEARING/DRYING TREND AS THE
UPPER LEVEL LOW OVER INLAND BRISTOL BAY THIS MORNING MOVES INTO THE
GULF OF ALASKA AND A WEAK RIDGE OF HIGH PRESSURE MOVES OVERHEAD.
RAIN CHANCES RETURN TO THE SOUTHWEST MAINLAND LATE WEDNESDAY NIGHT
INTO THURSDAY AS A SYSTEM CROSSING THE BERING SEA MOVES ONSHORE. THE
BEST RAIN CHANCES WILL BE OVER THE KUSKOKWIM DELTA AND AREAS
NORTHWARD.

BERING SEA/ALEUTIANS/ALASKA PENINSULA...
HIGH PRESSURE DOMINATES THE REGION TODAY AND TONIGHT...WITH THE
USUAL WIDESPREAD LOW CLOUDS. A FRONT MOVES INTO THE WESTERN
BERING/ALEUTIANS LATE TONIGHT AND WEDNESDAY. HIGH PRESSURE HOWEVER
WILL MAINTAIN A STRONGHOLD FOR A BIT LONGER RIGHT ALONG THE EASTERN
ALEUTIANS/ALASKA PENINSULA AS THE INITIAL WEATHER FRONT PASSES TO
THE NORTH ACROSS THE BERING SEA FROM THE PRIBILOFS NORTH WEDNESDAY
NIGHT. A SECONDARY FRONT HOWEVER WILL EASILY SWEEP EAST THROUGH THE
ENTIRE REGION THURSDAY AND FRIDAY.

.LONG TERM FORECAST...
A DECENT FRONT WILL MOVE EAST THROUGH THE BERING SEA
THURSDAY/FRIDAY...PUNCHING INTO THE SOUTHWEST MAINLAND ON SATURDAY.
ECMWF HAS COME INTO LINE WITH THE GFS ON BRINGING A LOT OF THE
MOISTURE EAST AND ACROSS THE ALASKA/ALEUTIAN RANGE INTO SOUTHCENTRAL
ALASKA FOR SUNDAY AND SUNDAY NIGHT...SO ADDED A CHANCE OF RAIN TO
THE FORECAST FOR THIS PERIOD. THEN PERHAPS SOME CLEARING FOR
SOUTHCENTRAL EARLY NEXT WEEK. FOR THE BERING...HIGH PRESSURE BRIEFLY
BUILDS IN ON SUNDAY...FOLLOWED BY AN INCREASE IN UNSETTLED WEATHER
EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING ZONE 176 AND 411
FIRE WEATHER...NONE

FOISY AUG 10