Gale Warning 551, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKDT MON AUG 24 2009

.ANALYSIS AND UPPER LEVELS...
A LARGE VERTICALLY STACKED LOW IS IN THE NORTHEAST PACIFIC AND IS
MOVING SLOWLY TOWARD THE ALASKA PANHANDLE. THE REMNANTS OF A FRONT
THAT CROSSED INTO SOUTHCENTRAL ALASKA FROM THE WEST HAS STALLED AS
EXPECTED AND IS BRINGING WIDESPREAD SHOWER FROM THE SUSITNA VALLEY TO
THE KENAI PENINSULA AND PRINCE WILLIAM SOUND. HIGH PRESSURE OVER THE
EASTERN BERING AND SOUTHWEST ALASKA HAS ALLOWED PARTIAL CLEARING AT
MANY LOCATIONS...HOWEVER THE MASSIVE CLOUD SHIELD FROM THE CENTRAL
BERING LOW IS RAPIDLY APPROACHING FROM THE WEST. THE LARGE SURFACE
LOW RAPIDLY TRANSITING THE BERING IS BRINGING GALE FORCE WINDS TO THE
CENTRAL ALEUTIANS. A WEAK SECONDARY LOW OFFSHORE THE KUSKOKWIM DELTA
HAS BROUGHT AN AREA OF LIGHT RAIN TOWARD BETHEL THIS MORNING.

.MODEL DISCUSSION...
THE MODELS ALL REMAIN IN GOOD AGREEMENT ON THE BASIC PATTERN FOR THE
NEXT SEVERAL DAYS. HOWEVER TIMING AND INTENSITY DIFFERENCES STILL
EXIST WITH REGARDS TO THE IMPACT OF FORMER TYPHOON VAMCO AS IT
PARALLELS THE ALEUTIANS MIDWEEK AND DROPS INTO THE LONGWAVE TROUGH IN
THE GULF. THE IMPACT OF FORMERLY TROPICAL SYSTEMS IS OFTEN
UNDERESTIMATED IN THESE SITUATIONS...THUS IT WOULD BE PRUDENT NOT TO
FLOUT CONVENTIONAL WISDOM ON THE MATTER. NOT SURPRISINGLY...A
DEFINITE STRENGTHENING TREND IS NOTED OVER THE PAST SEVERAL MODEL
RUNS REGARDING THIS FEATURE.

.SHORT TERM FORECAST...
.EAST OF THE ALASKA RANGE...
WIDESPREAD SHOWERS IN COOK INLET SHOULD TAPER TO SCATTERED SHOWERS BY
EARLY AFTERNOON...BUT WILL LIKELY PERSIST THROUGH THE EVENING OVER
PRINCE WILLIAM SOUND AND PARTS OF THE COPPER RIVER BASIN. ISOLATED
SHOWERS WILL REMAIN A THREAT ACROSS THE ENTIRE AREA UNTIL THE NEXT
CHANCE FOR SIGNIFICANT RAINFALL MOVES IN WEDNESDAY NIGHT. EXPECT
MOSTLY CLOUDY AND SEASONABLY COOL CONDITIONS TO CONTINUE FOR THE NEXT
SEVERAL DAYS.

.WEST OF THE ALASKA RANGE...
PERIODS OF LIGHT RAIN OVER THE KUSKOKWIM DELTA WILL LIKELY PERSIST
FOR MUCH OF THE DAY...WHILE THE REST OF SOUTHWEST ALASKA WILL SEE
ISOLATED SHOWERS WITH INCREASING CLOUDINESS. RAIN AND GALE FORCE
WINDS OVER THE ALEUTIANS AND BERING WILL MOVE EAST TODAY. THE LOW
WILL CROSS THE ALEUTIANS NEAR DUTCH HARBOR AND MOVE SOUTHEAST INTO
THE LONGWAVE TROUGH. AFTER A VERY BRIEF RESPITE...ALL EYES SHIFT TO
THE FORMER TROPICAL LOW IMPACTING THE WESTERN ALEUTIANS LATE TUESDAY
NIGHT AND THE REST OF THE BERING ON WEDNESDAY. AT THIS POINT WILL CAP
WINDS AT GALE FORCE AS THE LOW PASSES THROUGH THE REGION...BUT THE
POTENTIAL DEFINITELY EXISTS FOR STORM FORCE GUSTS. WILL BE MONITORING
THIS CLOSELY AND REFINING THE FORECAST AS NEW MODELS COME IN. AT THIS
TIME...CONFIDENCE IS RELATIVELY HIGH THAT THIS STORM WILL PASS FAR
ENOUGH TO THE SOUTH THAT MINIMAL IMPACTS ARE EXPECTED FOR THE
SOUTHWEST MAINLAND.

.LONG TERM FORECAST...
THE LONGWAVE TROUGH OVER MAINLAND ALASKA AND THE GULF OF ALASKA LOOKS
TO PERSIST THROUGH THE END OF THE WEEK. A SERIES OF LOWS CROSS THE
SOUTHERN BERING AND MOVE INTO THIS TROUGH...EACH TIME REINFORCING LOW
PRESSURE IN THE AREA. FORTUNATELY IT LOOKS LIKE THE BRUNT OF THESE
STORMS WILL STAY SOUTH OF THE MAINLAND...WITH THE MAIN IMPACT TO MOST
LOCATIONS BEING OCCASIONAL RAIN AND 20-30KT EASTERLY WINDS IN THE
GULF. STARTING THIS WEEKEND...IT LOOKS LIKE THE FOCUS OF STORMS MAY
SHIFT BACK TO THE BERING AS FLOW BECOMES MORE ZONAL...BUT THIS IS FAR
FROM CERTAIN AT THIS POINT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 170
FIRE WEATHER...NONE.

AMD AUG 09