Gale Warning 626, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1230 PM AKDT FRI SEP 11 2009

CORRECTED TYPOS

.ANALYSIS AND UPPER LEVELS...SYSTEM OVER THE NORTHERN GULF
CONTINUES TO WEAKEN. UPPER LEVEL LOW IS IN THE MIDST OF OPENING
UP INTO A TROUGH AND EXITING TO THE NORTHEAST WHILE THE SURFACE
LOW DRIFTS OFF TO THE NORTH. A TIGHT GRADIENT REMAIN AROUND THE
NORTH TO WEST SIDE OF THE LOW...WITH OBSERVATIONS AND QUIKSCAT
WINDS INDICATING A SOLID GALE WITH A SMALL AREA OF STORM FORCE
WINDS OFF THE COAST OF CAPE SUCKLING. MIDDLETON ISLAND SHOWS THE
BULK OF RAIN ROTATING THROUGH CORDOVA INTO SOUTHERN PRINCE WILLIAM
SOUND. THERE IS ALSO SOME RAIN OR SHOWERS ALONG THE REMNANTS OF
THE OCCLUSION WHICH EXTEND NORTHWESTWARD FROM THE NORTH END OF
KODIAK ISLAND TO ALONG THE ALASKA RANGE. IT IS TURNING OUT TO
BE A NICE ACROSS OTHER PORTIONS OF SOUTHCENTRAL AS EVIDENCED BY
VISIBLE SATELLITE IMAGERY WHICH SHOWS AN AREA OF CLEARING FROM
THE COPPER BASIN TO ANCHORAGE...CAUSED BY THE SHIFT IN MEAN FLOW
FROM SOUTHEAST TO NORTHEAST.

AN AREA OF STRATUS AND FOG HAS SETTLED IN ALONG PORTIONS OF THE
SOUTHWEST COAST AND EASTERN BERING UNDERNEATH A SHORT-WAVE RIDGE.

OUT WEST A LONG-WAVE TROUGH EXTENDS FROM EASTERN RUSSIA TO THE
CENTRAL BERING...WITH MULTIPLE WEAK LOWS EMBEDDED WITHIN. OF
MOST PERTINENCE TO ALASKA WEATHER IS A 990S SURFACE LOW A FEW
HUNDRED MILES NORTH OF THE WESTERN ALEUTIANS WITH OCCLUDED FRONT
EXTENDING SOUTHEASTWARD TO THE EASTERN ALEUTIANS. THIS ENTIRE
SYSTEM IS PROGRESSING EASTWARD ACROSS THE BERING SEA.

.MODEL DISCUSSION...MODELS ARE IN FAIR AGREEMENT WITH CONTINUED
DIFFERENCES IN EXACT LOW POSITIONS WHICH FOR THE MOST PART HAVE
VERY LITTLE IMPACT ON THE OPERATIONAL FORECAST. THERE IS ALSO
GOOD RUN-TO-RUN CONSISTENCY...SO WILL STICK CLOSE TO CURRENT
FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE SURFACE LOW WILL DISSIPATE AS IT MOVES
TOWARD PRINCE WILLIAM SOUND TONIGHT AND SATURDAY...KEEPING MOST
OF THE STEADY RAIN OR SHOWERS ALONG THE COAST. THE REMNANTS OF THE
OCCLUSION ALONG WITH A WEAK UPPER SHORT-WAVE SITTING OVER SOUTHWEST
ALASKA WILL MOVE EASTWARD TONIGHT AND COMBINE WITH MARGINAL
INSTABILITY (PRODUCED BY LOW-LEVEL HEATING IN SUNSHINE ACROSS
PORTIONS OF SOUTHCENTRAL WITH FAIRLY COLD AIR ALOFT) TO PRODUCE
ISOLATED TO SCATTERED SHOWERS ACROSS THE REGION. THE BERING SEA
SYSTEM WILL TRACK FROM THE EASTERN BERING SOUTHEASTWARD TO THE
NORTHEAST PACIFIC BY MONDAY. WEAK UPPER WAVES ALONG THE PERIPHERY
OF INFLUENCE OF THIS SYSTEM WILL CONTINUE TO MOVE ACROSS SOUTHCENTRAL
THE NEXT FEW DAYS...AIDING IN INITIATION OF A FEW SHOWERS.
HOWEVER...WITH GENERALLY WEAK DYNAMICS AND INSTABILITY THERE
SHOULD STILL BE PERIODS OF SUN AS WELL.

SOUTHWEST ALASKA...ONSHORE FLOW WILL CONTINUE TO ADVECT STRATUS
AND FOG INLAND OVER SOUTHWEST ALASKA TONIGHT. THE FLOW IN BRISTOL
BAY WILL SHIFT FROM DUE WEST TO SOUTHWEST WHICH WILL SHOULD ALLOW
STRATUS TO MAKE IT INTO DILLINGHAM AND KING SALMON. THE BERING SEA
SYSTEM WILL THEN QUICKLY BRING RAIN INTO THE REGION SATURDAY. AS
THE SYSTEM DROPS SOUTHWARD SUNDAY AND WINDS SHIFT TO OFFSHORE
THINGS WILL START TO IMPROVE...ALTHOUGH UPPER WAVES ROTATING
AROUND THE PERIPHERY OF THE SYSTEM WILL MAINTAIN A THREAT OF
SHOWERS THROUGH MONDAY.

BERING SEA/ALEUTIANS...AS THE LOW MOVES TO THE EASTERN BERING
ON SATURDAY A RIDGE WILL BUILD OVER THE WESTERN BERING AHEAD
OF ANOTHER STORM APPROACHING FROM THE WEST PACIFIC. THIS WILL
INTENSIFY NORTHERLIES ON THE BACK SIDE OF THE SYSTEM...AFFECTING
THE CENTRAL BERING DOWN ACROSS THE CENTRAL AND EASTERN ALEUTIANS
THROUGH SUNDAY. THE NEXT STORM WILL THEN QUICKLY MOVE TO THE
WESTERN ALEUTIANS BY LATE SUNDAY AND TAKE A MORE SOUTHERLY TRACK
AS IT PROGRESSES EASTWARD THE BEGINNING OF NEXT WEEK.

.LONG TERM FORECAST...GOOD MODEL CONTINUITY WITH SYNOPTIC SCALE
FEATURES CONTINUE THROUGH THE EXTENDED FORECAST PERIOD. THE ALEUTIAN
SYSTEM WILL DIVE SOUTHEAST INTO THE NORTH PACIFIC MID WEEK WHILE
THE SYSTEM OVER THE NORTHEAST PACIFIC EARLY IN THE WEEK LIFTS BACK
NORTHWARD TOWARD SOUTHCENTRAL (AS RIDGE BUILDS DOWNSTREAM). THUS...BY
THE END OF NEXT WEEK A SINGLE HIGH AMPLITUDE TROUGH WILL BE CENTERED
OVER WESTERN ALASKA...RESULTING IN A SHOWERY REGIME AND A BREAK FROM
MAJOR STORMS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...171 172 175.
FIRE WEATHER...NONE.

SEB SEP 09