Storm Warning 18, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1245 PM AKDT WED MAR 25 2009

.SHORT TERM...SATELLITE LOOP SHOWS A STRONG LOW IN THE WESTERN GULF
MOVES NORTHEAST TOWARDS KODIAK AND ASSOCIATED FRONT WRAPPING AROUND
THE LOW WITH A TRIPLE POINT JUST SOUTHEAST OF KODIAK. A WARM FRONT
EXTENDING SOUTHEASTWARD FROM THE TRIPLE POINT MARCHES ACROSS THE
GULF TOWARDS THE PANHANDLE. WELL AHEAD OF THE INCOMING FRONTAL
BOUNDARY...WINDS OVER THE PANHANDLE ARE PRETTY LIGHT WITH DECREASING
CLOUDINESS. MODELS ARE IN FAIR AGREEMENT WITH THE LOW IN THE WESTERN
GULF MOVES NE TO NEAR KODIAK BY LATE TONIGHT THEN WEAKENS OVER
PRINCE WILLIAM SOUND THROUGH THU NIGHT. WARM FRONT WILL CONTINUE TO
MOVE ACROSS THE EASTERN GULF AND SOUTHEAST ALASKA THROUGH THURSDAY.
THE 12Z RUN NAM12 IS WELL INITIALIZED AND WILL BE USED FOR TONIGHT
AND THURSDAY FORECASTS.

AS THE LOW DRIFTS NORTHEAST TO NEAR KODIAK LATE TONIGHT...WARM
FRONT WILL CONTINUE TO DRIFT ACROSS THE EASTERN GULF AND
CLOUDINESS INCREASES FROM THE YAKUTAT AREA THIS EVENING AND
SPREADS SOUTHEAST THROUGH THURSDAY. SNOW WILL DEVELOP OVER YAKUTAT
THIS EVENING THEN SPREAD SOUTHEAST THROUGH TONIGHT. AS WARMER AIR
MOVES INTO THE AREA...SNOW WILL MIX WITH RAIN OR TURN TO RAIN BY
LATE TONIGHT INTO THURSDAY. STRONG WINDS WILL ACCOMPANY THE FRONT
TO THE NORTHERN COASTAL AREAS INCLUDING YAKUTAT AND ELFIN COVE.
THE PROXIMITY OF THE LOW WILL LEAD AN ADVISORY LEVEL WIND GUSTS
FOR YAKUTAT TONIGHT AND WINDY CONDITIONS FOR NORTHERN PANHANDLE
COASTS. UPPER MARGIN GALE FORCE WILL AFFECT NORTHERN OUTSIDE
WATERS AND OFFSHORE TONIGHT. THEN THE GALE WILL EXPAND SOUTHEAST
THROUGH THURSDAY. THE GALE WILL REMAIN OVER THE OFFSHORE WATERS.
LARGE SWELLS WILL MOVE INTO THE OFFSHORE WATERS TONIGHT WITH VERY
ROUGH SEAS ACROSS THE EASTERN GULF.

.LONG TERM...THE CHANGES TO THE EXISTING LONG RANGE FCSTS WILL
BE SMALL. THIS INCLUDES THE OCEAN WAVE HEIGHTS IN THE EASTERN
GULF AS HIGH AS 33 FT FOR THU NIGHT AND FRIDAY. OUR FORECAST
DOMAIN WILL EXPERIENCE A SEQUENCE OF STRONG CYCLOGENETIC WAVES
MOVING NE TO THE GULF THROUGH THE NEXT SEVEN DAYS, AND THE ONLY
RELATIVELY DRY PERIODS WILL OCCUR WHEN THE WARM SECTOR RIDGES
AHEAD OF THESE WAVES PROVIDE TEMPORARY SUBSIDENCE. THE FIRST
SUCH BREAK SHOULD OCCUR SATURDAY AND SATURDAY NIGHT, AND THE
MODEL CONSENSUS IS GOOD AND NAEFS MSLP SPREAD IS SMALL.

AT THIS TIME A 500 MB LONG-WAVE TROUGH EXTENDS FM THE ARCTIC
OCEAN TO OVER A LINE FM BARROW TO DUTCH HARBOR AND S.  THE
FIVE-WAVE GFS DEPICTS THIS TROUGH AS INTENSIFYING WHILE MOVG
E AND REACHING A BETHEL TO COLD BAY LINE.  A STRONG THERMAL
CONTRAST WILL INTENSIFY IN THE NPAC WITHIN 1000 NM S OF THE
CHAIN.

A HIGHLY BAROCLINIC REGION EXISTS ON A LARGE SCALE
TO THE SW OF THE PANHANDLE, SEVERAL STRONG CYCLOGENETIC WAVES
WILL TRACK NE TO THE GULF. THE ONLY BREAK IN ONSHORE FLOW AND
WIDESPREAD PRECIP WILL BE DUE TO THE WARM SECTOR RIDGES AHEAD
OF THE DEVELOPING WAVES. THE FIRST SUCH CYCLOGENETIC SYSTEM IS
DETAILED IN THE SHORT RANGE SECTION ABOVE. A SECOND WILL
INTENSIFY EARLIER IN THE TRACK, DEEPENING TO BELOW 976 MB S
OF COLD BAY. THIS SECOND CYCLOGENETIC SYSTEM WILL PUMP UP A
STRONG WARM-SECTOR RIDGE ALOFT OVER THE CENTRAL GULF OF ALASKA
SATURDAY.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 6 PM THIS EVENING TO 3 AM AKDT THURSDAY FOR
     AKZ017.
MARINE...GALE WARNING FOR PKZ042-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011-012-021-022-031-033>036-041.

SJA/JBT