Small Craft Advisory 113, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
153 PM AKST MON FEB 2 2009

.SHORT TERM...DEVELOPING LOW OVER THE NE PAC WILL TRACK NNE TO
NEAR PASI BY 12Z TONIGHT...THEN BE NNE OF PAJN BY 18Z TUE. ANOTHER
LOW WILL REMAIN OVER THE NW GULF THROUGH TUE. UPPER TROF WILL
SLIDE THROUGH THE AREA TUE. USED THE 12Z GEM MODEL FOR THE MAIN
LOW TRACK AS IT WAS THE BEST COMPROMISE AMONGST THE MODELS.

MAIN CONCERNS WILL BE POTENTIAL FOR STRONG WINDS OVER THE S...AND
HEAVY SNOW OVER THE N AND HYDER AREAS. A STRONG SSE LOW LEVEL JET
WILL ACCOMPANY THE LOW TO THE SE OF THE TRACK...AND FORECAST 850 MB
WINDS OF 60 TO 75 KT WILL LIKELY MEAN HIGH WIND CONDITIONS FOR THE
FAR SRN AREA...AND WIND ADVY CONDS FOR THE REMAINING SRN ZONES.
DECIDED TO GO WITH A HIGH WIND WARNING FOR ZONES 27 AND 28 FOR
09Z-15Z TONIGHT. WIND ADVY CONDS WILL LIKELY PRECEDE AND FOLLOW
THE WARNING TIME FRAME IN THESE ZONES BUT DO NOT WANT TOO MANY
HEADLINES FOR THE SAME PHENOMENA. WILL ISSUE WIND ADVYS FOR SRN
ZONE 23...26...AND SW COAST OF ZONE 29 FOR TONIGHT AND EARLY TUE.
ONCE THE TRAILING COLD FRONT MOVES THROUGH TUE MORNING...WINDS
SHOULD DROP BELOW ADVY LEVELS IN MOST AREAS...ALTHOUGH SOME
LOCALIZED ADVY LEVEL W-NW WINDS ARE POSSIBLE ALONG THE OUTER COAST
FROM PASI SWD LATER TUE MORNING.

ON THE N SIDE OF THE LOW...PRECIP WILL LIKELY FALL AS SNOW AND QPF
IS SUFFICIENT FOR HEAVY SNOW OVER MUCH OF THE NRN THIRD OF THE
AREA. THE ONE AREA THAT WILL BE TRICKY WILL BE AROUND PAJN...AS
LOW TRACK MIGHT ALLOW ENOUGH WARMING IN LOWER LEVELS FOR A MIX FOR
A FEW HOURS OVERNIGHT...BUT AS LOW MOVES PAST PAJN AROUND DAYBREAK
TUE...PRECIP SHOULD GO RIGHT BACK TO ALL SNOW AND IT WILL STILL BE
ON THE HEAVY SIDE WITH MID-LEVEL DEFORMATION BAND MOVING THROUGH AND
UPSLOPE FLOW OCCURRING. THE OTHER AREA OF CONCERN WILL BE NEAR
HYDER. PRECIP THERE WILL BECOME VERY HEAVY TONIGHT AND WITH WINDS
LIKELY TO BE LIGHT...ALLOW A HEAVY WET SNOW TO FALL THERE THROUGH
TUE MORNING. ONCE FLOW TURNS SW LATER TUE AFTER FROPA...SHOULD SEE
MORE MIXED PRECIP OR JUST RAIN IN HYDER.

OTHERWISE...THE PAYA AREA SHOULD SEE PRECIP DIMINISH EARLY THIS
EVENING AS FLOW TURNS OFFSHORE. THEN...AFTER COLD FRONT SWINGS
THROUGH THE AREA...PRECIP WILL BECOME SHOWERY AREA WIDE AND BECOME
MAINLY SNOW SHOWERS BY EARLY AFTERNOON FOR ALL BUT THE SRN AREA.
EVEN THERE...SOME MIXED PRECIP SHOULD OCCUR BY LATE AFTERNOON.

.LONG TERM...MODEL AGREEMENT IN THE MID TO LONG RANGE TOOK A
DETOUR TODAY AS THEY TOOK THE SHOTGUN APPROACH TO THE LOW MOVING
INTO THE WESTERN GULF AT 72 HOURS WITH THE MAIN FILES. THE LOW
SPREAD IS FROM YAKUTAT TO KETCHIKAN. AFTER THAT MODEL CONFIDENCE
IS IN THE LOW CATEGORY DUE TO WIDE VARIETY OF SOLUTIONS. TRIED TO
MAKE AS MINIMAL CHANGES AS POSSIBLE IN THE MID RANGE DUE TO
DIFFERENCES BUT THINK SOME CHANGES MAY HAVE BEEN BIGGER.

FOUND THE BEST CONSENSUS IN THE ECMWF/CANADIAN GEM/AND UKMET FOR
THE TRACK OF THE LOW WEDNESDAY TO THURSDAY. GRID MODIFICATIONS
WERE ADJUSTED TO THE ECMWF SOLUTION.

SO EXPECTING A WEAK TROUGH TO DISSIPATE ALONG THE COAST ON EARLY
THURSDAY. THERE SHOULD BE A BUILDING RIDGE OVER THE GULF A
SHORTWAVE DIGS SOUTHWARD IN THE UPPER TROUGH SOUTH OF THE EASTERN
ALEUTIANS FRIDAY NIGHT THAT WILL MOVE A DEVELOPING SYSTEM INTO THE
NORTHERN GULF FOR THE EARLY PART OF THE WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM AKST TUESDAY FOR
     AKZ026.
         HIGH WIND WARNING FROM MIDNIGHT TONIGHT TO 6 AM AKST TUESDAY FOR
     AKZ027-028.
         WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM AKST
     TUESDAY FOR AKZ025.
         WINTER STORM WARNING FROM 9 PM THIS EVENING TO 9 AM AKST TUESDAY
     FOR AKZ021-022.
         WIND ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM AKST TUESDAY FOR
     AKZ023.
         WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 9 AM AKST TUESDAY
     FOR AKZ019-020.
         WIND ADVISORY FROM 9 PM THIS EVENING TO 9 AM AKST TUESDAY FOR
     AKZ029.
         WIND ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR AKZ018.
MARINE...GALE WARNING FOR PKZ033-035-036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-022-031-032-034-043-051-
     052.

&&

RWT/BEZENEK