Small Craft Advisory 321, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
131 PM AKDT SUN MAY 1 2011

.SHORT TERM...993 MB LOW NEAR 52N/142W WILL DRIFT NNE LATE THIS
AFTERNOON AND TONIGHT...THEN TURN ENE AND WEAKEN AS IT MOVES INTO
THE FAR SERN GULF MON. OCCLUDED FRONT OVER THE SE GULF WILL MOVE
NNE THRU MUCH OF THE PANHANDLE TONIGHT...AND DISSIPATE OVER THE
FAR NRN AND ERN AREAS MON MORNING. ENDED UP USING THE 00Z ECMWF
AS IT REMAINS MOST CONSISTENT WITH THE TRACK OF THE LOW.

 MAIN FORECAST CONCERN WILL BE WINDS. LOOKS LIKE ADVY LEVEL WINDS
WILL BE OCCURRING OVER THE SRN AREA TONIGHT...AS THE OCCLUDED
FRONT MAKES SLOW EWD PROGRESS TOWARD THEM. THE FRONT WILL WEAKEN
ENOUGH OVER THE INNER CHANNELS FOR WINDS TO DROP OFF TOWARD
DAYBREAK BUT THE DROP WILL BE A SLOW ONE. HAVE DECIDED TO KEEP
THE WIND ADVYS FOR BOTH ZONES 27 AND 28 GOING UNTIL 5 AM MON.
WILL HAVE GALES FOR THE FAR SRN INNER CHANNELS AND SE GULF AREA
TONIGHT...AND SCA WINDS FOR PARTS OF THE CENTRAL AND REMAINING
SRN INNER CHANNEL AREA. THESE WINDS SHOULD DROP OFF SLOWLY LATER
TONIGHT AND MON.

 OTHERWISE RAIN OVER THE SRN HALF OF THE AREA SHOULD SPREAD TO
MOST OF THE NRN AREA TONIGHT. THE FAR NRN AREA INCLUDING PAYA
WILL HAVE LOWEST POPS AS FRONT WILL BE WEAKEST AS IT REACHES THEM
LATE TONIGHT...AND LOWER LEVEL FLOW WILL REMAIN SOMEWHAT ELY.
DEFINITELY EXPECT THE MOST RAINFALL OVER THE SRN HALF OF THE AREA
TONIGHT AND MON...WITH RAINFALL AMOUNTS OF 1 INCH OR MORE LIKELY
BY LATE MON AFTERNOON.

&&

.LONG TERM...MODELS ARE IN GENERAL AGREEMENT THROUGH THE MIDDLE OF
THIS WEEK WITH A WEAKENING UPPER LEVEL SHORTWAVE TROUGH MOVES
NORTHEAST AWAY FROM THE AREA TUESDAY MORNING AND A WEAK RIDGE
BUILDS ACROSS THE EASTERN GULF AND SOUTHEAST ALASKA THROUGH
WEDNESDAY MORNING. A WEAK SURFACE LOW ASSOCIATED WITH THE UPPER
TROUGH WILL REMAIN NEAR HAIDA GWAII...FORMERLY CHARLOTTES...EARLY
MONDAY NIGHT THEN DISSIPATE AS A RIDGE OF HIGH PRESSURE BUILDING
ACROSS THE FORECAST DOMAIN THROUGH WEDNESDAY MORNING. 50/50
BLENDING OF THE GFS AND NAM WAS USED THROUGH WEDNESDAY MORNING
TIME FRAME. MODEL SPREADS BECOME LARGER BEGINNING ON WEDNESDAY WITH
A DEVELOPING LOW IN THE SOUTHERN GULF DRIFTS NORTHEAST ACROSS THE
CENTRAL GULF THROUGH LATE THURSDAY THEN STALLS OR MOVES A LITTLE
TO THE EAST OVER THE WEEKEND AS IT BECOMES A BROAD AREA OF LOW
PRESSURE. USED THE HPC ENSEMBLE MEANS FROM WEDNESDAY NIGHT THROUGH
THE END.

 AN ACCEPTABLE MODEL CONSENSUS BETWEEN THE GFS AND NAM BRINGS THE
DEVELOPING LOW IN THE SOUTHERN GULF TO NEAR 55N/140W BY WEDNESDAY
NIGHT. THIS APPROACHING LOW WILL PUSH A WEAK FRONT INTO THE
EASTERN GULF AND TIGHTEN PRESSURE GRADIENT ALONG THE WESTERN EDGE
OF THE RIDGE ACROSS THE CENTRAL AND SOUTHERN AREAS. EXPECT 25 TO
30 KNOTS SOUTHERLY WINDS WITH ROUGH SEAS ACROSS THE OUTER COASTAL
WATERS AND OCEAN ENTRANCES TUESDAY NIGHT INTO WEDNESDAY. RAIN BAND
ASSOCIATED WITH THE WEAK LOW REMAINING NEAR HAIDA GWAII WILL
MAINTAIN LIKELY TO CATEGORICAL POPS ACROSS THE SOUTHERN AREAS
MONDAY NIGHT INTO TUESDAY MORNING. THE FRONT ASSOCIATED WITH THE
APPROACHING LOW WILL LIKELY TO ARRIVE EASTERN GULF AND PANHANDLE
COAST BY LATE TUESDAY NIGHT THEN SPREAD NORTHEAST ACROSS SOUTHEAST
ALASKA DURING THE DAY OF WEDNESDAY WITH LIKELY TO CATEGORICAL
POPS. LIKELY POPS WILL REMAIN OVER MAJORITY PARTS OF THE PANHANDLE
THROUGH THURSDAY NIGHT THEN SLIDE SOUTHEAST ACROSS THE SOUTHERN
AREAS THROUGH FRIDAY.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 5 AM AKDT MONDAY FOR AKZ027.
         WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 5 AM AKDT MONDAY FOR
     AKZ028.
MARINE...GALE WARNING FOR PKZ033-036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ021-022-034-035-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

&&

RWT/AHN