966
FXAK67 PAJK 261451
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
551 AM AKST THU NOV 26 2009
SHORT TERM
A WEAK RIDGE OVER THE EASTERN GULF OF ALASKA IS
PUSHING THE REMAINS OF THE THE MOISTURE FROM THE LOW THAT MOVED
INLAND OVERNIGHT. OPEN CELLED SHOWERS ARE VISIBLE IN THE
SATELLITE IMAGERY. A FAIR WEST WIND IS OCCURRING OVER MOST OF THE
COASTAL WATERS FROM CROSS SOUND AND SOUTH. THE SOUTHERLY PUSH OF
WINDS THROUGH THE INNER CHANNELS HAS REACHED THE NORTHERN LYNN
CANAL AREA AS SKAGWAY HAS STARTED GUSTING TO 40 MPH...WHICH GOES
ALONG WITH THE WIND ADVISORY THAT IS OUT FOR THE SKAGWAY AREA
THROUGH LATE AFTERNOON. THE WINDS SHOULD START TO DIMINISH AFTER
NOON.
FURTHER TO THE WEST A WAVE FROM THE PACIFIC THAT IS RUNNING
NORTHWARD ON THE CURRENT WEAKENING FRONT WILL DEVELOP A LOW AND
MOVE TO BE NORTHEAST OF KODIAK ISLAND BY AFTERNOON. A WARM FRONT
WITH THE LOW WILL START TO SPREAD RAIN ONSHORE THE NORTHEAST GULF
COAST AND NORTHERN PANHANDLE LATE THIS AFTERNOON AND THIS
EVENING. THE SOUTH WINDS AHEAD OF THE COLD FRONT LOOK LIKE THEY
WILL BE IN THE 35 TO 40 KT RANGE FOR GALES FOR THE OFF SHORE AND
INTO THE OUTER COASTAL WATERS OF THE PANHANDLE. EXPECT THAT THE
COLD FRONT WILL BEGIN TO IMPACT THE NORTHEAST GULF COAST LATE
TONIGHT AND LIE ALONG THE COAST OF THE PANHANDLE BY EARLY FRIDAY
MORNING.
GRID MODIFICATIONS THIS MORNING WERE DONE WITH A COMBINATION OF
THE NAM12 AND GFS40 BLEND... HOWEVER WHAT WAS IN THE FORECAST WAS
CLOSE SO ONLY MINOR ADJUSTMENTS WERE BEING MADE. CONFIDENCE IN
THE SHORT TERM IS ABOVE AVERAGE.
LONG TERM
BEGINS AS 982 MB LOW MAKES LANDFALL NEAR PWS WITH
OCCLUDED FRONT STRETCHING FROM THE LOW ALONG THE NORTHERN COAST
AND THROUGH THE PANHANDLE. LIKELY TO CATEGORICAL POPS ON TAP FOR
THE ENTIRE PANHANDLE AS FRONT MOVES THROUGH. 6 HR QPF RATES AROUND
ONE QUARTER OF AN INCH. SNOW LEVELS AROUND 2000 FEET IN THE
SOUTHERN ZONES DOWN TO AROUND 600 FT IN THE NORTHERN ZONES WITH
PASSES STILL RECEIVING SOME SNOW BUT MIXING WITH RAIN ON HAINES
BORDER. ONLY MINOR SNOW ACCUMULATIONS EXPECTED AT SEA LEVEL
LOCATIONS. WINDS WILL BE GUSTY WITH GALES HOISTED FOR OUTSIDE
WATERS AND NORTHERN LYNN CANAL WHILE SCA FOR MOST OF THE INNER
CHANNELS. SYSTEM CONTINUES TO MOVE NORTHEAST INTO CANADA WHILE
ONSHORE FLOW SETS UP AFTER THE FRONT MOVES THROUGH WITH LIKELY
POPS FOR SHOWERS. BRIEF RIDGE BUILDS IN ACROSS THE GULF FRIDAY
NIGHT THEN ATTENTION TURNS TO MAX GALE TO STORM FORCE LOW ENTERING
THE SOUTHWEST GULF ON SATURDAY.
MAX GALES DEVELOP THROUGH THE DAY ON SATURDAY AS A 967 MB LOW ON
THE ECMWF MOVES NORTH TO NORTHEAST INTO THE CENTRAL GULF TO BE
LOCATED JUST WEST OF MZ 310 BY 00Z SUNDAY. 00Z GFS AND 00Z
NAM12 BOTH HAVE DEEPER SOLUTIONS 958 MB AND 960 MB RESPECTIVELY
AND BOTH HAVE THE TRACK OF THE LOW SLIGHTLY FURTHER WEST. BARRIER
JET INDICATES STORM FORCE WINDS MAY BE REACHED IN WESTERN PARTS
OF MZ 52 LATE SATURDAY INTO SUNDAY MORNING. MODEL GUIDANCE
INDICATES THAT THICKNESS VALUES WILL NOT SUPPORT SNOW EXCEPT FOR
NORTHERN MOST ZONES AT PRECIP ONSET BUT QUICKLY TRANSITIONS TO AN
ALL RAIN EVENT FOR THE PANHANDLE ON SATURDAY. SNOW LEVELS RISE
BRIEFLY TO NEARLY 5KT IN THE SOUTHERN ZONES AND 1KFT TO 2KFT IN
THE NORTHERN ZONES AND 6HR QPF RATES APPROACHING ONE QUARTER OF
AN INCH COULD SEE SOME ENHANCED RUN OFF.
OF GREATER CONCERN IS LONG FETCH SOUTHWEST SWELL THAT WILL
ACCOMPANY THIS STORM. SWELL GUIDANCE IS INDICATING SOUTHWEST
SWELLS TO NEARLY 30 FT. WAVE MODEL GENERATED WAVE HEIGHTS OVER
40 FT IN THE CENTRAL AND EASTERN GULF SUNDAY. THIS SITUATION
SHOULD WATCHED CLOSELY.
BLENDED INHERITED GRIDS FROM HAND OFF WITH SHORT TERM DESK
THROUGH DAY 3 WITH 00Z ECMWF AS IT CONTINUES TO DISPLAY DECENT
RUN TO RUN CONSISTENCY. MODEL SPREAD ON TRACK ON STRENGTH
CONTINUES ON THE WEEKEND STORM...OPTED TO MAKE ONLY MINOR UPDATES
TO HEAVILY WEIGHTED HPC GUIDANCE IN THE OFFICIAL GRIDS WITH
LATEST ECMWF FOR DAY 4 THROUGH THE END OF THE PERIOD. FORECAST
CONFIDENCE IS AVERAGE TROUGH DAY THREE BUT FALLS TO BELOW AVERAGE
AFTER THAT POINT.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND ADVISORY UNTIL 6 PM AKST THIS EVENING FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-041>043-052.
SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031>036-051.
BEZENEK/CCC
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