FXAK67 PAJK 282313
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
213 PM AKST SAT NOV 28 2009

.SHORT TERM...THE 21Z SATELLITE SHOWS A WELL DEVELOPED GALE
FORCE SURFACE LOW NEAR BUOY 46001 SOUTHWEST OF KODIAK. WHILE THE
FIRST MID LEVEL FRONTAL BAND HAS MOVED ACROSS THE MAJORITY OF THE
PANHANDLE ALREADY LATE THIS MORNING...A STRONG SECOND WRAP OF
WINDS IS DEVELOPING IN PKZ0310 AND THESE STRONG 850 MB LLJ WINDS
WILL MOVE ACROSS THE EASTERN GULF AND PANHANDLE THIS EVENING AND
OVERNIGHT. THE GALE FORCE LOW AND WINDS ASSOCIATED WITH IT WILL
BE THE MAIN FORECAST PROBLEM THROUGH THE SHORT TERM PERIOD.
BLENDED INHERITED GRIDS TOWARD A 12Z GFS SOLUTION AS IT
INITIALIZED THE MID LEVEL VORTICITY THE BEST AND ITS TIMING ON
THE MOVEMENT OF THE SURFACE LOW WAS IN LINE WITH
OBSERVATIONS...WHILE THE 12Z NAM WAS TOO SLOW. FORECAST
CONFIDENCE IS ABOVE AVERAGE THROUGH THE SHORT TERM. 

 FOR TONIGHT WILL KEEP WIND ADVY OUT FOR AKZ022 AND AKZ023 AS THE
SECOND WRAP SHOULD BRING SOME VERY STRONG SOUTHWESTERLY WINDS
ALONG THE OUTER COAST. WITH POSITION AND MOVEMENT OF THE SURFACE
LOW AND WITH CURRENT OBSERVATIONS WILL LEAVE THE SOUTHERN
PANHANDLE OUT OF THE WIND ADVY...BUT ADDED AKZ017 AS THE SURFACE
LOW PASSES JUST WEST OF YAKUTAT BY 12Z TONIGHT AND THIS WILL
BRING THE BARRIER JET WINDS ONSHORE. PERIODS OF RAIN WILL
CONTINUE TO MOVE NORTHWARD ACROSS THE PANHANDLE TONIGHT...BUT THE
HEAVIEST RAINFALL WILL BE NEAR YAKUTAT WITH THE INCREASED SURFACE
CONVERGENCE AND BETTER MID LEVEL PVA. SNOW WILL MIX WITH RAIN
ACROSS THE NORTHERN PANHANDLE THIS EVENING BEFORE CHANGING OVER
TO ALL RAIN AT THE SURFACE AS THE SOUTHERLY PRESSURE GRADIENT
WILL RAPIDLY INCREASE THROUGH THE NIGHT...WITH SOUTHWESTERLY
850 MB WINDS INCREASING TO 50 KNOTS JUST WEST OF BARANOF ISLAND.
COULD SEE UP TO 3 INCHES OF SNOWFALL ALONG THE HAINES AND
KLONDIKE HIGHWAYS BEFORE THE SNOW CHANGES TO RAIN...BUT THE
OVERRUNNING VALUES FOR SNOWFALL HAVE DECREASED FROM PREVIOUS
MODEL RUNS. WITH A LARGE TRAPPED FETCH DEVELOPING ON THE
SOUTHEAST SIDE OF THE GALE FORCE LOW WILL SEE WAVE HEIGHTS
INCREASE TO NEAR 35 FEET IN THE COASTAL WATERS TONIGHT...BUT ONCE
THE SURFACE LOW JUMPS INLAND TOMORROW THE SOUTHWESTERLY SWELL
WILL GRADUALLY DIMINISH. 

 FOR TOMORROW THE GALE FORCE LOW WILL ADVECT INTO THE YUKON
RAPIDLY INCREASING THE SOUTHERLY SURFACE PRESSURE GRADIENT ACROSS
THE NORTHERN PANHANDLE WITH WEAK SURFACE RIDGING DEVELOPING IN
THE EASTERN GULF. EXPECT WIND ADVY GUSTS NEAR SKAGWAY THROUGHOUT
THE DAY TOMORROW WITH GALES IN NORTHERN LYNN CANAL AND CROSS
SOUND. ELSEWHERE WINDS WILL REMAIN LOCALLY BREEZY ACROSS THE
CENTRAL PANHANDLE IN NORTH-SOUTH ORIENTED CHANNELS. THE
PRECIPITATION WILL GRADUALLY BECOME MORE CONVECTIVE THROUGHOUT
THE DAY TOMORROW WITH CAA FROM 500 MB TO SURFACE ADVECTING
EASTWARD ACROSS THE CENTRAL GULF AND TOWARD THE PANHANDLE. THE
HEAVIEST RAINFALL AMOUNTS TOMORROW WILL BE ACROSS THE EASTERN
INNER CHANNELS WHERE THE MOUNTAINOUS TERRAIN ENHANCES CONVERGENCE
AND RAINFALL RATES. SNOW LEVELS WILL BE NEAR 1500 FEET ACROSS THE
PANHANDLE AS THE SOUTHWESTERLY FLOW ALOFT CONTINUES AND DON'T
EXPECT THE BEST MID LEVEL TO SURFACE CAA TO ADVECT ACROSS THE
PANHANDLE UNTIL AFTER HAND OFF. THE ATMOSPHERE DOES BECOME QUITE
UNSTABLE OFFSHORE TOMORROW AFTERNOON WITH LI VALUES NEAR -1 AND
CAPE VALUES ABOVE 100 J/KG SO ADDED ISOLATED THUNDERSTORMS ALONG
THE COASTAL WATERS. 

.LONG TERM...MODELS IN GOOD AGREEMENT UNTIL ABOUT MIDWEEK...WHEN
PROBLEMS DEVELOP. THE MAIN ISSUE IS THE WAY THEY DEVELOP A SYSTEM
COMING OFF ASIA INTO THE CENTRAL PAC...WITH THE 12Z GFS/UKMET MORE
AGGRESSIVE IN DEVELOPING A FAIRLY LARGE STORM...WHILE 00Z ECMWF
SHOWED LITTLE IN THE WAY OF DEVELOPMENT. THE 12Z ECMWF IS NOW MORE
IN LINE WITH THE OTHERS BY SHOWING DEVELOPMENT...BUT IT MOVES THE
LOW NWD MUCH MORE QUICKLY. NEEDLESS TO SAY...THE ECMWF IS HAVING
PROBLEMS HERE. THE GFS IS WELL SUPPORTED BY THE ENSEMBLES ALTHOUGH
THEY SUGGEST A LITTLE SLOWER MOVEMENT TO THIS LOW...WHICH HAS
RAMIFICATIONS ON HOW FAR W RIDGE DEVELOPS DOWNSTREAM OVER OUR
AREA. HPC PREFERRED GFS OVERALL. AFTER COORD WITH PAFC...DECIDED
TO GO WITH THE 12Z GFS FOR SUN NIGHT TO TUE...A BLEND OF GFS/NEW
HPC TUE NIGHT...THEN ALL NEW HPC FOR WED ONWARD.

LOW IMPACTING SHORT TERM PERIOD WILL BE MOVING NE OF THE AREA SUN
NIGHT. COLD ADVECTION WILL INCREASE OVER THE INNER CHANNELS SO
EXPECT PRECIP TO BE SHOWERY...AND WILL SEE PRECIP BECOME MIXED OR
ALL SNOW SHOWERS LATER SUN NIGHT AS 850 TEMPS DROP IN THE -8 TO
-10C RANGE OVER THE NRN AND CENTRAL AREAS. NOT AS CONFIDENT ABOUT
TSTMS AS IT LOOKS LIKE THE MID-LEVEL LAPSE RATES WILL NOT BE AS
LARGE HERE AS THEY ARE NOW IN THE HEAVIER CONVECTION NOW S OF THE
AKPEN. THE ADVY LEVEL WINDS AROUND PAGY SHOULD DECREASE BY
OVERNIGHT SUN NIGHT. WILL KEEP ADVY GOING TO 06Z MON.

NEXT SYSTEM WILL BE A SLOW MOVING OCCLUDED FRONT THAT WILL REACH
THE CENTRAL GULF TUE...THEN THE ERN GULF BY TUE NIGHT. THE FRONT
MAY STALL FOR A BIT AS MODELS INDICATE A LOW PRESSURE WAVE MOVING
NNE ALONG IT THRU THE ERN GULF LATE TUE INTO EARLY WED. THE FRONT
SHOULD SLOWLY PUSH INLAND WED AFTERNOON OR WED EVENING. COULD BE
SOME DECENT RAINFALL FROM THIS...WITH SOME SNOW POSSIBLE ON FRONT
END OF PRECIP OVER THE NRN AREA TUE NIGHT. WILL SEE STRONGER WINDS
AS WELL ESPECIALLY ALONG OUTER COAST AND ERN GULF...INCLUDING PAYA
AS PRES GRADIENT ORIENTATION IS FCST TO BE FAVORABLE FOR STRONG SE
WINDS THERE.

ONCE THIS FRONT MOVES E OF THE AREA...DEEP LAYER RIDGING SHOULD
BUILD OVER THE GULF FOR LATE WEEK...AND IT IS LOOKING MORE LIKELY
FOR A DRIER PERIOD THU INTO NEXT WEEKEND. THE DIFFERING RIDGE
POSITIONS AMONGST THE MODELS MAKE IT DIFFICULT TO GO COMPLETELY
DRY HOWEVER...AND TEMPS MAY BE TRICKY AS WELL. SHOULD BE AT LEAST
A LITTLE COOLER LATE NEXT WEEK BUT IF THE 12Z ECMWF IS CORRECT IN
PLACING UPPER RIDGE FURTHER W...A SOMEWHAT COLDER AIRMASS COULD
MOVE IN TOWARD NEXT WEEKEND FROM THE N.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 5 AM AKST SUNDAY FOR AKZ022-023.
         WIND ADVISORY FROM MIDNIGHT TONIGHT TO 9 PM AKST SUNDAY FOR 
     AKZ018.
         WIND ADVISORY FROM 9 PM THIS EVENING TO NOON AKST SUNDAY FOR 
     AKZ017.
MARINE...GALE WARNING FOR PKZ012-022-042-043-051-052. 
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-031>036-041. 

&&

$$

PSS/RWT