Gale Warning 287, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1233 PM AKDT SAT OCT 25 2008

.SHORT TERM...A DEEPENING GALE FORCE LOW IN THE NORTHERN PACIFIC
CONTINUES TO ADVECT NORTHEASTWARD THIS MORNING. A VERY IMPRESSIVE
DRY SLOT IS VISIBLE ON SATELLITE IMAGERY INDICATING THAT THE GALE
FORCE LOW WILL CONTINUE TO STRENGTHEN INTO THIS AFTERNOON AND
EVENING. ISOLATED SNOW SHOWERS WILL CONTINUE TO DIMINISH INTO THE
AFTERNOON ACROSS THE CENTRAL AND SOUTHERN PANHANDLE AS A MID
LEVEL RIDGE ADVECTS OVER THE PANHANDLE AHEAD OF THE GALE FORCE
LOW. ACROSS THE NORTHERN PANHANDLE SKIES WILL REMAIN MOSTLY SUNNY
THROUGH THE AFTERNOON WITH NORTHERLY WINDS REMAINING BELOW
15 KNOTS. WINDS AND SEAS ALONG THE COASTAL WATERS WILL CONTINUE
TO DIMINISH INTO THE AFTERNOON AS THE SURFACE PRESSURE GRADIENT
CONTINUES TO RELAX. WENT WITH A BLEND OF THE 12Z NAM/GFS FOR
TODAYS PACKAGE AS THE MODEL DIFFERENCES WERE SMALL THROUGH
TOMORROW AFTERNOON. THE 12Z GFS DID HINT AT THE DEVELOPMENT OF A
TRIPLE POINT SURFACE LOW IN THE SOUTHEASTERN GULF BY TOMORROW
AFTERNOON AND BELIEVE THIS TO BE REALISTIC...SO ADJUSTED THE WIND
FIELD TO ACCOUNT FOR THE WEAK TRIPLE POINT DEVELOPMENT.

 FOR TONIGHT THE GALE FORCE LOW WILL ADVECT INTO THE WESTERN GULF
WITH THE ASSOCIATED FRONT PUSHING INTO THE EASTERN GULF BY LATE
TONIGHT. WITH THE SURFACE PRESSURE GRADIENT ORIENTATION, BARRIER
JET DEVELOPMENT, AND 850 MB LLJ TO 65 KNOTS WILL SEE WINDS
REACHING STORM FORCE IN THE NORTHERN GULF...WITH GALES IN
EASTERLY OUTFLOW AREAS WITHIN THE INNER CHANNELS. EXPECT WIND
ADVY GUSTS ALONG THE OUTER COASTAL WATERS AS THE 850 MB LLJ AND
FRONTAL BAND ADVECT NORTHEASTWARD INTO THE WESTERN PANHANDLE BY
LATE TONIGHT. ATTM SURFACE PRESSURE GRADIENT ORIENTATION IS NOT
FAVORABLE FOR WIND ADVY GUSTS ALONG THE CENTRAL INNER CHANNELS SO
WILL KEEP THOSE AREAS LOCALLY WINDY INTO TOMORROW MORNING. WITH
FRONTAL BAND ADVECTING NORTHEASTWARD INTO THE WESTERN PANHANDLE
BY LATE TONIGHT WILL SEE RAIN BEGINNING. HOWEVER WITH THE
SOUTHEASTERLY TO EASTERLY DRY MID LEVEL WIND TRAJECTORIES WILL
SEE PRECIP STARTING A LITTLE LATER ACROSS THE SOUTHERN AND
CENTRAL PANHANDLE.

 FOR TOMORROW EXPECTING THE WIND ADVY GUSTS TO CONTINUE INTO THE
EARLY AFTERNOON ALONG THE COASTAL WATERS AND NEAR HYDABURG AS THE
850 MB LLJ ADVECTS EASTWARD AND SLOWLY DIMINISHES INTO THE
AFTERNOON. GALES WILL CONTINUE IN THE NORTHERN GULF AS THE
SURFACE PRESSURE GRADIENT WILL CONTINUE TO REMAIN STRONG THERE.
ALONG THE INNER CHANNELS TOMORROW WINDS WILL BEGIN AS NORTHERLY
BUT WILL QUICKLY CHANGE TO SOUTHERLY AS THE FRONT AND ASSOCIATED
850 MB LLJ ADVECT NORTHWARD ACROSS THE PANHANDLE. CONCERNED
CENTRAL PANHANDLE COULD SEE WIND ADVY GUSTS TOMORROW BUT WITH THE
FRONTAL BAND BEING SHEARED APART BY THE MOUNTAINS AND MOST OF THE
UPPER LEVEL SUPPORT IN THE WESTERN GULF...WILL KEEP AREA LOCALLY
WINDY ATTM. PERIODS OF RAIN WILL CONTINUE TO MOVE NORTHWARD
ACROSS THE PANHANDLE TOMORROW AND WITH 850 MB TEMPERATURES RISING
THROUGH THE EARLY MORNING SHOULD SEE HIGH TEMPS REACH INTO THE
LOW TO MID 40S. WITH 850 MB TEMPERATURES FROM -8 TO -10 C ICY
STRAIT NORTHWARD IN THE EARLY MORNING...PRECIP COULD START OUT AS
A LITTLE SNOW, BUT THIS WILL CHANGE INTO RAIN BY MID MORNING AS
WARMER SOUTHERLY FLOW WILL DOMINATE. HOWEVER IN THE NORTHERN
PANHANDLE NEAR THE PASSES WILL HAVE TO WATCH TO SEE IF SNOWFALL
AMOUNTS REACH ADVY LEVEL AS OVERRUNNING SCENARIO IS
FAVORABLE...ESPECIALLY IF COLD AIR REMAINS LONGER THAN THE 12Z
MODELS INDICATE.

.LONG TERM...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF BEGIN
TO MANIFEST BY TUESDAY MORNING AND SO DO NOT PLAN ON ANY MAJOR
CHANGES...IF ANY AT ALL...TO CURRENT GRIDS BEYOND TUESDAY NOON.
PRIOR TO TUESDAY MORNING...MUCH BETTER MODEL AGREEMENT ON THE
TRACK AND INTENSITY OF THE DEEPENING GALE REFERENCED IN THE SHORT
TERM DISCUSSION. MODELS WEAKEN THIS FEATURE OFFSHORE SOMEWHERE
BETWEEN YAKUTAT BAY AND PRINCE WILLIAM SOUND. PARTICULARLY GOOD
AGREEMENT BETWEEN EC AND UKMET THROUGH THE END OF THE UKMET MODEL
RUN. WITH THIS IN MIND...BLENDED GRIDS WITH A STRONG BIAS FOR THE
EC AND UKMET THROUGH TUESDAY MORNING AND THEN INTERPOLATED TO
EXISTING GRIDS THEREAFTER. THIS HAD THE EFFECT OF MAINTAINING THE
STRONG NORTHERLY PRESSURE GRADIENT OVER THE NORTHERN INNER
CHANNELS THROUGH WEDNESDAY WHILE DOWNPLAYING THE OUTLIER LOW IN
GFS THAT ENTERS THE SOUTHEAST GULF ON TUESDAY MORNING.

PUSHED THE RAIN-SNOW LINE A LITTLE FARTHER NORTH SUNDAY NIGHT AND
SO BELIEVE THAT ONLY THE FAR NORTHERN INNER CHANNELS - SKAGWAY
AND THE HIGHWAYS PLUS YAKUTAT WILL SEE STRAIGHT SNOW SUNDAY
NIGHT.

A SYSTEM ENTERING THE WESTERN GULF ON WEDNESDAY IS BEING HANDLED
VERY DIFFERENTLY BY GFS AND ECMWF...BUT NEITHER SOLUTION BEGINS
TO AFFECT THE PANHANDLE UNTIL FRIDAY AT THE EARLIEST. BY THIS
TIME THE MODELS ARE IN BETTER AGREEMENT WITH THE LOW WEST OF
VANCOUVER ISLAND AND TRACKING NORTHWEST INTO THE CENTRAL GULF.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING FOR PKZ042-043-051-052.
         GALE WARNING FOR PKZ021-022-033-041.
         SMALL CRAFT ADVISORY FOR PKZ011-013-034>036.

&&

PSS/FRITSCH