High Wind in Alaska, February 5, 2010

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
556 AM AKST FRI FEB 5 2010

.SHORT TERM...THE 13Z SATELLITE REVEALS A WELL DEFINED AND
STRENGTHENING TRIPLE POINT LOW 50 NM WEST OF THE CHARLOTTES WITH
ITS ASSOCIATED PARENT LOW NEAR 50N 140W. THIS TRIPLE POINT LOW
AND THE WINDY CONDITIONS ASSOCIATED WITH IT ARE THE MAIN FORECAST
PROBLEM THROUGH THE SHORT TERM PERIOD. VERY WINDY CONDITIONS HAVE
ALREADY BEEN REPORTED ALONG THE CHARLOTTES WITH SEVERAL BUOYS AND
OBSERVATION SITES REPORTING GUSTS GREATER THAN 60 KNOTS AND THESE
WINDY CONDITIONS WILL MOVE UP ALONG THE OUTER COAST OF THE
PANHANDLE TODAY. USED A BLEND OF THE 06Z NAM AND LOCAL WRF MODEL
FOR THE SHORT TERM FORECAST PACKAGE TODAY AS BOTH THESE MODELS
INITIALIZED AND HANDLED THE TRIPLE POINT LOW AND RESULTANT
SURFACE PRESSURE GRADIENT THE BEST. KEPT WIND WARNING AND WIND
ADVY TIMES THE SAME AS THE CORE OF THE 70 KNOT LLJ 850 MB WINDS
WILL REMAIN ALONG THE OUTER COAST AND IN THE EASTERN GULF THROUGH
THIS EVENING. FORECAST CONFIDENCE IS ABOVE AVERAGE IN THE SHORT
TERM.

 FOR TODAY WINDY CONDITIONS WILL CONTINUE TO SPREAD NORTHWARD
ACROSS THE PANHANDLE THROUGH THE DAY REACHING THE ICY STRAIT
CORRIDOR BY THE AFTERNOON. THE STRONGEST 850 MB LLJ WINDS DO
REMAIN ALONG THE OUTER COAST AS THE TRIPLE POINT LOW ADVECTS
NORTHWESTWARD AND FOR THIS REASON DIDN'T ADD WIND ADVY TO MOST
AREAS IN THE CENTRAL PANHANDLE. HOWEVER...IF THE PRESSURE RISES
BEHIND THE FRONTAL BOUNDARY ARE STRONGER THAN FORECAST COULD SEE
ADVY GUSTS AS FAR NORTH AS JUNEAU BY AFTERNOON. BELIEVE WINDS
WILL GUSTS TO STORM FORCE ALONG THE OUTER COAST AS THE CORE OF
THE LLJ WINDS ADVECTS OVERHEAD. AS FAR AS PRECIP CONCERNS...THE
SOUTHEASTERLY MID LEVEL WIND TRAJECTORY WILL CONTINUE TO LIMIT
PRECIP AMOUNTS THROUGH THE AFTERNOON WITH THE BULK OF THE PRECIP
REMAINING ALONG THE OUTER COAST. THE BIORKA RADAR THIS MORNING
SHOWS STRONG EVIDENCE OF THE DOWNSLOPING EASTERLY COMPONENT WITH
BANDS OF RAINFALL FALLING APART AS THEY ADVECT NORTHWESTWARD PAST
BARANOF ISLAND. 850 MB TEMPS HAVE WARMED TO NEAR -1 C AS FAR
NORTH AS THE ICY STRAIT CORRIDOR AND SO ANY BRIEF SNOWFLAKES THIS
MORNING ACROSS THE CENTRAL PANHANDLE WILL QUICKLY CHANGE TO RAIN
AS THE STRONG MID AND LOW LEVEL WINDS MIX WARM AIR ADIABATICALLY
TO THE SURFACE. PRECIP WILL HAVE A VERY HARD TIME MAKING IT AS
FAR NORTH AS PAHN AND PAGY AND SO DECREASED PRECIP AMOUNTS THERE
FOR TODAY AS SOUTHEASTERLY WINDS WILL REMAIN THE DOMINANT MID
LEVEL FLOW THROUGH THE AFTERNOON. COULD SEE SOME MINOR UPSLOPE
PRECIP OVER THE ARCTIC BOUNDARY NEAR HAINES THIS AFTERNOON...BUT
THE ARCTIC BOUNDARY REMAINS DIFFUSE AND WEAK ATTM WITH THE MID
LEVEL RIDGE IN THE NORTHERN PANHANDLE QUICKLY GIVING WAY TO THE
SHORTWAVE TROUGH MOVING INTO THE GULF.

 FOR TONIGHT WILL CONTINUE TO SEE WINDY CONDITIONS ALONG THE
OUTER COAST AND NORTHERN GULF AND WITH THE BARRIER ENHANCED FLOW
NEAR YAKUTAT WILL SEE STORM FORCE WIND GUSTS IN PKZ051 AND
PKZ052 THIS EVENING BEFORE THE TRIPLE POINT LOW ADVECTS INTO
PRINCE WILLIAM SOUND. A SECOND WRAP OF STRONG LLJ 850 MB WINDS
ADVECTS OVER THE SOUTHERN PANHANDLE TONIGHT AND SO WILL HAVE TO
MONITOR FOR EXTENSION OF THE CURRENT WIND ADVY IF THOSE STRONG
850 MB WINDS DO MIX TO THE SURFACE. AFTER THE ASSOCIATED FRONT
FROM THE TRIPLE POINT LOW ADVECTS THROUGH THE PANHANDLE BY THE
EVENING WILL CONTINUE TO SEE SCATTERED TO NUMEROUS SHOWERS ACROSS
THE PANHANDLE WITH WEAK CAA AT MID LEVELS. THE MID LEVEL TROUGH
AS A WHOLE BEGINS TO ADVECT TOWARD THE SOUTHERN PANHANDLE LATE
TONIGHT AND WITH THE INCREASED MID LEVEL PVA THIS WILL BRING THE
BEST CHANCE OF RAINFALL TO THE PRINCE OF WALES ISLAND AREA. THE
STRONG SOUTHERLY SURFACE PRESSURE GRADIENT WILL CONTINUE TO
ADVECT NORTHWARD THROUGH MOST THE PANHANDLE TONIGHT AND SO WILL
SEE SNOW LEVELS RISE TO ABOVE 1500 FEET EVEN IN THE SKAGWAY AREA
WITH LOCALLY BREEZY CONDITIONS OUT OF THE SOUTHWEST AND SOUTHERLY
SMCR ADVY IN THE LYNN CANAL AREA.

&&

.LONG TERM...THE MEDIUM RANGE MODELS SHOW A SIGNIFICANT
DISAGREEMENT WITH A LARGE SURFACE LOW IN THE GULF SLOWLY MOVING
NORTH INTO THE ALASKA INTERIOR SATURDAY AND SATURDAY NIGHT. THE
DIFFERENCES ARE AT ALL LEVELS WITH AN UPPER LOW IN THE WESTERN
ALASKA INTERACTS A BUILDING UPPER RIDGE TO THE NORTHEAST. NO ONE
PARTICULAR MODEL SHOWS A REASONABLE CONSISTENCY. BEGINNING EARLY
NEXT WEEK...MODELS SEEM TO MAKE A LITTLE BETTER AGREEMENT BUT
SPREAD AGAIN LATE MONDAY NIGHT THEN CONTINUE THROUGH THE WORKING
WEEK.

 THE MODEL DIFFERENCES BECOME WORSE BY MIDDLE OF THE WEEK FOR
INCREASING UNCERTAINTY. THE GFS PREFERS TO HOLD A SURFACE LOW IN
THE NORTHEASTERN PACIFIC WHILE THE ECMWF PUSHES THE LOW INTO THE
SOUTHEASTERN BERING. ALTHOUGH THE 00Z RUN ECMWF SHOWS A LITTLE
SLOWER PROGRESS...IT SHOWS A BIT BETTER CONSISTENCY THAN THE GFS
FROM THEIR PREVIOUS RUNS. BASED ON THE MODEL TENDENCY AND LOWER
THAN AVERAGE FORECAST CONFIDENCE...DECIDED NOT TO MAKE ANY
SIGNIFICANT CHANGES OVER THE INHERITED GRIDS. TO MAKE THE
TRANSITION SMOOTH FROM THE SHORT TERM FORECAST TO THE BEGINNING OF
THE LONG TERM...USED THE COMBINATION OF THE NAM AND ECMWF THEN
MADE TRANSITION TO A BLEND OF THE HPC GUIDANCE WITH THE ECMWF AS A
REFRESHING TOOL THROUGH THE END OF THE PERIOD.

 BEHIND THE TRAILING EDGE OF A FRONTAL BOUNDARY MOVING NORTH INTO
YUKON...LOCALLY BREEZY TO WINDY CONDITIONS WILL REMAIN ACROSS THE
NORTHERN AREAS SATURDAY INTO EARLY SATURDAY NIGHT WITH DECREASING
POPS TOWARDS THE EARLY NEXT WEEK. WINDS ACROSS THE OUTER COASTAL
WATERS WILL DROP BELOW THE GALE FORCE BUT THE SEAS WILL REMAIN
ROUGH. SMALL CRAFT WINDS ACROSS THE INNER CHANNELS SATURDAY WILL
SUBSIDE AS WELL BUT THE SEAS NEAR OCEAN ENTRANCES WILL REMAIN
ROUGH FOR A WHILE. TEMPERATURES REMAIN COLD ENOUGH FOR SNOW AND
RAIN MIX ACROSS THE NORTHERN AREAS WHILE SOUTHERN HALF OF THE
PANHANDLE WILL SEE ALL RAIN.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 8 AM THIS MORNING TO 4 PM AKST THIS
     AFTERNOON FOR AKZ027.
         WIND ADVISORY FROM 10 AM THIS MORNING TO 9 PM AKST THIS EVENING
     FOR AKZ023.
         WIND ADVISORY UNTIL NOON AKST TODAY FOR AKZ018.
         WIND ADVISORY UNTIL 9 PM AKST THIS EVENING FOR AKZ028.
MARINE...STORM WARNING FOR PKZ041>043-051-052.
         GALE WARNING FOR PKZ021-022-033-035-036.
         SMALL CRAFT ADVISORY FOR PKZ011>013-031-032-034.

&&

PSS/AHN