Gale Warning 385, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
130 PM AKST WED NOV 25 2009

.SHORT TERM...A 980 MB GALE FORCE LOW 150 NM SOUTHWEST OF SITKA
CONTINUES TO WEAKEN AS IT ADVECTS NORTHWARD EARLY THIS AFTERNOON.
A STRONG 850 MB LLJ CONTINUES TO ADVECT OVER THE PANHANDLE
BRINGING LOCALLY WINDY CONDITIONS...ESPECIALLY ALONG THE SOUTHERN
OUTER COAST WITH GUSTS TO 45 MPH. ELSEWHERE...LOCALLY HEAVY SNOW
CONTINUES ALONG THE HAINES HIGHWAY AND WITH CONTINUED UPSLOPE
FLOW THROUGH TONIGHT EXPECT ANOTHER 6 TO 10 INCHES. THE
DISSIPATION OF THE GALE FORCE LOW IN THE NORTHERN GULF TONIGHT
AND THE BUILDING SURFACE RIDGE ACROSS THE PANHANDLE TOMORROW ARE
THE MAIN FORECAST PROBLEMS THROUGH THE SHORT TERM AND BOTH THE
12Z NAM AND GFS HAVE INITIALIZED THE MID LEVEL VORTICITY AND
MOISTURE FIELDS WELL. SO BLENDED THE 12Z GFS AND NAM THROUGH THE
SHORT PERIOD THOUGH USED MORE OF A NAM SURFACE WIND FIELD BECAUSE
IT HAD A MORE REALISTIC SURFACE PRESSURE GRADIENT ACROSS THE
NORTHERN PANHANDLE WITH THE BUILDING SURFACE RIDGE TOMORROW.
FORECAST CONFIDENCE IS HIGH THROUGH THE SHORT TERM PERIOD.

 FOR TONIGHT WILL CONTINUE TO SEE WINDY CONDITIONS ALONG THE
OUTER COAST THROUGH MIDNIGHT WITH A SECOND WRAP OF STRONG 850 MB
WINDS ADVECTING NORTHWARD. LOCALLY WINDY CONDITIONS WILL ALSO
SPREAD NORTHWARD ALONG THE INNER CHANNELS THROUGH THE NIGHT AS
THE SECOND WRAP MOVES NORTHWARD AND A SURFACE RIDGE BUILDS INTO
THE SOUTHERN AND CENTRAL PANHANDLE. RAINFALL AMOUNTS WILL
CONTINUE TO BE HIGHEST ALONG THE OUTER COAST THROUGH TONIGHT AS
THE 500 MB LOW WILL ADVECT NORTHWARD AND MOVE ONSHORE JUST EAST
OF YAKUTAT BAY KEEPING THE BEST MID LEVEL PVA WEST OF CHATHAM
STRAIT. THE RAIN/SNOW LINE WILL REMAIN IN THE NORTHERN PANHANDLE
THROUGH TONIGHT...HOWEVER COULD SEE A FEW SNOWFLAKES MIX WITH
RAIN IN THE HEAVIER SHOWERS. STRONG UPSLOPE FLOW CONTINUES IN THE
HAINES AREA WITH THE OVERRUNNING SOUTHEASTERLY WINDS ALOFT AND
THIS WILL CONTINUE TO PRODUCE LOCALLY HEAVY SNOWFALL THROUGH
MIDNIGHT. BY LATE TONIGHT THE SURFACE PRESSURE GRADIENT WILL
BECOME SOUTHERLY THROUGHOUT THE PANHANDLE AND THIS WILL CAUSE
SNOW LEVELS TO RISE ABOVE 1000 FEET IN HAINES AND SKAGWAY.

 FOR TOMORROW MID LEVEL RIDGING WILL ADVECT ACROSS THE PANHANDLE
AND THIS WILL HELP TO BUILD A SURFACE RIDGE INTO THE EASTERN GULF
AND PANHANDLE. THE SOUTHERLY SURFACE PRESSURE GRADIENT WILL BE
QUITE STRONG ACROSS THE NORTHERN INNER CHANNELS AND EXPECT WIND
ADVY GUSTS NEAR TAIYA INLET WITH GALES IN NORTHERN LYNN CANAL.
WILL ALSO SEE LOCALLY WINDY NEAR CROSS SOUND IN THE MORNING WITH
A STRONG SOUTHWESTERLY PRESSURE GRADIENT THERE. SHOWERS WILL
CONTINUE TO ADVECT ACROSS THE PANHANDLE TOMORROW WITH
SOUTHWESTERLY ONSHORE FLOW THROUGH 500 MB...HOWEVER WITH THE MID
LEVEL RIDGING DONT EXPECT CONVECTION TO BE AS VIGOROUS TOMORROW.
THE HIGHEST RAINFALL AMOUNTS WILL REMAIN ALONG THE EASTERN INNER
CHANNELS TOMORROW WHERE THE TERRAIN ENHANCES THE RAINFALL...WHILE
THE OUTER COAST WILL SEE A FEW SUNNY BREAKS. WITH THE SOUTH TO
SOUTHWESTERLY FLOW AT ALL LEVELS ACROSS THE NORTHERN PANHANDLE
WILL SEE THE SNOW LEVEL REMAIN ABOVE 1500 FEET THROUGH TOMORROW
AFTERNOON.

&&

.LONG TERM...LONG TERM PERIOD STARTS WITH A RIDGE OVER THE
PANHANDLE QUICKLY TRACKING EAST AS AN UPPER LVL TROUGH TRACKS
INTO THE WESTERN GULF. WEAK 975 MB LOW TRACKS NORTHWARD OVER
KODIAK FRI. SAT INTO SUN A DEVELOPING 970 MB LOW MOVING FROM THE
N PAC INTO THE W GULF. MODELS HAVE BECOMING A BIT MORE CONSISTENT
WITH THE TRACK OF THIS LOW JUST EAST OF PAMD. AS THIS LOW MAKES
LANDFALL AND WEAKENS A SURFACE RIDGE DEVELOPS OVER THE S GULF
WITH A LOW DEVELOPING OVER THE BERING SEA. GALE FORCE WINDS ALONG
THE COASTAL WATERS WITH SUBSTANTIAL SEAS HEIGHTS...30 PLUS FEET
NOT OUT OF THE QUESTION SAT INTO SUN. PRECIP WILL BE A MIX OF
RAIN AND SNOW OVER THE NORTHERN PANHANDLE WITH MOSTLY RAIN TO THE
SOUTH. 850 TEMPS REMAINS ABOVE -6C THROUGH THE WEEKEND WITH A
BRIEF DROP TO ABOUT -10C MON. RAISED QPF AMOUNTS FOR THE WEEKEND
AS MOISTURE CONNECTION LOOKS TO BE WELL ESTABLISHED.

MODELS WERE IS GOOD AGREEMENT AT THE START OF THE LONG TERM
THROUGH ABOUT DAY 5 BEFORE DIVERGING FOR THE REMAINDER OF THE
LONG TERM. USED A BLEND OF GFS WITH NAM12 UNTIL DAY
4...TRANSITIONING FROM THE SHORT TERM. HPC GUIDANCE WAS A GOOD
COMPROMISE BETWEEN THE GFS AND EC...WHICH WERE IN GOOD AGREEMENT
WITH THE STRENGTH OF THE NEXT LOW BUT A BIT OFF IN FINAL TRACK.

FORECAST CONFIDENCE WAS AVERAGE TO A BIT ABOVE AVERAGE FOR THE
START OF THE LONG TERM WITH GOOD MODEL CONSTANCY AND AGREEMENT
BETWEEN MODELS. CONFIDENCE DROPS AS MODELS DIVERGE TOWARD THE END
OF THE PERIOD.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR
AKZ023-027.
         WINTER STORM WARNING UNTIL MIDNIGHT AKST TONIGHT FOR
AKZ019.
         WIND ADVISORY FROM 3 AM TO 6 PM AKST THURSDAY FOR
AKZ018.
         WIND ADVISORY UNTIL 6 PM AKST THIS EVENING FOR AKZ028.
MARINE...GALE WARNING FOR PKZ012-041>043.
         SMALL CRAFT ADVISORY FOR
PKZ011-013-021-022-031>036-051-052.

&&

PSS/PRB