Storm Warning 40, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
311 PM AKST TUE DEC 9 2014

.SHORT TERM...NO REST FOR THE WEARY HERE IN SE AK AS ONE LOW EXITS
THE AREA TONIGHT AND ANOTHER HEADS TOWARD THE FAR SE GULF BY LATE
WED AFTERNOON. USED BLEND OF THE 12Z GEM AND ECMWF AS THEY WERE
HANDLING BOTH SYSTEMS NEARLY THE SAME.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL AND WINDS. RIGHT
NOW...RAIN COVERS MOST OF THE MAIN PART OF THE PANHANDLE WITH LOW
MOVING N THRU THE SE GULF. THE LOW WILL WEAKEN THEN DISSIPATE AS IT
REACHES THE NRN PANHANDLE LATE TONIGHT. THE PRECIP WILL BEGIN TO
DIMINISH SLOWLY FROM THE S TONIGHT...WITH THE NRN THIRD SEEING
PRECIP TAPER OFF LATE TONIGHT. HOWEVER...RAIN WILL SPREAD NWD INTO
THE FAR SRN AREA TOWARD DAYBREAK WED AS NEXT LOW APPROACHES THE
AREA FROM THE S. THINK THIS RAIN WILL REACH THE FREDERICK SOUND
AREA BY LATE MORNING TO EARLY AFTERNOON...ALTHOUGH THE PRECIP
SHIELD WILL ENCOUNTER INCREASING OFFSHORE FLOW SO PRECIP INTENSITY
WILL BE DIMINISHING AS IT HEADS NWD. THE PAYA AREA MAY SEE SPOTTY
RAIN TONIGHT...THEN SEE DRIER WEATHER WED AS OFFSHORE FLOW PICKS
UP. THE NRN THIRD TO HALF OF THE MAIN PART OF THE PANHANDLE WILL
ALSO LIKELY BE DRY FOR MUCH OF WED.

AS FOR WINDS...THEY WILL BE STRONGEST OVER THE SRN PANHANDLE FOR
THIS EVENING AS LOW PASSES NWD AND SECOND WRAP OF FRONT PASSES
THRU THEM. EXPECT GALE FORCE S-SELY WINDS OVER THE FAR SE GULF AND
FAR SRN INNER CHANNELS THIS EVENING...WITH STRONG WIND HEADLINES
NEEDED FOR PUBLIC ZONES 27 AND 28 THRU THE EVENING. THE LOW AND
SECOND WRAP WILL BE WEAKENING RAPIDLY THOUGH SO NOT EXPECTING
THESE WINDS TO BE NOT AS STRONG AS LOW/FRONTAL REMNANT PASS BY.
MAY GET SHORT PERIOD OF SCA WINDS OVER THE CENTRAL AREA LATE THIS
EVENING. LATE TONIGHT AND WED...NEXT LOW WILL CAUSE FLOW TO BACK
TO MORE OFFSHORE AND WILL SEE INCREASING WINDS OVER MAINLY THE N-S
CHANNELS DURING THE DAY. MUCH OF THE N-S INNER CHANNELS WILL SEE
SCA LEVEL WINDS...WITH GALES LIKELY FOR NRN LYNN CANAL AND
POSSIBLY CLARENCE STRAIT WED AFTERNOON. WILL ALSO HAVE GALES FOR
THE SERN GULF S OF CAPE EDGECUMBE WED.

OTHERWISE...MAY SEE SOME SNOW MIX IN AT TIMES ALONG THE HAINES
HIGHWAY TONIGHT...BUT EXPECT NO ACCUMS. WHITE PASS MAY GET A
COUPLE OF INCHES OF SNOW TONIGHT.

.LONG TERM...LONG RANGE PERIOD REMAINS ACTIVE THOUGH NOT AS
ACTIVE AS IT HAS BEEN RECENTLY. BROAD UPPER TROUGH OVER THE GULF
AND NORTHERN PACIFIC WILL GRADUALLY TIGHTEN AND GET FORCED EAST BY
A SHORT WAVE RIDGE COMING IN FROM THE WEST LATE WEEK. PATTERN
BECOMES MORE PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK AS THE RIDGE AND UPSTREAM TROUGH WORK THEIR WAY THROUGH THE
AREA.

AT THE SURFACE, FIRST CONCERN IS A STRONG LOW SLOWLY MOVING INTO
THE SE GULF FROM THE SOUTH WED NIGHT INTO THU. LOTS OF MODEL
DIFFERENCES ON DISPLAY WITH THIS SYSTEM AS THEY TRY TO SIMULATE
WHAT WILL HAPPEN TO THE LOW AS IT TRANSITIONS OUT OF THE HIGHER
STEERING FLOW ALOFT. THE GFS IS A VERY OBVIOUS OUTLIER BRINGING THE LOW
UP MUCH QUICKER AND WEAKER THEN EVERYTHING ELSE. THE 12Z NAM ALSO
WAS AN OUTLIER BUT IN THE OTHER DIRECTION BEING TOO SLOW. THE GEM
AND ECMWF HAVE KEPT A MIDDLE OF THE ROAD ROUTE WITH TIMING AND
WITH RECENT RUNS HAVE TRENDED A SLIGHT BIT DEEPER AND SLOWER.
LENDING SUPPORT TO THIS IS THE NEW 18Z NAM WHICH HAS SPED UP ITS
TIMING TO BETTER MATCH WHAT THE GEM AND ECMWF ARE SHOWING. AS SUCH
MAIN GUIDANCE WAS THE GEM AND ECMWF FOR THE WED NIGHT THROUGH FRI
PERIOD. THIS RESULTED IN A SLIGHTLY DEEPER LOW THEN WHAT THE
PREVIOUS FORECAST HAD BUT STILL DISPLAYS GALE FORCE WINDS IN THE
SE GULF AND THE POTENTIAL FOR STRONG WINDS ALONG THE OUTER COAST
AND SOUTHERN PANHANDLE THU. AS FOR PRECIP, EVERYWHERE IS STILL TOO
WARM FOR SNOW, EXCEPTION IS WHITE PASS AND POSSIBLY HAINES HIGHWAY
NEAR THE BORDER BUT PRECIP WILL BE HARD PRESSED TO MAKE IT THAT
FAR NORTH WITH THE EASTERLY FLOW. 6 HR RAINFALL AMOUNTS WILL BE IN
THE .1 TO .3 INCH RANGE WITH SOME LOCAL LOWER OR HIGHER AMOUNTS
DUE TO TERRAIN EFFECTS.

AFTER THU NIGHT THE PANHANDLE ENTERS A QUIETER PERIOD THROUGH SAT
AS WE SETTLE UNDER THE UPPER TROUGH AXIS AND THE LEE SIDE OF THE
NEXT UPPER RIDGE. SW FLOW WILL CONTINUE THROUGH THE EARLY WEEKEND
BRINGING SHOWERS AND CONTINUED MILD WEATHER.

NEXT SYSTEM COMES ON SUN AS THE NEXT UPPER TROUGH ENTERS THE GULF.
THIS LOW LOOKS LIKE IT WILL BE WEAKER THEN THE ONES SEEN EARLIER
THIS WEEK ONLY DROPPING TO AROUND 980 MB. IT WILL ALSO TRACK
FARTHER WEST OVER THE WESTERN GULF. THE ASSOCIATED FRONT IS
LOOKING TO BE AROUND GALE FORCE AS WELL. MODEL AGREEMENT IS NOT
GREAT WITH THE STRUCTURE OR TRACK AT THE MOMENT BUT IT IS CLOSE
ENOUGH FOR CONFIDENCE IN THE FORECAST TO BE HIGHER THEN NORMAL FOR
THIS FAR OUT IN THE FORECAST. DECIDED ON USING THE WPC DATA TO TRY
AND SMOOTH OUT THE DIFFERENCES THAT WERE APPARENT IN THE EXTENDED
FORECAST.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ027-028.
MARINE...GALE WARNING FOR PKZ012-036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ011-013-031-033>035-043-051-052.

&&

RWT/EAL

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