617
FXAK67 PAJK 090054
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
354 PM AKST SUN NOV 8 2009
SHORT TERM
LOW OVER THE NE GULF WILL DRIFT WWD AND SLOWLY
WEAKEN THRU MON. A DEVELOPING LOW ABOUT 150 NM SW OF THE
CHARLOTTES WILL MOVE N INTO THE SE GULF THIS EVENING...THEN DRIFT
NW BUT REMAIN OVER THE SE GULF LATER TONIGHT INTO MON. ASSOCIATED
OCCLUDED FRONT WILL MOVE N INTO THE SRN AREA THIS EVENING...THEN
GO ALOFT AS IT MOVES INTO THE CENTRAL AND NRN AREAS LATE TONIGHT
AND MON MORNING. SECOND WRAP OF FRONT WILL BE AFFECTING THE SRN
COASTAL AREA TONIGHT AND CENTRAL COAST FROM PASI SWD MON.
SEVERAL FORECAST CONCERNS FOR TONIGHT AND MON. AM CONCERNED
ABOUT HOW MUCH WIND WILL OCCUR OVER THE SRN AREA ESPECIALLY ALONG
THE SRN OUTER COAST TONIGHT AND CENTRAL COAST MON. SHOULD BE A
BAND OF ADVY LEVEL WINDS AFFECTING SRN COAST BEGINNING EARLY THIS
EVENING WITH OCCLUDED FRONT...THEN ANOTHER ROUND OF ADVY WINDS
THERE LATER TONIGHT AS SECOND WRAP BEGINS TO AFFECT THEM. MAY
ALSO SEE A SHORT PERIOD OF ADVY LEVEL WINDS IN ZONE 28 BUT LESS
CONFIDENT THERE. THEN SECOND WRAP WILL AFFECT THE CENTRAL COAST
MON AND IT LOOKS LIKE THE AREA FROM PASI SWD WILL SEE ADVY LEVEL
GUSTS...ESPECIALLY AROUND PORT ALEXANDER. PLAN TO ISSUE A WIND
ADVY FOR TONIGHT IN ZONE 27 AND MON FOR ZONE 23. DO NOT PLAN ON
ISSUING AN ADVY FOR 28 BUT WILL KEEP AN EYE ON THINGS AS FRONT
APPROACHES THEM THIS AFTERNOON. WILL HAVE GALES FOR WATERS
ADJACENT TO THE ADVY AREA AS WELL AS CLARENCE STRAIT TONIGHT INTO
MON MORNING AT LEAST. FURTHER N...WILL LIKELY SEE SCA LEVEL N
WINDS IN THE N-S CHANNELS FOR A BIT LATER THIS EVENING AND
OVERNIGHT...BUT THOSE SHOULD DIMINISH MON AS FRONT MOVES LAST
THEM ALOFT. THE MORE E-W CHANNELS SHOULD STAY AT SCA LEVELS
THOUGH THRU MOST OF MON.
SECOND CONCERN IS POTENTIAL FOR TSTMS. ATTM...SOME LIGHTNING HAS
OCCURRED ALONG THE OCCLUDED FRONT...BUT MODELS SUGGEST THAT THE
CAPE WILL BE DECREASING AND SOME WEAKENING OF THE FRONT SHOULD
OCCUR BY TIME IT GETS INTO THE SRN AREA. WILL KEEP AN EYE ON THIS
AND MAKE FINAL DECISION ON WHETHER TO ADD PRE-FRONTAL TSTMS TO
THE FAR SRN AREAS THIS EVENING CLOSER TO ISSUANCE TIME. OTHER
THREAT FOR TSTMS WOULD BEGIN EARLY MON AS MID-LEVEL COLD POOL
WRAPS AROUND LOW INTO THE SRN AREA. CAPE FORECAST FOR THE FAR S
IS MARGINAL FOR TSTMS...BUT MID-VORT FIELD WILL BE SOMEWHAT
CHANNELED. ATTM...AM GOING TO KEEP MENTION OUT FOR MON AS WELL.
AS FOR PRECIP...RAIN WITH THE FRONT SHOULD REACH SRN AREA BY
EARLY EVENING...THEN REACH S-CENTRAL AREA BY LATE EVENING. AS
BAND CONTINUES FURTHER N...IT SHOULD BEGIN TO WEAKEN RAPIDLY DUE
TO THE OFFSHORE FLOW AHEAD OF IT AND THE FRONT GOING ALOFT. WILL
KEEP HIGHEST POPS WITH FRONT MAINLY OVER THE SRN HALF OF THE
AREA. AS FRONT GOES BY HOWEVER...THE OFFSHORE COMPONENT TO FLOW
WILL WEAKEN FOR A SHORT PERIOD AND ALLOW SOME LIGHT PRECIP AS FAR
N AS PAJN- PAEL CORRIDOR LATE TONIGHT OR EARLY MON...BEFORE
OFFSHORE FLOW INCREASES AGAIN OVER THE N LATER MON.
AS FOR THE ONGOING SHOWERS OVER THE AREA...THEY SHOULD RAPIDLY
DIMINISH FROM S TO N THIS EVENING. THE PAYA AREA WILL LIKELY SEE
SOME CLEARING LATER TONIGHT AS FLOW BECOMES OFFSHORE THRU A DEEPER
LAYER...AND MON WILL LIKELY REMAIN NICE THERE.
LONG TERM
/MON NIGHT THROUGH SUN/
LARGE SCALE WEATHER PATTERN FORECAST BY GLOBAL MODELS TO BE
PROGRESSIVE DURING THE WEEK. ONE AREA OF LOW PRESSURE IN ERN GULF
GRADUALLY FILLS AND GETS SHOVED INLAND WED BY APPROACHING HIGH
PRESSURE RIDGE. RIDGE IS ONLY TEMPORARY. MODELS AGREE A STRONG
COLD FRONT WILL PUSH ACROSS THE GULF ON THUR AND INLAND BY FRI.
CONFIDENCE IN THE DETAILS AFTER WED IS ONLY MEDIUM BECUASE OF
DIVERGENT SOLUTIONS BETWEEN GFS/ECMWF/UKMET. ENSEMBLE SOLUTIONS
SHOW GREATEST SPREAD OVER PANHANDLE FRI.
ALTHOUGH OPERATIONAL MODELS KEEP LOW PRESSURE LINGERING OVER ERN
GULF TUE-WED THE UPPER LEVEL LONG WAVE PATTERN HINTS AT RIDGING
BUILDING IN FROM THE WEST. CHC FOR SHOWERS WIL BE HIGHEST SRN HALF
OF PANHANDLE TUE-WED WHILE NRN HALF MAY BENEFIT FROM A DRIER
OFFSHORE WIND DIRECTION N OF THE SFC LOW FCST TO GET TO ABOUT
SITKA SOUND AND STALLING. AS RIDGE APPROACHES UPPER LEVEL
SUBSIDENCE MAY ALSO HELP TO DIMINISH SHOWER ACTIVITY FROM NW TO
SE. SOME CLEARING POSSIBLE FAR NORTH TUES NIGHT MAY ALLOW FOR
COLD MORNING WED WITH TEMPS IN MID 20S IN YAKUTAT AND
HAINES/SKAWGWAY ZONES. BUT THE RIDGE AXIS MOVES QUICKLY
PAST...FASTER AND FLATTER IN EURO MODEL...SLOWER AND MORE
AMPLITUDE IN GFS. UKMET MODEL PREFERRED SLIGHTLY AS A COMPROMISE
AND IS SUPPORTED BY NCEP DISCUSSIONS TODAY TOO. LONG RANGE GRIDS
CHANGED ONLY SLIGHTLY BY BLENDING IN HPC GUIDANCE TO EXISTING
GRIDS.
UPPER LEVEL WAVE FEATURES OF FRONTAL SYSTEM ON THU VARY DEPENDING
UPON MODEL. I EXPECT STEADY AND POSSIBLY HEAVY PRECIP ON THUR
DRAGGING FROM NRN ZONES TO SOUTHERN ZONES OVER 24HRS TO FRI
MORNING. THICKNESS PROGS INDICATE VERY SHARP GRADIENT ALG FRONT
AND VALUES DIPPING INTO THE 515 TO 520 DM RANGE SO SNOW IN FCST
NEAR END OF PERIOD LOOKS LIKE A GOOD BET NORTH OF JUNEAU-CROSS
SOUND.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND ADVISORY UNTIL 6 AM AKST MONDAY FOR AKZ027.
WIND ADVISORY FROM 6 AM TO 3 PM AKST MONDAY FOR AKZ023.
MARINE...GALE WARNING FOR PKZ036-041-042-052.
SMALL CRAFT ADVISORY FOR PKZ011>013-021-022-031>035-043-051.
RWT/TA
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