Gale Warning 264, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
537 AM AKDT SUN OCT 19 2014

.SHORT TERM...A COMPLEX LOW PRESSURE AREA OVER THE S-CENTRAL GULF
WILL DRIFT N THEN NW INTO THE NW GULF BY LATE TONIGHT. A LOW
DEVELOPING NEAR SRN HAIDA GWAII WILL MOVE N THRU SE AK THIS
AFTERNOON AND EVENING. A TROF EXTENDING S FROM THE S-CENTRAL GULF
LOW WILL SLOWLY LIFT NE TOWARD THE SE GULF BY LATE TONIGHT. MODELS
WERE STRUGGLING SOME WITH THE LOW NEAR SRN HAIDA GWAII...AND ENDED
UP USING A 06Z NAM/00Z ECMWF/00Z GEM BLEND TO GET BEST HANDLE ON
THIS SYSTEM.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL...WINDS...AND
CHANCES FOR TSTMS. RIGHT NOW A BAND OF SHOWERS IS OVER THE NW
THIRD OF THE AREA...WITH SPOTTIER SHOWERS OVER THE CENTRAL AREA.
THINK THIS BAND WILL MOVE WNW AND BE MAINLY W OF PAYA AND N OF
PAGY BY LATE THIS MORNING. THE SPOTTIER SHOWERS TO THE S OF THAT
AREA WILL DIMINISH THIS MORNING AS INCREASING OFFSHORE FLOW
DEVELOPS AHEAD OF LOW MOVING N FROM NEAR SRN HAIDA GWAII. RAIN
FROM THIS LOW IS JUST REACHING THE FAR SRN AREA...AND SHOULD
SPREAD NWD INTO THE S-CENTRAL AREA BY LATE MORNING...THE N-CENTRAL
PANHANDLE THIS AFTERNOON...AND FINALLY THE FAR NRN AREA BY EARLY
THIS EVENING. ONCE LOW MOVES PAST THE AREA...PRECIP SHOULD
TRANSITION BACK TO SHOWERS OVER THE MAIN PART OF THE PANHANDLE FROM
THE S TONIGHT. THE PAYA AREA SHOULD SEE AN INCREASING THREAT FOR
SHOWERS TONIGHT AS LOW LEVEL FLOW BECOMES MORE ONSHORE.

WIND WISE...NLY PRESSURE GRADIENTS WILL INCREASE TODAY OVER THE
CENTRAL AND NRN AREAS. THINK 20-30 KT NLY WINDS WILL DEVELOP IN
THE MORE N-S CHANNELS N OF FREDERICK SOUND BY THIS AFTERNOON.
FURTHER S...STRONGEST WINDS ARE EXPECTED AS LOW MOVES INTO THE FAR
SE GULF THIS AFTERNOON. LOW LEVEL SELY JET OF 40-50 KT IS EXPECTED
TO REACH MAINLY THE SRN INNER CHANNELS IN THE AFTERNOON...AND THIS
WILL LIKELY RESULT IN A PERIOD OF STRONG WINDS/GALES FOR THAT
AREA. MODELS DIFFERED ON HOW FAR W THESE STRONGER WINDS WERE...AND
THIS MADE THE SRN OUTER COAST WIND FORECAST TRICKY. DECIDED NOT TO
BRING IN STRONG WINDS TO ZONE 27 AT THIS POINT...BUT DAY SHIFT
WILL NEED TO WATCH HOW MUCH THE LOW DEEPENS AND WHERE THE LOW
LEVEL JET AXIS SETS UP. ELSEWHERE OVER THE GULF...WILL HAVE SOME
SCA LEVEL WINDS OVER THE NRN GULF...AND TO THE S-SW OF THE
LOW/TROF OVER THE GULF AS WELL AS COLD ADVECTION INCREASES FROM
THE W THRU TONIGHT. WHERE WINDS DO NOT REACH SCA LEVELS OVER THE
GULF COASTAL WATERS...SEAS WILL REMAIN HIGH ENOUGH FOR SCA DUE TO SEAS.

AS FOR THE TSTM THREAT...MODELS SUGGEST HIGHEST CAPE VALUES (300+ J/KG)
WILL SPREAD IN FROM THE S. MUCH OF THE CENTRAL GULF WILL BE
UNSTABLE TODAY...BUT THE FAR ERN GULF WILL TEMPORARILY STABILIZE
AS LOW MOVES N FROM HAIDA GWAII. ONCE LOW MOVES PAST THE
AREA...INSTABILITY WILL INCREASE FROM THE SW OVER THE ERN
GULF...BUT AS TROF LIFTS NE TONIGHT...THE MOST UNSTABLE LAYER WILL
GET SQUEEZED FROM THE SW BY THE TROF. WILL KEEP IN ISOLATED TSTMS
OVER MUCH OF THE CENTRAL GULF TODAY...THEN SHIFT TO THE ERN GULF
TONIGHT WHILE DIMINISHING THE THREAT OVER THE CENTRAL GULF. BEST
CHANCES FOR ANY LAND AREAS GETTING TSTMS ARE ALONG THE CENTRAL
AND SRN COASTAL AREA TONIGHT.

.LONG TERM...LONG RANGE FORECAST CONTINUES TO SEE WET WEATHER AS A
DEEP UPPER TROUGH REMAINS ROOTED OVER THE CENTRAL GULF THROUGH AT
LEAST LATE WEEK. THE MAIN JET ENERGY HAS BEEN PUSHED WELL TO THE
SOUTH BECAUSE OF THE TROUGH AS A RESULT ANY STORMS THAT FIND THEIR WAY
INTO THE GULF ARE STUCK THERE FOR QUITE AWHILE DUE TO WEAK
STEERING CURRENTS UNDER THE TROUGH AXIS. THERE IS A BIT OF HOPE IN
BREAKING UP THIS PATTERN BUT IT DOES NOT SHOW UP UNTIL NEXT
WEEKEND IN THE FORM OF A SLOW MOVING UPPER LOW HEADING EAST OUT OF
RUSSIA.

AT THE SURFACE WE ARE FINALLY GETTING RID OF ONE LOW ONLY FOR IT
TO BE REPLACED BY ANOTHER OF SIMILAR STRENGTH AND STAYING POWER.
THE DEPARTING LOW IS GETTING SHOVED UP TO COOK INLET MON WHILE IT
WEAKENS AND ELONGATES. THIS STRENGTHENS AN EXISTING SURFACE TROUGH
THAT WAS ALREADY EXTENDING FROM THE LOW INTO THE SE GULF. THAT
TROUGH WILL HEAD NE OVER THE PANHANDLE MON AFTERNOON ENHANCING THE
SHOWERS STILL LINGERING OVER THE AREA. THERE IS ENOUGH UPPER LEVEL
VORTICITY COMBINED WITH A WEDGE OF SOME UPPER LEVEL COOLER AIR
ALONG THIS TROUGH THAT SOME SHOWERS MAY BE STRONG ENOUGH TO BE
THUNDERSTORMS ALONG THE OUTER COAST AND SOUTHERN PANHANDLE MON.

BEHIND THE TROUGH SHOWERS WILL START TO DIMINISH MON NIGHT AS SOME
WEAK RIDGING MOVES INTO THE PANHANDLE. THIS WILL NOT LAST AS THE
NEXT STORM COMES ROLLING IN FROM THE SOUTH. THIS LOW WILL ALMOST
TAKE THE SAME TRACK AS THE PREVIOUS STORM WITH THE MAIN LOW
SPIRALING AROUND THE CENTRAL GULF WHILE A GALE FORCE FRONT HITS
THE PANHANDLE FROM SOUTH TO NORTH TUE AFTERNOON AND TUE NIGHT.
MODEL AGREEMENT HAS IMPROVED WITH THIS SYSTEM OVER THE LAST 24
HOURS BUT THERE IS STILL ROOM FOR IMPROVEMENT. MODEL AGREEMENT ON
THE TRACK FOR THIS STORM IS DECENT UP UNTIL IT STARTS RETROGRADING
BACK TO THE WEST TUES NIGHT THEN MODELS START DIVERGING FROM
THERE. IN ANY CASE, THE PANHANDLE IS IN FOR MORE WET WEATHER WITH
WIND EXPECTED FOR THE OUTER COAST AND SOUTHERN PANHANDLE MID WEEK.
BY LATE WEEK THE LOW WILL STILL BE SPIRALING IN THE SOUTHERN GULF
BUT IT MAY HAVE SLIPPED FAR ENOUGH SOUTH THAT NORTHERLY WINDS IN
THE PANHANDLE MAY START DRYING OUT THE NORTHERN HALF OF THE
PANHANDLE. NOT ENTIRELY CONFIDENCE ON THIS BUT THE POSSIBILITY IS
THERE FOR SOME RELIEF FROM THE WET WEATHER AT LEAST FOR THE NORTH.

LONG RANGE MODELS WERE IN GOOD AGREEMENT THROUGH ABOUT TUE THEN
START DIVERGING AS THEY HAVE TROUBLE WITH WHERE THE SECOND LOW
WILL DRIFT IN THE WEAK STEERING FLOW UNDER THE UPPER TROUGH AXIS.
MOST OF THE CHANGES WERE MADE IN THE TUE TO WED TIME PERIOD ADDING
MORE DETAILS TO THE MAIN FRONT OF THE SECOND LOW. MAIN CHANGES
WERE UPPING WINDS AND SEAS ALONG THE MAIN FRONT AS IT COMES NORTH.
USED GFS AND EC FOR MAIN WIND GUIDANCE. WPC WAS USED FOR LATER
PERIODS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 4 PM AKDT THIS AFTERNOON THROUGH THIS EVENING
     FOR AKZ028.
MARINE...GALE WARNING FOR PKZ036.
         SMALL CRAFT ADVISORY FOR PKZ012-021-022-034-035-041>043-051-052.

&&

RWT/EAL

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