Small Craft Advisory 281, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
524 AM AKDT FRI APR 27 2012

.SHORT TERM...A WEAKENING LOW OVER THE FAR SE GULF WILL
DISSIPATE JUST OFFSHORE THE CENTRAL COAST BY THIS EVENING. A WEAK
FRONTAL ZONE OVER THE NE GULF COAST WILL SLOWLY DISSIPATE THROUGH
TONIGHT. ANOTHER WEAK FRONT WILL MOVE NWD TO JUST S OF THE GULF
BY LATE TONIGHT. USED 00Z ECMWF AS IT HAS BEST HANDLE ON THE LOW
OVER THE SE GULF AND THE WEAK FRONTS.

 MAIN FORECAST ISSUES WILL BE PRECIP POTENTIAL AND WINDS. RIGHT
NOW A BAND OF PRECIP IS OVER THE NE GULF NEAR PAYA ASSOCIATED
WITH THE FRONTAL ZONE THERE. EXPECT THIS PRECIP TO SLOWLY
DIMINISH AS THE FRONT WEAKENS FURTHER THROUGH TONIGHT. ANOTHER
AREA OF PRECIP IS OVER SRN SE PUBLIC...JUST N AND E OF THE LOW OVER
THE FAR SERN GULF. THIS AREA WILL MOVE NWD INTO THE N-CENTRAL
INNER CHANNELS THIS MORNING. AS THE LOW DISSIPATES AND SUPPORTING
UPPER TROF MOVES INLAND LATE THIS AFTERNOON AND EVENING...THE
PRECIP WILL TAPER OFF FROM W TO E OVER THE CENTRAL AND COASTAL
AREAS. HOWEVER...THE SRN INNER CHANNELS WILL LIKELY KEEP SOME
PRECIP GOING TONIGHT AS A MINOR SHORTWAVE MOVES NEWD TOWARD THEM
WITH THE NEXT FRONT. WILL KEEP AT LEAST LIKELY POPS FOR THE FAR
SRN INNER CHANNELS THRU TONIGHT...AND ALLOW POPS ELSEWHERE TO
DROP TO CHANCE OR LESS BY LATE TONIGHT. WILL GO WITH STRATIFORM
WORDING INVOF THE 2 FRONTAL ZONES...AND SHOWER TERMINOLOGY
ELSEWHERE.

 AS FOR WINDS...THE MOST WIND WILL BE ASSOCIATED WITH THE LOW
OVER THE SERN GULF. A BAND OF SCA LEVEL WINDS IS N AND E OF THE
LOW CENTER INCLUDING THE SRN INNER CHANNELS. EXPECT THESE WINDS
TO SLOWLY DECREASE THIS AFTERNOON AND EVENING AS THE LOW WEAKENS
AND EVENTUALLY DISSIPATES. AS THE LOW DRIFTS NWD SOME INCREASE IN
WINDS IS LIKELY OVER THE CENTRAL CHANNELS AS TIGHTER GRADIENT
MOVES IN...BUT THEY SHOULD REMAIN BELOW SCA LEVELS. THERE WILL
ALSO BE SOME 15-20KT+ WINDS OVER FAR NRN LYNN CANAL AND PAGY AREA
THIS AFTERNOON AND EVENING DUE TO ENHANCED TROFFING NEAR PAGY.

 &&

 .LONG TERM...MAIN FORECAST PROBLEM IN THE EXTENDED RANGE
CONTINUES TO BE THE SYSTEM THAT WILL BE COMING ACROSS THE GULF ON
SUN INTO MON. LONG RANGE MODELS SEEM TO FALL INTO TWO DISTINCT
GROUPS REGARDING THIS SYSTEM. THE FIRST IS THAT THE MAIN LOW
STAYS INTACT ACROSS THE GULF AS DEPICTED BY THE EC, UK, AND
SOMEWHAT BY THE NAM. THE SECOND IS THAT THE FIRST LOW HEADS UP TO
JUST SOUTH OF KODIAK AND DISSIPATES WHILE A SECOND LOW IS THE ONE
THAT HEADS ACROSS THE GULF TOWARDS THE PANHANDLE. THIS SECOND
CHOICE IS SUGGESTED BY MAINLY THE GFS. IN EITHER CASE, THE SYSTEM
SENDS A FRONT ACROSS THE GULF AND INTO THE PANHANDLE BRINGING
RAIN AND WIND TO THE PANHANDLE. HIGHEST WINDS APPEAR TO BE MAINLY
IN THE OUTSIDE WATERS AND ALONG THE OUTER COAST BUT STRENGTH
DEPENDS MAINLY ON WHAT EXACT TRACK THE SYSTEM TAKES WHICH IS ALSO
STILL UP FOR DEBATE. DECIDED ON GALES ALONG THE NORTHERN GULF
FROM A BARRIER JET SETTING UP, AND SMALL CRAFT WINDS ALONG THE
REST OF THE GULF SUN INTO SUN NIGHT. SUN INTO SUN NIGHT WILL BE
WHEN THE BULK OF THE PRECIP ARRIVES SO CATEGORICAL POPS HAVE BEEN
POSTED OVER MOST OF THE PANHANDLE THEN.

 FARTHER OUT, DIFFERENCES CONTINUE AS THE MODELS CAN'T QUITE
DECIDE WHAT TO DO WITH THE REMAINS OF THE SYSTEM ONCE IT REACHES
THE EASTERN GULF. CURRENT GFS KEEPS THE LOW SPIRALING AROUND THE
CENTRAL AND EASTERN GULF WELL INTO NEST WEEK. EC ON THE OTHER
HAND KEEPS THE REMAINS UP ALONG THE NORTHERN GULF COAST THROUGH
THE SAME PERIOD. DECIDED TO DROP BACK TO THE HPC DATA WHICH
OFFERED A MUCH BETTER MIDDLE GROUND THAN WHAT WAS DEPICTED
YESTERDAY.

 OVERALL MODELS GENERALLY REPRESENTED THE BIG PICTURE WELL BUT
THE DETAILS ARE STILL SKETCHY. USED A BLEND TO THE 0Z EC WITH
SOME GFS MIXED IN AT TIMES OUT TO MONDAY THEN SWITCHED TO HPC AND
EC FOR MON ONWARD. FORECAST CONFIDENCE IS ABOUT AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ033-035-036-041-042.

&&

RWT/EAL