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FXAK67 PAJK 011336
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
536 AM AKDT MON SEP 1 2014

.SHORT TERM...UPPER LEVEL TROUGH IS MOVING SOUTHEAST FROM THE
NORTHERN GULF TO DIXON ENTRANCE BY MIDNIGHT. AM EXPECTING MINOR
RIDGE AT THE SURFACE AND ALOFT AFTER THE TROUGH MOVES THROUGH. THE
TROUGH AXIS IS CLEARING THE PRECIPITATION FROM THE AREAS AS IT
PASSES. AS SUCH SHOWERS ARE EXPECTED TO DIMINISH THROUGH THE DAY
AND OVERNIGHT FOR SOUTHEAST ALASKA.

SHOULD SEE SOME CLEARING OVER THE NORTHEAST GULF COAST AND NORTHERN
PANHANDLE LATE AFTERNOON TO OVERNIGHT TIME FRAME. THIS COMBINED
WITH RECENT RAINS AND LIGHTER WINDS AM EXPECTING SOME PATCHY FOG
TO FORM IN THE COASTAL AREAS. THINK THE AREAS THAT NORMALLY
DEVELOP IT COULD DO SO...SHOULD NOT BE WIDESPREAD OR TO DENSE TO
MY INITIAL THINKING.

WINDS OVER THE GULF WATERS IS BECOMING MORE WESTERLY THROUGH THE
AFTERNOON AND OVERNIGHT GENERALLY IN THE 15 TO 20 KT RANGE AND
EXPECT A SWELL TO KEEP THE SEAS UP FOR COASTAL WATER SOUTH OF
CROSS SOUND ABOVE 8 FT WHERE A SMALL CRAFT IS NEEDED. WINDS IN THE
INNER CHANNELS ARE LOOKING TO STAY LESS THAN 20 KT GENERALLY.

.LONG TERM...AN UPPER-LEVEL SHORTWAVE TROUGH WILL BE IN THE
PROCESS OF EXITING SERN AK DURING TUE AFTERNOON. AS THIS TAKES
PLACE...A MIDLEVEL RIDGE IS FORECAST TO BUILD OVER THE
GULF...WHILE A LARGE CYCLONIC GYRE GRADUALLY MOVES EWD ACROSS FAR
NRN INTERIOR AK AND NWRN CANADA. WEAK EMBEDDED DISTURBANCES
LOCATED BETWEEN THE RIDGE AND CYCLONE WILL PROGRESS ACROSS NRN
PORTIONS OF THE CWA TUE AFTERNOON THROUGH WED NIGHT...WHICH MAY
SUPPORT ISOLATED/SCATTERED SHOWER DEVELOPMENT. IN
ADDITION...SURFACE HIGH PRESSURE BUILDING OVER THE GULF COMBINED
WITH LOW PRESSURE OVER NWRN CANADA WILL AID IN THE DEVELOPMENT OF
SMALL CRAFT SLY WINDS IN NRN LYNN CANAL TUE AND WED.

MEANWHILE...MODEL GUIDANCE IS COMING INTO BETTER AGREEMENT WITH
THE RETURN OF SUBTROPICAL MOISTURE SPREADING NEWD ACROSS THE GULF
DURING THE THU-SAT TIME PERIOD. THE 12Z ECMWF IS STILL A SLIGHTLY
FASTER SOLUTION...BUT THE 06Z GFS AND NAM ARE BEGINNING TO CATCH
UP. THIS RESULTS IN GREATER CONFIDENCE THAT A PROLONGED PERIOD OF
RAIN WILL BE PROBABLE OVER THE REGION DURING THE SECOND HALF OF
THE LONG TERM FORECAST. THE EVOLUTION OF THIS RAINFALL EVENT WILL
BE TIED TO SMALLER-SCALE WAVES EMANATING FROM A TROUGH LOCATED S
OF THE ALEUTIANS...WHICH ARE INHERENTLY HARD TO PREDICT 3-4 DAYS
OUT. THUS...REMAINED CONSERVATIVE WITH REGARD TO POPS AND QPF.
HOWEVER...POTENTIAL EXISTS FOR A MULTI-DAY PERIOD OF MODERATE TO
HEAVY RAIN /SEE HYDRO DISCUSSION BELOW/.

FORECAST CONFIDENCE IS ABOVE AVERAGE THROUGH WED...AND THEN IS
BELOW AVERAGE...THOUGH IMPROVING...THU THROUGH MON. USED A
GFS/SREF BLEND FOR POP/S 15Z TUE-12Z THU...AND THEN ENSEMBLE BLEND
FOR THE REMAINDER OF THE FORECAST. MODEL QPF AMOUNTS WERE VERY
HIGH THU AFTERNOON INTO THE WEEKEND. BUT AS PREVIOUSLY
MENTIONED...CONFIDENCE IS NOT HIGH IN THE TIMING OF SMALLER-SCALE
UPPER WAVES. THUS...CUT RAINFALL AMOUNTS DRAMATICALLY UNTIL
CONFIDENCE IMPROVES. KEPT PATCHY FOG IN THE FORECAST FOR TUE
MORNING AND ADDED PATCHY FOG FOR CNTRL/SRN AREAS TUE NIGHT AND WED
MORNING.

&&

.AVIATION...GENERALLY WIDESPREAD MVFR CEILINGS ACROSS THE
PANHANDLE THIS MORNING LESS THE YAKUTAT REGION THAT IS BEHIND THE
PRIMARY TROUGH MOVING THROUGH. THERE HAVE BEEN A FEW ISOLATED IFR
CEILINGS THIS MORNING. LOOK FOR IMPROVING CONDITIONS FROM WEST AND
NORTHWEST THROUGH THE MORNING HOURS AS THE CLOUDS LIFT AND
SHOWERS TAPER OFF. AM CARRYING A SLIGHT CHANCE OF THUNDER OVER THE
COASTAL WATERS SO FLIGHTS ALONG THE GULF COST FROM CROSS SOUND
SOUTH SHOULD BE AWARE OF THIS.

&&

.HYDROLOGY...A PLUME OF SUBTROPICAL MOISTURE IS FORECAST TO
SPREAD ACROSS SERN AK BY THU AND PERSIST OVER THE REGION THROUGH
SAT. THIS MOISTURE COMBINED WITH A SERIES OF UPPER-LEVEL
DISTURBANCES AND STRONG LOW TO MIDLEVEL SWLY WINDS WILL AID IN THE
POTENTIAL FOR HEAVY RAINFALL. CONFIDENCE IS CURRENTLY LOW WITH
REGARD TO THE EXACT TIMING OF HEAVIER PERIODS OF RAIN...BUT MODEL
GUIDANCE INDICATES A MULTI-DAY PERIOD OF RAINFALL RATES RANGING
FROM 1-3 INCHES PER 12 HRS WILL BE POSSIBLE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041>043.

&&

$$

BEZENEK/GARNER

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