Small Craft Advisory 536, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
357 PM AKDT THU SEP 20 2012

.SHORT TERM...UPPER RIDGE JUST E OF THE AREA WILL SLOWLY WEAKEN
THROUGH FRI. AN OCCLUDED FRONT WILL REMAIN OVER THE WESTERN GULF
AND SLOWLY WEAKEN THROUGH FRI. A WEAK SHORTWAVE WILL MOVE NWD
THROUGH THE ERN GULF AND NRN SE AK LATE TONIGHT AND FRI MORNING.
ENDED UP USING A GFS/EC/UKMET BLEND FOR TONIGHT AND FRI...AS NAM
WAS HAVING SOME ISSUES WITH ITS PRESSURE FIELDS OVER THE NRN
GULF.

 MAIN FORECAST ISSUES WILL BE HOW MUCH FOG WILL
DEVELOP...CLOUDS...AND PRECIP POTENTIAL ALONG THE NORTH GULF
COAST. MODEL SOUNDINGS SUGGEST THERE SHOULD BE SOME RADIATION FOG
FORMING OVER MUCH OF THE INNER CHANNEL AREAS TONIGHT BUT
DISSIPATING AGAIN BY FRI AFTERNOON. MARINE FOG WILL BE INCREASING
OVER THE GULF TONIGHT IN THE VERY STABLE ENVIRONMENT THERE...WITH
SOME LOW CLOUDS AND MARINE FOG MOVING NWWD INTO THE SRN AREA LATE
TONIGHT BUT DISSIPATING AWAY FROM THE LAND AREAS BY FRI
AFTERNOON.

 AS FOR CLOUDS...STILL SOME CLOUDS TRAPPED UNDER THE INVERSION
FROM ABOUT THE PAJN AREA NWWD. THINK THE PAJN AREA CLOUDS WILL
SCATTER OUT LATE THIS AFTERNOON BUT REFORM THIS EVENING...WHILE
AREAS TO THE NW REMAIN MOSTLY CLOUDY. THERE WILL BE A BAND OF
MID-LEVEL CLOUDS THAT MOVES NNE ACROSS THE NRN AREA AHEAD OF THE
SHORTWAVE TROF MOVING THRU THE ERN GULF. ONCE THE SHORTWAVE GETS
FURTHER N CLOUDS WILL DECREASE SOME AROUND THE PAJN/PAGN AREAS
FRI AFTERNOON...BUT EXPECT THEM TO HANG AROUND TO THE NW OF THAT
AREA THROUGH FRI AFTERNOON.

 PRECIP WISE...THE PAYA AREA IS GETTING INTERMITTENT LIGHT RAIN
AND DRIZZLE LATE THIS AFTERNOON. THINK THIS WILL DIMINISH EARLY
THIS EVENING BUT PICK BACK UP LATER TONIGHT INTO FRI MORNING AS
WEAK SHORTWAVE MOVES NWD THROUGH THE AREA. PRECIP SHOULD DIMINISH
AGAIN FRI AFTERNOON ONCE SHORTWAVE MOVES PAST THEM. WILL KEEP
LIKELY POPS FOR THE PAYA ZONE TONIGHT AND FRI...BUT MENTION
MAINLY AFTER MIDNIGHT FOR TONIGHT AND MAINLY IN THE MORNING FOR
FRI.

.LONG TERM...FRIDAY NIGHT UPPER LOW IN THE WESTERN GULF OF ALASKA
WILL DRIVE A SURFACE FRONT INTO THE EASTERN GULF BY SATURDAY. THIS
WILL BOOST WINDS ALONG THE OUTER WATERS AHEAD OF THE FRONT TO GALE
LEVELS STARTING WITH CAPE SUCKLING SATURDAY MORNING TO BARANOF
ISLAND OUTER WATERS BY SATURDAY AFTERNOON. LIKEWISE WINDS THROUGH
OCEAN ENTRANCES WILL RISE BY SATURDAY AFTERNOON TO SMALL CRAFT
LEVELS AND RUN THROUGH FRONTAL PASSAGE SATURDAY NIGHT. AN UPPER
LEVEL LOW OFFSHORE OF VANCOUVER ISLAND STILL CONTRIBUTES SOME
MOISTURE FOR PRE-FRONTAL SLIGHT CHANCES OF RAIN FRIDAY NIGHT
THROUGH SATURDAY MORNING FOR COASTAL PANHANDLE AS WELL AS SOUTHERN
ZONES, BUT DESPITE CONTINUED HIGHER POPS BY SREF...NAM...AND
EC...THINK RIDGE ALOFT WILL DEPRESS RAIN CHANCES HERE. FOR PARTLY
CLOUDY AREAS FROM ICY STRAIT SOUTHEAST INCLUDING THE POSSIBILITY
OF A MARINE LAYER IN THE FAR SOUTH WENT KEPT PATCHY FOG AS
POSSIBILITY FOR LATE FRIDAY NIGHT.

RAIN SPREADS OVER SE ALASKA FROM THE NORTHEAST GULF COAST INTO THE
INTERIOR AND SOUTHERN ZONES BY SATURDAY NIGHT. AS PRESSURE
GRADIENT RELAXES OVER THE GULF LATE SATURDAY NIGHT INTO
SUNDAY...LYNN CANAL GETS ACTIVE WITH SCA WINDS APPEARING IN THE
SOUTHERN PART BY SUNDAY. ONE ISSUE THAT TOOK SOME TIME WAS WIND
DIRECTION IN CROSS SOUND AND ICY STRAIT SATURDAY NIGHT INTO SUNDAY
NIGHT. FOR THE MOST PART THINK WINDS WILL REMAIN EASTERLY EVEN
THROUGH FRONTAL PASSAGE...BUT CONFIDENCE LOW ON WHEN TO CHANGE. AT
THIS POINT THINK THE SHIFT TO WESTERLY WILL OCCUR LATE
SUNDAY...PERHAPS SUNDAY AFTERNOON. HOWEVER WENT WITH EAST WINDS
SUNDAY SINCE WINDS WILL BEGIN DECREASE. RAIN WILL TRANSITION TO
OROGRAPHIC SHOWERS FOLLOWING FRONTAL PASSAGE SATURDAY NIGHT AND
WILL LIKELY SQUEEZE HEAVIER AMOUNTS WEST OF YAKUTAT.

FOR MONDAY AND BEYOND...PROGRESSIVE PATTERN LIKELY TO CONTINUE
WITH RAIN CHANCES EACH DAY...AT TIMES RAIN WILL BE LIKELY. EXPECT
SEASONAL TEMPERATURES WITH MAINLY CLOUDY SKIES.

LEANED ON NAM WITH SOME GFS THROUGH SATURDAY FOR WINDS THEN WENT
PRINCIPALLY NAM THROUGH SUNDAY. FROM SUNDAY NIGHT AND BEYOND BASED
WINDS OFF HPC GUIDANCE. FOR PRECIP USED A COMBINATION OF
SREF...EC...NAM...GFS AND GEM. CONFIDENCE FAIRLY GOOD THROUGH
SUNDAY BUT BEYOND DROPS FAST.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043-051.

&&

RWT/JWA