Small Craft Advisory 336, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
159 PM AKDT THU MAY 24 2012

.SHORT TERM...SURFACE HIGH PRESSURE RIDGE OVER THE EASTERN GULF
SHIFTS EAST OVER SOUTHEAST ALASKA AND WEAKENS THROUGH FRIDAY. A
WEAK MID LEVEL TROUGH OVER THE NORTH CENTRAL GULF MOVES EAST AND
DISSIPATES AS IT MOVES ACROSS THE NORTHERN PANHANDLE FRIDAY. A
FRONT ENTERING THE SOUTHWEST GULF THIS EVENING MOVES TO THE
EASTERN GULF FRIDAY AFTERNOON.

 THE RIDGE OVER THE EASTERN GULF IS CAPPING AN EXTENSIVE MARINE
LAYER OVER OUR COASTAL WATERS TODAY. SATELLITE IS SHOWING THE
STRATUS THAT HAS PUSHED INTO THE INNER CHANNELS THIS MORNING BUT
IS SLOWLY DISSIPATING AND EXPECTING PARTLY CLOUDY TO SUNNY
CONDITIONS THIS EVE FOR ALL BUT COASTAL AREAS. STRATUS ACROSS THE
GULF WILL RENEW ITS PUSH ONSHORE THIS EVENING IN WESTERLY FLOW
AND EXPECT THIS TO CONTINUE INTO INNER CHANNELS BY LATE TONIGHT.
LOWEST CONDITIONS WILL BE ALONG THE COAST WHERE LIFR CIGS ARE
POSSIBLE. ALSO WITH BREAKS IN CLOUD COVER...TEMPS COOL QUICKLY
TONIGHT. WITH HIGHER DEW POINTS IN PLACE WILL LIKELY SEE PATCHY
FOG FOR MOST PUBLIC AREAS LATE TONIGHT INTO EARLY FRIDAY. DO HAVE
FAVORABLE SW GRADIENT ORIENTATION ACROSS LYNN CANAL AND HAVE
WINDS INCREASING TO SMCR LEVELS LATE AFTERNOON AND EVENING.
ELSEWHERE EXPECT A LOCAL SEA BREEZES 10 TO LOCALLY 20 MPH.

 WEAK MID LEVEL TROUGH WILL PUSH ACROSS YAKUTAT AREA LATE TONIGHT
WITH RAIN LIKELY. THIS FEATURES SEEMS TO DISSIPATE AS IT CROSS
NORTHERN SE ALASKA ON FRIDAY. ONLY THINKING WILL SEE INCREASING
CLOUDS AS THIS MOVES THROUGH. SOUTHEAST CORNER OF PANHANDLE WILL
BE PARTLY CLOUDY AGAIN ON FRIDAY AND HAVE TEMPS IN LOWER TO MID
60S TO AROUND 70 FOR HYDER. SOUTHERN COAST WILL HAVE STRATUS MOVE
ONSHORE LATE TONIGHT BUT BURN OFF FRIDAY MORNING.

 SECOND STRONGER FRONT WILL SPREAD SMCR SE WINDS TO OFFSHORE
WATERS EARLY FRIDAY AND THROUGH OUR COASTAL WATERS BY FRIDAY
AFTERNOON. FRONT MOVES TO COASTAL WATERS BY FRIDAY AFTERNOON BUT
BECOMES STATIONARY AND SHEARS OUT A BIT. WILL HAVE RAIN FOR PAYA
AND FAR NORTH COASTAL AREAS AND A CHANCE FOR NE CORNER OF SE
ALASKA. AMOUNTS NOT EXPECTED TO BE SIGNIFICANT.

.LONG TERM...MODELS IN GOOD AGREEMENT ON THE LARGE SCALE PATTERN
THRU NEXT WEEK. UPPER LOW WILL MOVE NE INTO THE GULF BY LATE FRI
NIGHT...THEN REMAIN OVER THE GULF THRU ABOUT MON. A LARGER UPPER
LOW WILL MOVE INTO THE GULF BY MIDWEEK...AND THIS WILL HELP KICK
FIRST UPPER LOW TO THE NW AND OUT OF THE GULF. MODELS DO DIFFER ON
THE SHORTWAVE FEATURES EVEN EARLY ON. AFTER COORD WITH WFO
PAFC...DECIDED TO BLEND THE 00Z ECMWF WITH PREVIOUS GRIDS FROM 03Z
SAT TO 06Z MON...THEN HPC/EC BLEND FROM 12Z MON TO 12Z TUE...THEN
STRAIGHT HPC AFTER THEN. HPC USED AN ENSEMBLE APPROACH WHICH
LOOKED REASONABLE GIVEN THE MODEL DIFFERENCES...BUT WANTED TO
BLEND IN ECMWF EARLY ON DURING THE HPC PERIOD TO STRENGTHEN THE
SFC LOW OVER THE GULF A BIT.

FOR FRI NIGHT INTO THE WEEKEND...A WEAKENING FRONT WILL BE PUSHING
SLOWLY ONSHORE AND LOOKS LIKE IT WILL BE E OF THE AREA BY LATE SAT
NIGHT. FRONT WILL BE SOMEWHAT FORWARD SLOPED SO UPPER PART OF
FRONT WILL BE WELL EAST OF THE AREA WHILE LOWER PART OF FRONT IS
STILL OFFSHORE. LOOKS LIKE BEST THREAT FOR PRECIP FROM IT IS WHEN
LOWER PART OF THE FRONT MOVES ONSHORE. THERE COULD BE SOME
SPRINKLES OR SPOTTY LIGHT RAIN AS MIDDLE PART OF THE FRONT MOVES
THRU FRI NIGHT...ENOUGH TO WARRANT CHANCE POPS WELL OUT AHEAD OF
THE LOWER LEVEL PART OF THE FRONT. ONCE THE ENTIRE FRONT MOVES
THRU WILL BE IN WEAK ONSHORE FLOW IN LOWER LEVELS FOR A SHORT TIME
UNTIL THAT FLOW BECOMES MORE SELY SUN AHEAD OF A WEAK SFC TROF. MAY
BE A SHORT BREAK IN PRECIP AFTER FRONT HAS GONE COMPLETELY INLAND
BUT THAT NEXT TROF WILL BRING IN A BETTER THREAT FOR PRECIP SUN.

FOR NEXT WEEK...EVENTUALLY THE UPPER LOW OVER THE GULF WILL OPEN
UP AND LIFT NWWD AHEAD OF THE LARGER UPPER LOW MOVING IN FROM THE W.
THIS LARGER UPPER LOW WILL SEND A FRONT NE INTO THE SERN GULF
TUE...WITH SLOW PROGRESS ONSHORE DURING MIDWEEK AS THERE MAY BE
ONE OR MORE LOW PRESSURE WAVES THAT MOVE ALONG THE FRONT. THIS
WILL TEND TO KEEP THE HIGHER PRECIP THREAT OVER THE S TUE INTO
WED. ENDED UP BOOSTING TEMPS A FEW DEGREES ESPECIALLY DURING THE
DAYTIME GIVEN THE SELY FLOW NEXT WEEK...BUT NOT AS MUCH AS THE MOS
GUIDANCE WARMS US UP. WANT TO WAIT AND GET A BETTER FEEL ON TIMING
OF ANY PRECIP AREAS BEFORE TRYING TO WARM THINGS UP TOO MUCH.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-052.

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MM/RWT