Small Craft Advisory 309, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
600 AM AKDT WED MAY 9 2012

.SHORT TERM...A WEAK BUT WELL DEFINED LOW SURFACE LOW CROSSED
THE OUTER COAST OVERNIGHT VICINITY CAPE MUZON AT THE SOUTH END OF
DALL ISLAND. AS OF EARLY THIS MORNING, THE LOW WAS OVER MISTY
FJORDS AND HEADED ENE INTO CANADA. RADAR DATA AND SATELLITE
IMAGERY SUGGEST VERY COLD AND CONVECTIVE AIRMASS ASSOCIATED WITH
THE LOW. UPPER AIR DATA FROM WSO ANNETTE ISLAND CONFIRM THE
ATMOSPHERE IS QUITE UNSTABLE. RETAINED ISOLATED THUNDERSTORMS IN
THE FORECAST FOR SOUTHERN PANHANDLE AND INNER CHANNELS, BUT HAVE
NOT YET DETECTED ANY LIGHTNING NOR RECEIVED REPORTS OF LIGHTNING
OR THUNDER FROM SURFACE OBSERVATION SITES. AS THE LOW TRACKS EAST
INTO CANADA, THREAT OF THUNDERSTORMS WILL DIMINISH. CARRIED
ISOLATED THUNDERSTORMS IN MISTY FJORDS INTO THE AFTERNOON, BUT
REMOVED ALL MENTION BY TONIGHT. SHOWER ACTIVITY OVER THE
PANHANDLE WILL DIMINISH SLOWLY THROUGH THE DAY. OVERNIGHT LOWS
COMBINED WITH SUFFICIENTLY LOW DEW POINTS COULD EASILY RESULT IN
SNOW MIXED IN WITH THE RAIN SHOWERS THROUGH ABOUT MID MORNING. NO
ACCUMULATION EXPECTED. A WARM FRONT HAS ENTERED THE WESTERN GULF
AND WILL TRACK TO THE EAST THROUGH THE SHORT TERM FORECAST
PERIOD. PRECIPITATION ASSOCIATED WITH THE FRONT SHOULD BE JUST
OFF THE OUTER COAST BY THURSDAY MORNING. NO SIGNIFICANT WARMING
ASSOCIATED WITH THE WARM SECTOR OVER SOUTHEAST ALASKA UNTIL THE
EXTENDED RANGE FORECAST PERIOD BEGINS, BUT THE APPROACHING FRONT
WILL STABILIZE THE ATMOSPHERE AHEAD OF IT.

 WITH THE LOW NOW INLAND AND HEADED TOWARDS CANADA, A RIDGE WILL
BUILD IN QUICKLY OVER THE PANHANDLE TODAY. MODELS HAVE BACKED OFF
ON THE STRENGTH OF THE SOUTHERLY PRESSURE GRADIENT, BUT STILL
SUPPORT A FULL SMALL CRAFT OVER LYNN CANAL AND STRONG WINDS OVER
SKAGWAY FOR LATER TODAY AND INTO THE EVENING. EXPECT WINDS TO
CONTINUE TO RISE EARLY IN THE EXTENDED RANGE FORECAST PERIOD.
ALSO HAVE SMALL CRAFT ADVISORY FOR CLARENCE STRAIT AND SUMNER
STRAIT TONIGHT. SMALL CRAFT WINDS OVER THE NORTHERN COASTAL
MARINE ZONES WITH A GALE WEST OF ICY BAY LATE TONIGHT IN ADVANCE
OF THE FRONT.

 USED A BLEND OF NAM AND ECMWF FOR PRESSURE AND WIND. BLENDED
GEM, SREF, AND NAM FOR POP AND QPF. TEMPS ADJUSTED WITH BIA
CORRECTED SREF. CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...THE OVERALL WEATHER PATTERN REMAINS TO BE IN GOOD
AGREEMENT FROM THE PAST FEW DAYS WITH GOOD MODEL AGREEMENT INTO
THE WEEKEND BUT THEN THEY BEGIN TO DIVERGE INTO EARLY NEXT WEEK.
A WET AND ACTIVE END OF THE WEEK CONTINUES TO BE IN STORE FOR THE
FORECAST AREA WITH HEAVY RAIN AND WINDY CONDITIONS STARTING
THURSDAY AS A FRONT STALLS OVER THE NORTHEAST GULF WITH DEVELOPING
WAVES ROLLING NORTH OUT OF THE NORTH PACIFIC ALONG THE FRONT
THROUGH SAT. THEN THERE MAYBE A BREAK IN THE WET WEATHER FOR A
NORMALLY DRY PERIOD OF THE YEAR EARLY NEXT WEEK. THERE IS ABOUT
AVERAGE TO ABOVE AVERAGE FORECASTER CONFIDENCE THROUGH THE
WEEKEND. CONTINUED TO USE A BLEND OF THE GFS/EC THROUGH THE MID
RANGE THEN HPC FROM SUNDAY THROUGH TUE.

AT THE START OF THE LONG TERM PERIOD(THURSDAY) A UPPER LEVEL LOW
WILL POSITION ITS SELF OVER THE AK PENN WITH A UPPER RIDGE OVER
THE PANHANDLE. THE UPPER LOW WILL DIG INTO THE NORTH PACIFIC
THROUGH THURSDAY NIGHT AND INCREASE THE LONG FETCH FROM THE
SUBTROPICAL PACIFIC. THIS WILL INCREASE THE MOISTURE TRANSPORT WITH
DEEP SW FLOW AND SLAM INTO THE PANHANDLE FRIDAY AND SATURDAY. A
SURFACE LOW OVER THE AK PENN THURSDAY WILL SEND A WARM FRONT OVER
THE EASTERN GULF THURSDAY AND A STRONG DEVELOPING WAVE WILL ROLL
NORTH ALONG THE FRONT AND INTO THE NE GULF FRIDAY NIGHT. WAS DOES
ALL THIS MEAN...SMALL CRAFT WINDS OVER THE GULF THURSDAY WILL
INCREASE TO GALES BY THURSDAY NIGHT AND PERSIST INTO SAT BEFORE
DIMINISHING TO 20KT BY SAT NIGHT. SEAS WILL BUILD TO BE NEAR 20 FT
BY FRIDAY BUT SLOWLY SUBSIDE THROUGH THE WEEKEND. THE WINDS OVER
THE INNER CHANNELS WILL ALSO BE ON THE WINDY SIDE AS A SURFACE
RIDGE OVER THE INNER CHANNELS WILL PERSIST AND SHARPEN UP THURSDAY
AND THEN AGAIN ON FRIDAY. THIS WILL INCREASE THE PRESSURE GRADIENT
OVER THE INNER CHANNELS AND PRODUCE SMALL CRAFTS OVER MOST OF THE
AREA WITH GALES OVER NORTHERN LYNN FROM THURSDAY NIGHT THROUGH
SAT. OVER LAND WINDS WILL ALSO BE ON THE GUSTY SIDE THROUGH THE
END OF THE WEEK INTO THE WEEKEND WITH THE STRONGEST OVER THE
EASTERN GULF COAST AND OVER NORTHERN LYNN WITH GUSTS TO 40-45MPH.

AS MENTIONED ABOVE...A LONG SW DEEP FETCH OF MOISTURE WILL SET UP AND
SLAM INTO THE PANHANDLE AS THE WARM FRONT MOVES OVER THE AREA
THURSDAY NIGHT/FRIDAY AND THEN AGAIN ON SAT AS THE WAVE MOVES
NORTH ALONG THE STALLED FRONT. THESE FRONTS AND STRONG MOISTURE
TRANSPORT WILL PRODUCE HEAVY RAIN OVER THE NE GULF COAST AREAS
ALONG WITH SOME AREAS OVER THE CENTRAL PANHANDLE. AMOUNTS WILL BE
HIGHEST NEAR PAYA WITH AROUND 5-7 INCHES FROM THURSDAY-SAT. OTHER
PLACES OVER THE CENTRAL AREAS WILL SEE 1 TO 4 INCHES WITH FREEZING
LEVELS RANGING FROM 2000 TO 3000 FEET. THERE WILL BE SIGNIFICANT
RISES IN LOCAL SMALL STREAMS AND A CONTINUED RISING WATER LEVELS
ON LARGER RIVERS DUE TO SNOW MELT ALONG WITH RAIN RUNOFF. ATTM DO
NOT EXPECT ANY FLOODING BUT WITH A PERSIST MODERATE TO HEAVY RAIN
THERE MAYBE SOME STREAMS THAT MAY GET CLOSE TO BANKFULL. LATER
SHIFTS SHOULD CONTINUE TO MONITOR THE SITUATION AND RAIN AMOUNTS
AND RATES.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH THIS EVENING
     FOR AKZ018.
MARINE...GALE WARNING FOR PKZ052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-035-036-041-042-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043.

&&

FRITSCH/ABJ