Small Craft Advisory 567, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
359 PM AKDT TUE OCT 2 2012

.SHORT TERM...WELL DEVELOPED BAROCLINIC LEAF CLOUD ASSOCIATED
WITH AN APPROACHING WARM FRONT IS SPREADING EAST OVER THE
PANHANDLE THIS AFTERNOON. A THIN HIGH OVERCAST COVERS MOST
LOCATIONS AS OF EARLY THIS AFTERNOON. PRECIPITATION FROM THIS
FRONT NOW VISIBLE ON THE MIDDLETON ISLAND RADAR, BUT CANNOT SEE
THE LEADING EDGE YET ON THE BIORKA ISLAND RADAR. COOLER LOW LEVEL
AIRMASS IN PLACE WILL RESULT IN OVERNIGHT LOWS A LITTLE WARMER
THAN LAST NIGHT, BUT AN OVERNIGHT FREEZE STILL IS POSSIBLE ALONG
THE HAINES AND KLONDIKE HIGHWAYS AS WELL AS WIND SHELTERED
LOCATIONS NORTH OF JUNEAU. BELIEVE INCREASING CLOUD COVER WILL
TRAP WHAT LITTLE DAYTIME HEATING THERE WAS AND KEEP OTHER
LOCATIONS RELIABLY ABOVE FREEZING.

 THINK THE PRECIP WILL ARRIVE ALONG THE OUTER COAST IN ZONE
17 WEST OF ICY BAY LATER THIS AFTERNOON AND SPREAD EAST AND SOUTH
OVERNIGHT. HAVE DRAWN THE LIKELY POP LINE AS FAR SOUTH AS CAPE
OMMANEY BY TOMORROW MORNING. HAVE CHANCE POPS OVER THE HAINES
HIGHWAY FOR LATE TONIGHT AND IF PRECIP DOES MAKE IT THAT FAR
INLAND TONIGHT, THERE IS A GOOD CHANCE THE HIGHWAY WILL SEE SNOW
TONIGHT BUT ONLY EXPECT A TRACE AT MOST. FOR TOMORROW, GREATEST
CHANCE FOR PRECIP WILL BE ALONG THE OUTER COAST AND HAVE LIMITED
THE LIKELY POP LINE TO LOCATIONS WEST OF CHATHAM STRAIT TOMORROW
MORNING, AND WEST OF CLARENCE STRAIT FOR THE AFTERNOON.

 HAVE SOUTHEASTERLY GALE FORCE WINDS IN OFFSHORE MARINE ZONE
310 FOR TONIGHT THAT WILL SPREAD INTO COASTAL ZONE 52 BEFORE
TOMORROW MORNING. WILL ALSO SEE EASTERLY SMALL CRAFT WINDS OUT OF
ICY STRAIT AND CROSS SOUND IN RESPONSE TO THE APPROACHING FRONT.
SMALL CRAFT ADVISORIES FOR SOUTHERN CHATHAM STRAIT AND WESTERN
PORTIONS OF SUMNER STRAIT FOR TOMORROW AFTERNOON AS WELL.

 USED NAM FOR UPDATES TO THE SHORT TERM FORECAST PERIOD PRESSURE
AND WIND. BLENDED NAM AND ECMWF FOR POP AND QPF. TEMPERATURES
ADJUSTED USING GFS40 FORECAST CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...THE LONG TERM MODELS LOOK TO BE IN GOOD AGREEMENT
THROUGH THE WEEKEND WITH A LARGE UPPER/SURFACE HIGH BUILDING FROM
THE SOUTH TO THE NORTH. ALL MODELS ALONG WITH ENSEMBLE MEMBERS ARE
SHOWING THE SAME STORY SO THERE WAS OVERALL MINOR CHANGES TO THE
FORECAST THROUGH THE MID RANGE BUT DID INCREASE POPS ON WED NIGHT
INTO THURSDAY. IN THE EXTENDED PERIODS REFRESHED THE FORECAST WITH THE
LATEST HPC GUIDANCE WHICH KEPT THE PANHANDLE ON THE DRY SIDE INTO
EARLY NEXT WEEK AS THE UPPER HIGH OVER THE GULF KEEPS ANY WEATHER
SYSTEM AWAY FROM SE AK. USED MAINLY THE NAM12 THROUGH 84HRS AND
THEN HPC THROUGH DAY 8. THERE IS ABOUT AVERAGE FORECAST CONFIDENCE
THROUGH THE THIS WEEKEND.

AT THE START OF THE LONG TERM PERIOD A SURFACE TROF WILL BE OVER
THE EASTERN GULF THAT WILL SLIDE INTO THE NORTHERN GULF THROUGH
WED NIGHT AND PERSIST THROUGH THURSDAY. THIS TROF WILL KEEP 20 TO
25 KT FROM ESE OVER THE THAT AREA WHILE THE REST OF THE EASTERN
GULF SEES 10 TO 15 KT. THERE WILL SOME STRONG WINDS TO SMALL CRAFT
WINDS NEAR CROSS SOUND BUT AS THE TROF LIFTS NORTH THE WINDS WILL
RELAX. THIS TROF WILL INCREASE THE THREAT OF PRECIP FOR THE
NORTHERN GULF COAST WED NIGHT TO CAT WHILE THE NORTHERN HALF OF
THE PANHANDLE WILL SEE RAIN LIKELY WED NIGHT THROUGH THURSDAY.
THIS WAS A CHANGE FROM PREVIOUS SHIFT AS WITH THE UPPER RIDGE
BUILDING NORTHWARD AND DEEP ONSHORE FLOW ALONG WITH WARM AIR
ADVECTION THIS WILL PRODUCE ENOUGH LIFT TO ALLOW LIGHT RAIN TO BE
LIKELY THROUGH THURSDAY AFTERNOON. AS THE UPPER HIGH CONTINUES TO
STRENGTHEN AND THE SURFACE TROF WEAKENS LATE THURSDAY NIGHT INTO
FRIDAY THE THREAT OF LIGHT RAIN WILL DIMINISH AND THE SOUTHERN
HALF WILL SEE SOME LARGE BREAKS IN THE CLOUD COVER TO BE PARTLY
CLOUDY.

THIS UPPER HIGH IS PUSHING UP VERY WARM TEMPS ALOFT AND WITH THIS
TIME OF YEAR IT COULD PRODUCE WIDESPREAD FOG OVER THE INNER
CHANNELS STARTING FRIDAY NIGHT. THERE WILL ALSO BE AN AREA OF LOW
SEA STRATUS THAT WILL FORM UNDER THE HIGH AND LIFT OVER THE
EASTERN GULF. THERE IS ABOUT AVERAGE FORECASTER CONFIDENCE ON THIS
AND LATER SHIFTS SHOULD KEEP AN EYE ON THIS.

WINDS FOR THE MOST PART WILL BE LESS THAN 15 KT BUT THE WIND
DIRECTION WILL BE TRICKY WITH A WEAK PRESSURE GRADIENT. FOR THE
MOST PART THEY WILL BE FROM THE SOUTH BUT THERE WILL SOME AREA
OVER THE CENTRAL AND SOUTHERN AREAS THAT WILL SEE NORTHWEST WINDS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
         SMALL CRAFT ADVISORY FOR PKZ021-022-033-035-041>043-051.

&&

FRITSCH/ABJ