Small Craft Advisory 655, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
342 PM AKST TUE NOV 6 2012

.SHORT TERM...SATELLITE IMAGES THIS MORNING ARE SHOWING A
DEVELOPING LOW WITH A DECENT BAROCLINIC LEAF JUST SOUTHWEST OF
BARANOF ISLAND. THIS LOW IS SPREADING RAIN AND CLOUDS OVER MUCH
OF THE PANHANDLE. THE EXCEPTION IS YAKUTAT AS THEY ARE STILL
NORTH OF THE MAIN CLOUD SHIELD UNDER MOSTLY CLEAR SKIES. THE SEMI
VIGOROUS FRONTAL BAND THAT THE LOW IS PRODUCING IS ALSO BRINGING
SOME GUSTY WINDS TO THE SOUTHERN PANHANDLE THIS MORNING WITH
HYDABURG REPORTING GUSTS UP TO 32 KT AND LIGHTER GUSTS IN OTHER
PARTS OF THE SOUTH.

SHORT TERM FORECAST BECOMES INCREASINGLY MORE COMPLEX THROUGH THE
PERIOD AS WE NOT ONLY HAVE THE LOW OFF OF BARANOF ISLAND TO WORRY
ABOUT BUT A BUILDING HIGH OVER THE YUKON AS WELL. THE EASTERN GULF
LOW WILL STALL OFF OF BARANOF ISLAND TONIGHT AS THE UPPER TROUGH
THAT HAS BEEN PROVIDING THE SOUTHERLY FLOW ALOFT TO MOVE IT NORTH
MOVES EAST. THIS WILL ALSO CAUSE THE NORTHERLY STEERING FLOW ON
THE BACK SIDE OF THE TROUGH TO INCREASE ABOVE THE WESTERN GULF LOW
AND START MOVING IT SOUTH AND EAST. WITH THE EASTERN GULF LOW NOT
MOVING MUCH OF ANYWHERE ANYTIME SOON SHOWERS WILL CONTINUE OVER
THE PANHANDLE FOR MOST OF THE NIGHT AND INTO EARLY TOMORROW.

MEANWHILE A STRONG COLD HIGH PRESSURE SYSTEM WILL BE BUILDING IN
THE YUKON OVERNIGHT AND WILL START INCREASING THE OFFSHORE AND
OUTFLOW WINDS ACROSS THE NORTHERN PANHANDLE. THE MOST AFFECTED
AREAS WILL BE THE PASSES EAST OF YAKUTAT, DISENCHANTMENT BAY, LYNN
CANAL, AND SKAGWAY. FORECAST SOUNDINGS FOR WHITEHORSE SHOW THAT
THE COLD AIR WILL BE DEEP ENOUGH TO SPILL OVER THE MOUNTAIN PASSES
SO WINDS WILL BE STRONG WITH THE COLD AIR DRAINAGE SUPPORTING IT.
HAVE HOISTED A GALE WARNING FOR NORTHERN LYNN AND A STRONG WIND
HEADLINE FOR SKAGWAY FOR TONIGHT AND TOMORROW. SMALL CRAFT
ADVISORIES HAVE ALSO BEEN HOISTED FOR MOST OF THE NORTHERN INNER
CHANNELS TOMORROW AS WELL. WITH THE COLD AIR THAT WILL BE DRAINING
INTO THE NORTHERN PANHANDLE AND THE WIND THE POSSIBILITY FOR
FREEZING SPRAY IN LYNN CANAL AND GLACIER BAY BECOMES A
POSSIBILITY. CONDITIONS WILL BE THERE FOR SOME MODERATE FREEZING
SPRAY IN NORTHERN LYNN FOR LATE TONIGHT AND TOMORROW WHILE GLACIER
BAY SHOULD ONLY SEE SOME LATE TONIGHT AND EARLY TOMORROW.
TEMPERATURES SHOULD NOT BE COLD ENOUGH AND WINDS SHOULD NOT BE
HIGH ENOUGH FOR HEAVY FREEZING SPRAY YET.

THE INTERACTION BETWEEN THE AIR-MASSES AROUND THE EASTERN GULF
LOW AND THE YUKON HIGH WILL MAKE PRECIP TYPE A BIT CHALLENGING.
WITH THE SHOWERS STILL AROUND THE AREA BUT THE COLD AIR BEGINNING
TO DRAIN INTO THE NORTH, SOME OF THOSE RAIN SHOWERS MAY MIX WITH
OR BECOME SNOW SHOWERS LATE TONIGHT AND EARLY TOMORROW
PARTICULARLY IN THE NORTH. SNOW ACCUMULATION SHOULD BE LIGHT AS
SHOWERS WILL BE SLOWLY DIMINISHING FROM NORTH TO SOUTH TOMORROW AS
THE HIGH BECOMES MORE DOMINANT AND THE GENERAL AREA OF LOW
PRESSURE IN THE GULF SLIPS SE TO BECOMING A INVERTED TROUGH OVER
THE AREA BY WED AFTERNOON.

SHORT RANGE MODELS WERE IN DECENT AGREEMENT THROUGH THE PERIOD.
NAM SEEMED TO BE A BIT OF AN OUTLIER WITH HOW IT INTERPRETED THE
LOW JUST OFF OF BARANOF ISLAND. IT INITIALIZED THE LOW A BIT TOO
FAR TO THE EAST COMPARED TO SATELLITE IMAGES, AND THE OTHER GLOBAL
MODELS. THE NAM ALSO KEPT THE LOW FARTHER EAST THEN THE OTHER
MODELS AS THE LOW STALLS AND FINALLY DRIFTS SE BY TOMORROW
AFTERNOON. DECIDED ON USING THE GFS AND ECMWF FOR UPDATES TONIGHT
THEN USED MORE ECMWF FOR TOMORROW AS THE YUKON HIGH BEGINS TO
DOMINATE. FORECAST CONFIDENCE IS A LITTLE ABOVE AVERAGE.

&&

.LONG TERM...THE START OF THE MID TERM FORECAST PACKAGE STARTING
WEDNESDAY NIGHT INTO FRIDAY THE MODEL SOLUTIONS SEEMED TO HAVE
GENERALLY QUITE SIMILAR TRACKING OF THE FIRST LOW WITH A BUILDING
RIDGE OVER THE GULF AND INTERIOR AND NORTHWEST CANADA. THERE IS A
COLD POOL OF AIR OVER THE INTERIOR AND NORTHWEST CANADA. A TIGHT
PRESSURE GRADIENT WILL HAVE STRONG NORTH AND OUTFLOW WINDS ACROSS
THE NORTHERN HALF OF THE PANHANDLE... EVENING KICKING UPS SOME
PERIODS OF FREEZING SPRAY IN THE LYNN CANAL AND NORTHERN PORTIONS
OF GLACIER BAY.

THE RIDGE OVER THE GULF GETS MOVED EASTWARD FROM THE LOW OVER THE
EASTERN ALEUTIANS TO BRISTOL BAY BY THE EARLY FRIDAY. WITH SLOW
MOVING STALLED WEATHER FRONT ACROSS THE GULF INTO SATURDAY. LOOKS
LIKE IT MAY NOT IMPACT SOUTHEAST ALASKA SIGNIFICANTLY UNTIL THE
WEEKEND. HOWEVER BY THAT TIME DIFFERENCES CREEPING INTO THE
MODEL SOLUTIONS IS MAKING THE WEEKEND INTO EARLY PART OF NEXT
WEEK HAVE MUCH LOWER CONFIDENCE. FOR THE LATE PERIODS DID ONLY
SOME MINOR ALTERATIONS TO THE WIND AND SOME TEMPERATURES WITH SOME
CHANGES TO WEATHER AS WELL. HAD BETTER CONFIDENCE FOR THE REST OF
THIS WEEK...SO ONLY SMALL CHANGES THERE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH WEDNESDAY
     AFTERNOON FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031-035-036-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041>043-052.

&&

EAL/BEZENEK