Small Craft Advisory 608, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
210 PM AKDT MON OCT 12 2009

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
CLOUD FREE WITH THE EXCEPTION TO THE PAYA AREA AS THERE ARE SOME
LOW CLOUDS HANGING AROUND. THESES CLOUDS WILL SLOWLY DISSIPATE
AND PUSH TO THE WEST WITH THE INCREASING OFFSHORE FLOW.

THE UPPER HIGH OVER THE INTERIOR OF THE STATE WILL PERSIST
THROUGH THE SHORT TERM PERIOD WHILE THE UPPER LOW OVER EASTERN BC
WILL DRIFT WEST TO BE OVER PORTLAND CANAL TONIGHT AND IN THE SE
GULF BY TUESDAY AFTERNOON. AT THE SURFACE THE HIGH PRESSURE OVER
BC WILL CONTINUE TO BUILD WEST AGAINST THE COAST MOUNTAINS THROUGH
TONIGHT. THE PRESSURE GRADIENT WILL TIGHTEN SIGNIFICANTLY THROUGH
TUESDAY AS LOW PRESSURE LIFTS OUT OF THE EASTERN PACIFIC TO BE
JUST SOUTH OF THE QUEEN CHARLOTTES BY TUE AFTERNOON.

THE CONSTANT OFFSHORE FLOW WILL KEEP MOST CLOUDS AWAY FROM THE
PANHANDLE. THE SOUTHERN AREAS MAY SEE SOME CLOUDS MOVE OVER THE
AREA EARLY TUESDAY MORNING FROM THE SURFACE LOW BUT THEY WILL WILL
NOT LAST LONG AND DISSIPATE THROUGH THE AFTERNOON. CLEAR SKIES
TONIGHT WILL RESULT IN RADIATIVE COOLING ALONG WITH COLD 850MB
TEMPS OF -5 TO -10C ADVECTING IN FROM THE EAST. THIS WILL CAUSE
TEMPS TO FALL INTO THE MID 30 TO MID 20 DEPENDING ON LOCATION. THE
COLDEST TEMPS WILL BE IN WIND SHELTERED AREAS AND AWAY FROM THE
OCEAN. SO WITH THAT SAID THERE WILL BE AREAS OF FROST AGAIN
TONIGHT OVER MOST AREAS EXCEPT FOR THE COASTAL AREAS OF ZONES 22
AND 23. SO WITH THAT SAID HAVE ISSUED A FROST ADVY FOR ZONE 27 AS
PAKW AND OTHER AREAS OVER POW WILL SEE TEMPS IN THE LOWER 30S AND
A FREEZE WARNING FOR ZONES 19,24,26 AS THEY WILL SEE TEMPS IN THE
UPPER 20S. IN THE WIND SHELTERED AREAS FOG WILL FORM AND MAY
REDUCE VISIBILITIES TO LESS THAN 1 MILES A TIMES ESPECIALLY NEAR
PAPG, PAGN AND NEAR CROSS SOUND.

AREAS ADJACENT TO THE COAST MOUNTAINS WILL SEE THE WINDS INCREASE
SIGNIFICANTLY ALONG WITH WINDS IN NORTHERN LYNN CANAL AND IN
EAST/WEST MARINE CHANNELS. THE HIGH PRESSURE OVER CANADA WILL
CONTINUE TO STRENGTHEN AND INCREASE THE PRESSURE GRADIENT. THE
GALE WARNING IN LYNN CANAL WILL CONTINUE THROUGH THE SHORT TERM
ALONG WITH THE SMALL CRAFT IN ICY AND CROSS SOUND. THE WINDS WILL
INCREASE OVER THE REST OF THE MARINE WATERS THROUGH TUES TO 20KT
AND MIN SMALL CRAFT. THE LARGE PRESSURE GRADIENT IS ALSO PRODUCING
VERY STRONG WIND GUSTS FROM INTERIOR PASSES TO 40KT AND THESE WILL
CONTINUE THROUGH TONIGHT AND INCREASE THROUGH TUES AS THE CROSS
BARRIER FLOW STRENGTHENS. THE CROSS BARRIER FLOW ALONG WITH THE
PRESSURE GRADIENT IS PRODUCING STRONG GUSTY WINDS OVER THE LAND
AREAS WITH BREEZY CONDITIONS OVER ZONES 18...26 AND 28. THESE
WINDS WILL CONTINUE THROUGH TUES. MOUNTAIN WAVE WINDS NEAR
DOWNTOWN JUNEAU AND DOUGLAS ARE VERY STRONG AND THERE HAVE BEEN
GUSTS AS HIGH AS 50 MPH SO FAR TODAY. THESE GUSTS WILL
INCREASE THROUGH TUES AFTERNOON AS THE PRESSURE GRADIENT INCREASES
ALONG WITH THE CROSS BARRIER FLOW. THE CROSS BARRIER FLOW WILL
INCREASE TO AROUND 70KT AT MOUNTAIN TOP SO THERE IS A CHANCE THAT
WIND GUSTS COULD EXCEED 60 MPH AT SEA LEVEL TONIGHT INTO TUES. WILL
NEED TO KEEP A CLOSE EYE ON THE SITUATION.

&&

.LONG TERM...WIND EVENT WILL EXTEND INTO THE LONG RANGE FORECAST
PERIOD AND WILL LIKELY ENCOMPASS THE HAINES ZONE. ALMOST CERTAINLY
SKAGWAY WILL SEE ADVISORY LEVEL WINDS AS WELL BUT THEY ARE NOT
FORECAST FOR THAT ZONE UNTIL AFTER THE BEGINNING OF THE LONG RANGE
FORECAST PERIOD...HENCE NO HEADLINE OR NPW FOR THEM YET. CANNOT
RULE OUT A HIGH WIND WARNING FOR ZONE 25 UP THE TAKU INLET OR ZONE
29...BUT DO NOT HAVE ENOUGH CONFIDENCE IN THAT TO ISSUE A THIRD
PERIOD WARNING.

GALES OVER THE NORTHERN INNER CHANNELS THROUGH WEDNESDAY NIGHT AS
WELL AS STEPHENS PASSAGE...SUMNER AND CLARENCE STRAIT THROUGH WEDNESDAY.
STRONG SMALL CRAFT CONDITIONS ELSEWHERE. SEAS ON CLARENCE COULD BE
PARTICULARLY WICKED LATE WEDNESDAY NIGHT AS WINDS ARE FORECAST TO
SHIFT FROM NORTHWEST TO SOUTHEAST WITH LITTLE CHANGE IN WIND
SPEED...SO SEAS WILL BE EXTREMELY CHOPPY. STORM FORCE GUSTS OR
HIGHER ARE FORECAST OUT OF INTERIOR PASSES INTO FREDERICK SOUND...STEPHENS
PASSAGE...AND CLARENCE STRAIT. MARINER ARE ADVISED TO EXERCISE
EXTREME CAUTION WHEN TRANSITING THESE AREAS.

USED NAM AS PRIMARY GUIDANCE THROUGH THURSDAY AFTERNOON. MAJOR
DIFFERENCES IN THE ECMWF OVERNIGHT PROMPTED A SHIFT IN PREFERENCE
FOR THE GFS WRT PRESSURE AND WIND THEREAFTER. BLENDED IN A
SIGNIFICANT AMOUNT OF ECMWF FOR THE POP FIELD. THAT SAID...NOT A
LOT OF POP IN THE FORECAST UNTIL AFTER OVERNIGHT LOWS COME BACK UP
TO MORE SEASONAL TEMPERATURES IN THE SECOND HALF OF THE WEEK...SO
NO SNOW IN THE FORECAST YET.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HARD FREEZE WARNING FROM 2 AM TO 9 AM AKDT TUESDAY FOR AKZ019-
 	 024-026.
	 FROST ADVISORY FROM 2 AM TO 9 AM AKDT TUESDAY FOR AKZ027.
	 WIND ADVISORY UNTIL 6 AM AKDT WEDNESDAY FOR AKZ025-029.
MARINE...GALE WARNING FOR PKZ012-041.
	 SMALL CRAFT ADVISORY FOR PKZ013-021-022-031-034>036-042-043.
	 SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-052.

&&

ABJ/FRITSCH