Small Craft Advisory 709, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
423 PM AKST THU NOV 10 2011

.SHORT TERM...LOW PRESSURE SYSTEM IN THE NORTHEAST GULF WILL
CONTINUE ITS SOUTHEASTERLY TRACK MOVING OVER THE CENTRAL AK
PANHANDLE TONIGHT AND INTO BRITISH COLUMBIA BY FRIDAY MORNING.
ASSOCIATED WEATHER FRONT CURRENTLY PRODUCING MIXED PRECIPITATION
AND SOME GUSTY WINDS WILL EXIT THE REGION OVERNIGHT. YAKUTAT
PRECIP REMAINED SNOW THROUGH THE DAY WITH WARM AIR KEPT JUST TO
THE SOUTH. EXPECTING THE WARM SECTOR OF THE LOW STILL TO PUSH A
BIT FURTHER NORTH THIS EVENING SO MAY STILL SEE SOME RAIN MIXING
IN. MOST OTHER AREAS TRANSITIONED TO MOSTLY RAIN AS WINDS SHIFTED
FROM THE NORTH TO SOUTH THIS MORNING...WITH THE EXCEPTION OF
PETERSBURG WHICH RETAINED ENOUGH COLD AIR TO STAY SNOW. OVERALL
SNOW ACCUMULATION WAS LESS THAN 1 INCH. AS THE FRONT MOVES EAST
PRECIP WILL DIMINISH FROM NORTH TO SOUTH AND WINDS WILL BEGIN TO
SHIFT FROM THE SOUTH TO NORTH. RAIN WILL BEGIN TO MIX WITH SNOW
TEMPS DROP THROUGH THE EVENING AND WINDS SHIFT NORTH, BUT SINCE
THE FRONT IS MOVING ON NO REAL ACCUMULATION EXPECTED. AS ROADS
WILL BE WET THIS EVENING AND TEMPS DROPPING BELOW FREEZING WITH
CLEARING SKIES TONIGHT ROADS MAY BE ICY FOR FRIDAY MORNING.
FRIDAY ITSELF WILL SEE CLEARING SKIES THROUGH THE DAY AS HIGH
PRESSURE MOVES INTO THE YUKON AND A RIDGE BUILDS OVER THE AK
GULF. WHILE A COLD AIR MASS, WITH 850 TEMPS AROUND -6C, PUSHES
SOUTH TEMPS MAY BE STILL IN THE MID TO UPPER 30S FROM INCREASED
SOLAR HEATING. SO ALL IN ALL A NICE DAY FOR SE AK.

 MODELS WERE IN FAIR AGREEMENT TODAY WITH THE PLACEMENT OF THE
LOW AND FRONT. THE 12Z NAM WAS MORE OF AN OUTLIER PLACING THE LOW
FURTHER SOUTH BUT THE 18Z FELL MORE IN LINE. TRENDED TOWARD THE
ECMWF BUT OVERALL MADE FEW CHANGES TO THE WIND FIELDS. MAIN
ISSUES FOR THE FORECAST WERE TIMING THE WIND SHIFTS THIS EVENING,
WITH SOME LOCATIONS STARTING A BIT EARLIER THAN EXPECT, SUCH AS
SKAGWAY, AND OTHER, SUCH AS N LYNN CANAL BEING DELAYED. AS PRECIP
WILL BE DIMINISHING THROUGH THE EVENING THE RAIN TO SNOW
TRANSITION IS NOT AS MUCH OF A CONCERN DUE TO LIMITED
ACCUMULATION. FORECAST CONFIDENCE IS ABOUT AVERAGE.

&&

.LONG TERM...FIRST MAJOR FEATURE IN THE EXTENDED RANGE FORECAST
WILL BE A STRONG FRONT THAT APPROACHES THE OUTER COAST FRIDAY
NIGHT. GALE FORCE SOUTHEASTERLIES IN ADVANCE OF THE FRONT,
FOLLOWED BY SUSTAINED SOUTHWESTERLY GALES AFTER FRONTAL PASSAGE.
OVERNIGHT LOWS SHOULD BE LOW ENOUGH TO SUPPORT 2 TO 4 INCHES OF
SNOW OVERNIGHT FRIDAY AND THROUGH MUCH OF SATURDAY FROM PETERSBURG
NORTH OVER THE INTERIOR PUBLIC ZONES. WARM AIR ASSOCIATED WITHE
THE THERMAL RIDGE WILL RESULT IN RAIN MOST OTHER PLACES AND ALONG
THE OUTER COAST IN PARTICULAR. WESTERLY WINDS BEGIN TO DIMINISH BY
SUNDAY MORNING AND THEN COLD LOW LEVEL AIR ADVECTING ZONALLY
ACROSS THE GULF FROM THE BERING SEA WILL SPREAD OVER THE PANHANDLE
AND BEGIN TO SEND DAILY HIGHS AND LOWS SOUTH. AS THE UPPER LOW
DROPS SOUTHEAST ALONG THE EASTERN GULF BEGINNING MONDAY, VERY COLD
LOW LEVEL AIR WILL DESCEND SOUTH FROM THE HIGH ARCTIC. ARCTIC
FRONT LOOKS LIKE IT WILL PENETRATE AS FAR SOUTH AS ANGOON AND
PETERSBURG BY LATE NEXT WEEK AND INTO THE FOLLOWING WEEKEND. NOT A
LOT OF POP IN THE FORECAST DURING THIS TIME SINCE LOW LEVEL FLOW
WILL BE EASTERLY FROM THE VERY COLD AND DRY CANADIAN INTERIOR AND
MAY GET WINDY IN LOCATIONS SUSCEPTIBLE TO STRONG OUTFLOW WINDS
FROM THE NORTH AND NORTHEAST.

USED NAM AND GFS EARLY ON, THEN A GFS/HPC BLEND. FORECAST
CONFIDENCE IS ONLY AVERAGE DUE TO A SUBTLE CHANGE IN SNOW LEVELS
FRIDAY NIGHT INTO SATURDAY WHICH HAVE RESULTED IN A SIGNIFICANT
CHANGE IN THE SNOW FORECAST FOR THAT TIME FRAME.

.CLIMATE...THE LA NINA TREND FOR WINTER OVER SOUTHEAST ALASKA
APPEARS TO BE BEGINNING TO EXERT ITSELF IN THE FORM OF COLDER THAN
NORMAL TEMPERATURES. CLIMATE PREDICTION CENTER 1-WEEK, 2-WEEK, AND
WINTER SEASON TEMPERATURE OUTLOOKS ALL REMAIN TILTED IN FAVOUR OF COLDER
THAN NORMAL TEMPERATURES. JUST HOW MUCH COLDER THAN NORMAL REMAINS
TO BE SEEN. SEA SURFACE TEMPERATURES IN THE EQUATORIAL PACIFIC
OCEAN ARE CLEARLY BELOW NORMAL, HOWEVER THERE HAS BEEN VERY LITTLE
CHANGE OVER THE PAST 3 WEEKS. THE CURRENT NINO 3.4 VALUE IS -0.9
DEGREES C AND THE CURRENT ONI IS -0.4 DEGREES C. UPPER LEVEL JET
HAS BEEN FAIRLY ZONAL OVER THE SAME TIME FRAME, WHICH IS MORE OF
AN EL NINO PATTERN HOWEVER, THE JET IS WEAKER AND FARTHER NORTH
WHICH ARE TWO LA NINA CHARACTERISTICS. CURRENT MJO ACTIVITY IS
CENTERED OVER THE MARITIME CONTINENT AND IS FAIRLY BROAD IN ITS
AREAL COVERAGE, HOWEVER OTHER FEATURES USED TO MONITOR THE
EVOLUTION OF THE MJO SUGGEST THIS CURRENT EVENT IS WEAK AND WILL
REMAIN WEAK AS IT MOVES ACROSS THE WESTERN PACIFIC. AT THIS TIME,
NO MJO IMPACTS TO SOUTHEAST ALASKA ARE EXPECTED IN THE EXTENDED
RANGE FORECAST PERIOD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041>043-052.
         SMALL CRAFT ADVISORY FOR PKZ012-033>036-051.

&&

PRB/FRITSCH