Storm Warning 42, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
341 PM AKST FRI DEC 12 2014

.SHORT TERM...QUIETER DAY ACROSS THE PANHANDLE AS THE REMAINS OF
YESTERDAY'S SYSTEM TREKS INTO CANADA. WE ARE LEFT WITH SHOWERS
MOSTLY OF THE RAIN VARIETY AS TEMPS MOST PLACES STAY IN THE MID
30S TO MID 40S AND SOME PATCHY FOG. THE FOG THAT IS IN THE
PANHANDLE IS NOT AS DENSE OR AS PERSISTENT AS IT HAS BEEN THE LAST
FEW DAYS. ANGOON WAS THE ONLY PLACE THIS MORNING THAT HAD
PERSISTENT VISIBILITIES BELOW 1 MILE AND EVEN THEN IT ONLY LASTED
UNTIL NOON.

FOR TONIGHT INTO TOMORROW SHOWERS WILL CONTINUE, HOWEVER THE
NORTHERN PANHANDLE WILL RECEIVE MORE FREQUENT AND INTENSE SHOWERS
TONIGHT AS A UPPER TROUGH MOVES THROUGH FROM THE WEST. THE TROUGH
IS CURRENTLY ORIENTED FROM AROUND CAPE SUCKLING SOUTHEASTWARD AND
IS CLEARLY VISIBLE ON SATELLITE IMAGES DUE TO THE COLDER CLOUD
TOPS OF THE MORE INTENSE SHOWERS ASSOCIATED WITH IT. THE QUESTION
MARK TONIGHT WILL BE PRECIP TYPE FOR THE NORTHERN PANHANDLE
TONIGHT AS THAT TROUGH MOVES THROUGH. THERE IS SOME SLIGHTLY
COOLER AIR BEING DRAGGED ACROSS THE GULF BY IT, BUT 850 MB TEMPS
ONLY GET DOWN TO -4 OR -5 DEGREES C ACROSS THE PANHANDLE AFTER THE
TROUGH MOVES THROUGH. THAT IS VERY MARGINAL FOR ANY SNOW AT SEA
LEVEL ESPECIALLY WITH SOUTHERLY WINDS ACROSS THE INNER CHANNELS
AND SURFACE TEMPS IN THE MID 30S. MOS PRECIP TYPE FORECASTS KEEP
JUNEAU, GUSTAVUS, AND HOONAH SOLIDLY IN RAIN INTO TOMORROW (CAN
NOT QUITE RULE OUT SNOW MIXING IN AT TIMES IN THE MENDENHALL
VALLEY TONIGHT THOUGH) WHILE YAKUTAT, HAINES AND SKAGWAY COULD SEE
A MIX OR STRAIT SNOW AT TIMES TONIGHT. AS FOR ACCUMULATIONS HAINES
AND KLONDIKE HIGHWAYS HAVE THE BEST CHANCE OF ANY ACCUMULATION
WITH UP TO 2 INCHES EXPECTED OVERNIGHT. OF SEA LEVEL LOCATIONS
HAINES MAY SEE UP TO AN INCH AS THEY KEEP THEIR NORTHWEST WIND.
SKAGWAY AND YAKUTAT WILL BE HARDER TO ACCUMULATE AS TEMPS STAY AT
OR ABOVE FREEZING OVERNIGHT AND SKAGWAY KEEPS A SOUTH WIND. THESE
AREAS MAY NOT SEE ANY ACCUMULATION OR A SLUSHY HALF INCH. INTO
TOMORROW, SHOWERS DIMINISH AS THE UPPER TROUGH MOVES INTO CANADA.

AS FOR WINDS MAIN CONCERN IS FOR THE INCREASING WINDS ACROSS THE
GULF TOMORROW AS A NEW FRONT STARTS TO MAKES ITSELF KNOWN. RECENT
FORECAST TRENDS HAVE BACKED OFF ON HOW FAST THE WINDS COME UP BY
ABOUT 6 HOURS OVER THE PREVIOUS FORECAST. STILL THE OFFSHORE AREA
WILL BE SOLIDLY IN GALE FORCE SE WINDS BY NOON SAT WITH THE
NORTHERN GULF APPROACHING MIN GALE BY LATE SAT AFTERNOON. THE
PANHANDLE ITSELF WILL LARGELY STAY OUT OF THE WINDS THROUGH SAT
BUT SOME BREEZY CONDITIONS WILL BE SHOWING UP IN THE SOUTHERN
PANHANDLE BY SAT AFTERNOON AS PRE-FRONTAL PRESSURE GRADIENTS BEGIN
TO TIGHTEN UP. AS FOR THE INNER CHANNELS WITH LARGELY EAST-WEST
GRADIENTS THE NORTH-SOUTH CHANNELS WILL FEATURE 20 KT OR LESS OF
WINDS WHILE THE EAST-WEST CHANNELS WILL HAVE WINDS INCREASING TO
25 OR 30 KT BY SAT AFTERNOON.

SHORT RANGE MODELS WERE IN GOOD AGREEMENT OVERALL TODAY. SOME
MINOR MODEL DIFFERENCES NOTED IN PRESSURE GRADIENTS AND THE
PLACEMENT OF THE LOW IN THE NW GULF. DECIDED ON USING THE NAM WITH
SOME ECMWF OVERALL AS BOTH DID REASONABLY WELL ON INITIALIZING THE
CURRENT FEATURES OVER THE AREA.

.LONG TERM...985 MB LOW AND FRONTAL SYSTEM MOVES INTO THE CENTRAL
GULF BY SAT NIGHT AND MODELS HAVE 70+ KTS AT 850MB OUT OF THE
SOUTHEAST BY EARLY SUNDAY MORNING OVER THE OFFSHORE WATERS. GRADIENTS
ENHANCED BY THE COLD AIR IN PLACE OVER THE ELEVATED INTERIOR. HAVE
WIDESPREAD GALES TO ABOUT 45 KTS AND A BIT MORE UP ON THE
NORTHWEST BARRIER JET END. GRADIENT IS NOT FAVORABLE FOR THE N-S
CHANNELS FOR OPTIMUM WIND...BUT HAVE VARIOUS GALE WINDS FOR THE
SOUTH END AND SOME OF THE CHANNELS ORIENTED MORE NE- SW FOR
SATURDAY NIGHT +. HEAVIER RAIN IS CONCENTRATED IN THE
NORTHWEST...VICINITY OF YAKUTAT...THROUGH THE LATE WEEKEND.
SIGNIFICANT RAIN OVER THE NORTHERN HALF OF THE COAST BUT ONLY LIGHT
RAIN ELSEWHERE WITH THIS SYSTEM. MODELS HAVE THE LOW RETREATING
RAPIDLY NORTHWESTWARD LATER ON SUNDAY BUT THE TRAILING FRONT
PRODUCES PANHANDLE PRECIP THROUGH MUCH OF MONDAY. THEN THE NAM HAS
AN OUTLIER LOW SNEAKING UP TO THE SOUTHERN PANHANDLE AT 84HR AND
THE GFS SHOWS A SHORTWAVE SNEAKING UP A BIT FASTER. DID ENSEMBLE
THIS INTO THE PRESSURE FIELD BUT NOT SURE IF I BELIEVE IT. TWEAKED
THE WINDS ON DAYS 2-4 IN LOCAL AREAS AND THE ANCHORAGE BOUNDARY
BUT FOR THE MOST PART LEFT THINGS AS IS...ALSO UPDATED THE
MOISTURE AND TEMPERATURE FIELDS PER LATEST GUIDANCE FROM THE
NAM/EC/GFS. EVOLVED WITH THE EC/NAM WINDS/PRESSURE UNTIL DAY 5
THEN WPC GUIDANCE. MODEL DIFFERENCES ALOFT ARE MOSTLY MINOR UNTIL
ABOUT MONDAY NIGHT....WITH THE EC SHOWING A MORE INTENSE LOW AT
THAT POINT COMING UP FROM THE SOUTH OFF THE EAST END OF THE
EASTERN PACIFIC TROUGH...AND THE GFS SHOWING A COMPACT STRONG
SECONDARY WAVE IMPACTING THE PANHANDLE BY EARLY TUES. GEM
MEANWHILE HAS A BIT MORE AMPLITUDE IN THE TROUGH AT THAT POINT AND
DRIVES THE MAIN TROUGH ENERGY FURTHER SOUTHWARD, PUTTING US BACK
INTO AN UPPER RIDGE BUT IT IS THE OUTLIER. GENERALLY THE UPPER
LEVEL POSITIONS OF THE LONGWAVE TROUGH ARE SIMILAR THROUGH ABOUT
EARLY WED. LARGE DIFFERENCES INCREASE FROM THAT POINT ON BUT THE
GENERAL PICTURE IS CONTINUED ACTIVE EASTERN GULF WEATHER THROUGH
AT LEAST 7 DAYS. EC HAS A DEEPER, MORE CLOSED OFF L OVER THE GULF
BY THURS.

OVERALL, NO THREAT OF SIGNIFICANT SNOW AT LOW LEVELS
THROUGH THE PERIOD...CURRENTLY HANGING ONTO AN OCCASIONAL
NOCTURNAL MIX AT HYDER AND THE NORTHERN FRINGES OVER THE NEXT FEW
DAYS, BUT RAIN OTHERWISE THROUGH AT LEAST EARLY TO MID-WEEK. MODEL
CONFIDENCE IS SOMEWHAT ABOVE AVERAGE THROUGH ABOUT DAY 4 THEN
AVERAGE AFTER THAT.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041>043-052.
         SMALL CRAFT ADVISORY FOR PKZ012-021-022-033>036-051.

&&

EAL/WESLEY

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