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000
FXAK67 PAJK 111446
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
546 AM AKST WED DEC 11 2013

.SHORT TERM...TODAY THROUGH THURSDAY...MESSY MORNING ACROSS THE
NORTHERN HALF OF THE PANHANDLE AS RAIN HAS CHANGED BACK TO SNOW
ALONG THE ICE STRAIT CORRIDOR WITH SNOW IN HAINES AND RAIN FARTHER
SOUTH. SOME EARLY MORNING SNOW REPORTS HAVE 1 INCH AT THE JUNEAU
WEATHER OFFICE IN THE MENDENHALL VALLEY AT 3 AM, 2 INCHES AT
JUNEAU AIRPORT AT 3 AM, AND 3 TO 4 INCHES AT THE AUKE BAY SCHOOL
BUS GARAGE AT 430 AM. WEBCAMS FROM DOWNTOWN SHOW ONLY WET SLUSHY
ROADS AT THE MOMENT. AS A RESULT THE WINTER STORM WATCHES THAT
WERE IN EFFECT FOR JUNEAU, HOONAH, GUSTAVUS, AND ELFIN COVE HAVE
BEEN UPGRADED TO A WINTER STORM WARNING FOR MOST OF TODAY THROUGH
TONIGHT AND INTO THURSDAY. A WINTER STORM WARNING CONTINUES FOR
HAINES AND HYDER WITH SNOW ALREADY FALLING THERE. A BLIZZARD
WARNING ALSO REMAINS UP FOR SKAGWAY AS SNOW IS EXPECTED TO BEGIN
THERE SOMETIME THIS MORNING AND WITH THE WINDS ALREADY OCCURRING
SOME VISIBILITIES DOWN TO A QUARTER MILE ARE EXPECTED ALONG THE
KLONDIKE HIGHWAY THROUGH THURS. UPWARDS OF 10 TO 23 INCHES OF SNOW
IS EXPECTED ACROSS THE NORTHERN PANHANDLE AND NEAR HYDER THROUGH
THURSDAY AS TWO SYSTEMS CONVERGE OVER THE AREA. THE FIRST IS THE
STORM SYSTEM FROM THE GULF THAT GAVE US THE WARM UP AND RAIN LAST
NIGHT, AND THE SECOND IS A COLD UPPER TROUGH COMING SOUTH FROM THE
YUKON. THE NORTHERN SYSTEM IS THE ONE THAT WILL EVENTUALLY WIN OUT
WITH MOST AREAS FROM ANGOON NORTHWARD SLOWLY COOLING THROUGH THE
DAY AND KEEPING THE PRECIP AS SNOW FOR THE ICE STRAIT CORRIDOR
NORTHWARD. INTO TONIGHT AND THURSDAY THE SNOW WILL CONTINUE FOR
THE NORTH WITH ANGOON AND MAYBE THE NORTHERN PART OF ZONE 26
GETTING IN ON THE ACT. DECIDED TO ISSUE A WINTER WEATHER ADVISORY
FOR ANGOON AS I THINK THEY WILL GET ENOUGH SNOW LATE TONIGHT AND
TOMORROW TO WARRANT IT. YAKUTAT, PETERSBURG AND KAKE MAY SEE SOME
SNOW TODAY THROUGH THURSDAY BUT THEY WILL EITHER BE TOO WARM OR
WILL NOT HAVE ENOUGH QPF TO GET TO ADVISORY CRITERIA.

 FOR PRECIP, A VERY NICE TROPICAL MOISTURE FEED FROM NEAR HAWAII
IS STILL AIMED RIGHT AT THE PANHANDLE FOR TODAY AND TONIGHT.
HIGHEST QPF AMOUNTS ARE EXPECTED TODAY WITH UP TO AN INCH OF
MOISTURE ACROSS PARTS OF THE PANHANDLE TODAY. QPF AMOUNTS LIGHTEN
UP TONIGHT AS THE MAIN PART OF THE MOISTURE PLUME SHIFTS EAST BUT
THE LOW IN THE GULF WILL STILL WRAP SOME OF THAT MOISTURE INTO THE
PANHANDLE TONIGHT AND THURSDAY. UP TO HALF TO THREE QUARTERS OF AN
INCH OF MOISTURE IS EXPECTED OVER THE PANHANDLE FOR TONIGHT AND
THURS BEFORE THE LOW FINALLY WEAKENS AND MOVES INLAND TAKING THE
RAIN, SNOW, AND WIND WITH IT.

 AS FOR WINDS THE SOUTHERN PANHANDLE IS WINDY THIS MORNING WITH
GUSTS OF 40 TO 45 MPH AT HYDABURG AND ANNETTE. GALE FORCE WINDS
ARE ALSO OCCURRING IN THE SE GULF, CLARENCE STRAIT AND CROSS
SOUND. THOSE WINDS ARE EXPECTED TO SLOWLY FALL BELOW STRONG WIND
CRITERIA FOR HYDABURG AND ANNETTE THIS AFTERNOON BUT MAY REMAIN
SOMEWHAT GUSTY INTO TONIGHT. MOST OTHER PLACES WILL BE SEEING
SMALL CRAFT WINDS INTO TONIGHT AS THE FRONTAL BANDS CONTINUE TO
MOVE THROUGH. THE EXCEPTIONS WILL BE LYNN CANAL, SKAGWAY, AND THE
PASSES EAST OF YAKUTAT. THE COLD AIR AND STRONG PRESSURE GRADIENT
FROM THE NORTH WILL BE FILTERING INTO THE PANHANDLE STARTING TODAY
AND WILL INCREASE WINDS IN THESE AREA TO GALE FORCE TONIGHT WITH
POSSIBLE FREEZING SPRAY FOR LYNN CANAL AND GLACIER BAY AS AIR
TEMPS COOL DOWN.

 SHORT RANGE MODELS WERE IN DECENT AGREEMENT, HOWEVER THE DETAIL
WERE STILL IMPORTANT TODAY. MODEL SOUNDINGS WERE STILL AT ODDS ON
PRECIP TYPE ALONG ICE STRAIT TODAY WITH THE GFS WANTING HARDLY ANY
SNOW THROUGH THURS WHILE THE NAM JUST KEPT PILING IT ON HIGHER. AT
THE MOMENT IT LOOKS LIKE THE NAM IS WINNING OUT AS IT IS ALREADY
SNOWING IN MOST PLACES ALONG ICE STRAIT THOUGH THAT IS MORE DUE TO
SNOW MELT COOLING FROM THE HEAVIER PRECIP RATHER THEN A
SUBSTANTIAL INTRUSION OF COLD AIR FROM THE YUKON. DECIDED TO STICK
MORE TOWARD THE ECMWF AND GFS FOR UPDATES TODAY WHICH WERE MOSTLY
MINOR.

 &&

 .LONG TERM.../THUSDAY NIGHT THROUGH TUESDAY/ AS THE LOW PRESSURE
SYSTEM IN THE NORTHERN GULF CONTINUES TO WEAKEN THROUGH THURSDAY
NIGHT THERE WILL BE A BREAK IN PRECIPITATION AND WINDS OVER THE
PANHANDLE. THE STRONG NORTHERLY GRADIENT CAUSING GALE FORCE WINDS
OVER THE NORTHERN INNER CHANNELS REMAINS THROUGH FRIDAY AS THE
YUKON HIGH STAYS IN PLACE. SHIFT IN GRADIENT ORIENTATION WITH THE
NEXT SYSTEM WILL WEAKEN THESE WINDS AND THEN SHIFT TO THE SOUTH.
THE NEXT LOW PRESSURE SYSTEM EFFECTING THE REGION IS TRACKING
ACROSS THE N PACIFIC AND WILL REACH THE WESTERN AK GULF EARLY
FRIDAY. THE LOW WILL PROGRESS NORTHEASTWARD NEARING PRINCE WILLIAM
SOUND BY SATURDAY AFTERNOON. THE LOW WILL WEAKEN AND MOVE INTO THE
YUKON THROUGH MONDAY AS HIGH PRESSURE BEGINS TO BUILD OVER THE AK
GULF AND PANHANDLE NEXT WEEK.

 SUB TROPICAL MOISTURE WILL FEED INTO THE ASSOCIATED WEATHER FRONT
WHICH WILL MOVE ACROSS THE GULF FRIDAY AND THEN MOVE OVER THE
PANHANDLE SATURDAY INTO SUNDAY. MAY SEE 6 HOUR QPF VALUES NEARING
1 INCH WITH HEAVY RAIN OVER THE SOUTHERN PANHANDLE. UNLIKE THE
CURRENT LOW PRESSURE SYSTEM WITH A COLD ARCTIC FRONT FROM THE
INTERIOR THE WEEKEND SYSTEM IS MOVING A WARMER MID LEVEL AIR MASS
FURTHER TO THE NORTH WITH SURFACE TEMPERATURES RISING ABOVE
FREEZING. MOST REGIONS SHOULD SEE MORE RAIN THAN SNOW OUT OF THIS
SYSTEM. IF COLD AIR DOES LINGER FOR THE NORTH- CENTRAL REGIONS
COULD SEE HEAVY WET SNOW 12 HOUR ACCUMULATIONS IN THE 1 TO 4 INCH
RANGE. HIGHER AMOUNTS EXPECTED OVER THE NORTHERN PANHANDLE
HIGHWAYS WHICH COULD WARRANT ISSUING ANOTHER WINTER STORM WARNING.
AS THE LOW MOVES INTO THE NORTHERN GULF COLD AIR WILL PUSH DOWN
FROM THE INTERIOR WITH SURFACE TEMPS DROPPING BELOW FREEZING FOR
THE START OF NEXT WEEK. WITH WET SNOW AND RAIN POTENTIAL ICING
COULD BE AN ISSUE. PRECIP WILL BEGIN TO DIMINISH NEXT WEEK AS THE
HIGH PRESSURE RIDGE BEGINS TO BUILD OVER THE AREA.

 WINDS OVER THE GULF WILL INCREASE TO GALE FORCE WITH THE
ADVANCING FRONT OVER THE WEEKEND. WIND GUSTS OF 40 MPH ARE
EXPECTED ALONG THE PANHANDLE COAST. 850 MB LOW LEVEL JET WITH 50
TO 6O KT WINDS OVER THE SOUTHERN AK GULF WILL WEAKEN TO 40 KT AS
IT MOVES OVERLAND. STILL SOME DIFFERENCES IN THE POSITION OF THIS
LLJ.

 FAIR MODEL AGREEMENT WITH THE 00Z ECMWF AND GFS. THE NAM BECAME
AN OUTLIER EARLY, ESPECIALLY WITH TEMPERATURES DIFFERENCES IN MOS
GUIDANCE OF 20 DEGREES. USED A BLEND OF 00Z ECMWF/GFS WITH
INHERITED GRIDS THEN KEPT WITH WPC THROUGH DAY 8. WAVE MODELS WERE
DROPPING SEAS HEIGHTS OVER THE WEEKEND FROM PREVIOUS RUNS BUT DID
LIMIT THIS CHANGE. EXTENDED RANGE FORECAST CONFIDENCE IS AVERAGE
AS THERE IS STILL SOME DIFFERENCES WITH THE LOW PRESSURE CENTER
STRENGTH AND LOCATION BUT OVERALL SYNOPTIC SCALE FEATURES ARE IN
GOOD AGREEMENT.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL NOON AKST TODAY FOR AKZ027-028.
         WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON AKST
     THURSDAY FOR AKZ024.
         WINTER STORM WARNING UNTIL 4 PM AKST THURSDAY FOR AKZ019-020-025.
         WINTER STORM WARNING FROM NOON TODAY TO NOON AKST THURSDAY FOR
     AKZ022.
         WINTER STORM WARNING UNTIL NOON AKST THURSDAY FOR AKZ021.
         WINTER STORM WARNING UNTIL 9 PM AKST THIS EVENING FOR AKZ029.
         BLIZZARD WARNING UNTIL 4 PM AKST THURSDAY FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-013-021-022-031-034-036-041-043-051.
         SMALL CRAFT ADVISORY FOR PKZ011-032-033-035-042-052-053.

&&

$$

EAL/PRB