Winter Storm Warning 5, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
324 PM AKST WED FEB 12 2014

.SHORT TERM...A SURFACE LOW HAS FORMED OVER THE NORTHERN GULF
UNDERNEATH A LARGE UPPER LEVEL TROUGH. AN UPPER LOW WILL DROP
SOUTH FROM THE NORTHERN INTERIOR AND AID IN THE DEVELOPMENT OF
THIS FEATURE AS A BRANCH OF THE JET STREAM WRAPS AROUND THE BASE
OF THE UPPER LOW. FRONTOGENESIS IS ALSO APPARENT IN SATELLITE
IMAGERY AS OF THIS AFTERNOON. FURTHER SOUTH IN THE GULF, A
DEVELOPING WAVE IS TRACKING TO THE NORTHEAST. THE WAVE IS
EXPECTED TO MERGE WITH THE DEVELOPING FRONT AND THEN SWING NORTH
TOWARDS THE PANHANDLE TONIGHT. WHILE NOT A TRUE TRAINING EVENT,
MUCH OF THE ASSOCIATED QPF WILL BE CONCENTRATED IN THE YAKUTAT
AREA. AS OF THIS AFTERNOON, IT LOOKS LIKE THE HEAVIEST SNOWFALL
WILL OCCUR TO THE WEST OF THE BAY, BUT ENOUGH WILL FALL IN
YAKUTAT TO SUPPORT A WINTER STORM WARNING FROM TONIGHT THROUGH
THURSDAY AFTERNOON. TRAJECTORY ON THIS FRONT WOULD NORMALLY
RESULT IN RAIN, BUT NEAR SURFACE AIR TEMPERATURES OVER THE GULF
AS WELL AS SOUTHEAST ALASKA WILL RESULT IN SNOW AT THE STAR
REGARDLESS OF WHERE THE PRECIP IS COMING FROM. SETTLED ON A SNOW
RATIO OF 13 TO 1 AND WORKED UP A 24 HOUR SNOW FORECAST OF 9 TO
13 INCHES FOR THE TOWN OF YAKUTAT. BY TOMORROW MORNING, THE FRONT
WILL BEGIN WORKING ITS WAY SOUTH ALONG THE COAST AND SPREAD SNOW
INLAND. HAVE WINTER WEATHER ADVISORIES IN PLACE FOR BOTH HAINES
AND SKAGWAY TOMORROW AS A RESULT. OPTED TO CANCEL THE WIND CHILL
ADVISORY THAT WAS OUT FOR THE KLONDIKE HIGHWAY AND INCORPORATE
THAT ELEMENT INTO THE WINTER WEATHER ADVISORY FOR ZONE 17. SNOW
IS EXPECTED TO SPREAD ALL THE WAY DOWN THE PANHANDLE THROUGHOUT
THURSDAY AFTERNOON. THERE IS A LITTLE LOW LEVEL WARM AIR
ADVECTION ASSOCIATED WITH THE WARM SECTOR AND THE VERY PRONOUNCED
THICKNESS RIDGE ASSOCIATED WITH THE FRONT, SO THERE IS A GOOD
CHANCE THAT THE SOUTHERN OUTER COAST WILL WARM UP ENOUGH TO
PRODUCE A RAIN-SNOW MIX BY TOMORROW AFTERNOON. OUTSIDE THE
ADVISORY AND WARNING AREAS, SNOW TOTALS THROUGH TOMORROW
AFTERNOON RANGE FROM 3 TO 4 INCHES IN THE JUNEAU AREA TO LESS
THAN 1 INCH FOR THE SOUTHERN OUTER COAST.

 HIGH PRESSURE OVER WESTERN CANADA HAS RELAXED SOMEWHAT, BUT AN
OFFSHORE GRADIENT STILL EXISTS AS A RESULT OF THE DEEPENING LOW
OVER THE NORTHERN GULF. HAVE ISSUED GALE WARNING FOR THE OUTSIDE
COASTAL MARINE ZONES DOWN TO CAPE DECISION IN ADVANCE OF THE
APPROACHING FRONT. ALSO HAVE A GALE WARNING OUT FOR GLACIER BAY
AND CROSS SOUND. SMALL CRAFT ADVISORIES FOR MOST OF THE REMAINING
INNER CHANNELS WITH GUSTS TO 50 KTS OUT OF INTERIOR PASSES AND
DISENCHANTMENT BAY.

 USED A BLEND OF GEM, NAM, AND ECMWF FOR PRESSURE AND WIND. POP
AND QPF FROM NAM. TEMPS ADJUSTED PER GFS. OVERALL FORECAST
CONFIDENCE IS AVERAGE.

 &&

 .LONG TERM...COLD AND SNOWY WEATHER EXPECTED TO CONTINUE THROUGH
THE EXTENDED PERIOD AS A LONG WAVE UPPER TROUGH OVER THE GULF AND
ALASKA DOES NOT MOVE THROUGH THE WEEKEND. AT THE SURFACE THIS
RESULTS IN A VERY PERSISTENT LOW IN THE NORTHERN GULF WITH
SEVERAL SHORT WAVES OR LOWS ROTATING AROUND IT AND INTO THE
PANHANDLE IN THE SW FLOW. USUALLY THIS TYPE OF PATTERN WOULD
BRING US A DECENT WARM UP ACROSS THE PANHANDLE, BUT THE POOL OF
COLD AIR IN THE GULF HAS PUSHED SO FAR SOUTH THAT ANY LOWS IN THE
NORTHERN PACIFIC AND SOUTHERN GULF ARE FORMING ENTIRELY IN THE
POOL OF COLD AIR. SO WHEN THESE LOWS EVENTUALLY MAKE LANDFALL ON
THE PANHANDLE THEY DON'T HAVE MUCH OF A WARM PUSH AHEAD OF THEM
TO WARM THINGS UP. CONSEQUENTLY TEMPERATURES WILL REMAIN COLD
ENOUGH FOR SNOW FOR MOST AREAS, ESPECIALLY FOR THE NORTHERN HALF
OF THE PANHANDLE.

 STORM NUMBER ONE FOR THE LONG RANGE SHOWS UP ON THU NIGHT AND
FRI. STILL A LITTLE DISAGREEMENT FROM THE MODELS ON WHERE IT WILL
GO BUT THE MAIN CONSENSUS IS THAT THIS ONE IS LOOKING LIKE MAINLY
A SOUTHERN PANHANDLE STORM AGAIN AS THE MAIN LOW HEADS FOR THE
DIXON ENTRANCE AREA. TEMPERATURES SHOULD BE COLD ENOUGH FOR SNOW
BUT SOME AREAS ALONG PRINCE OF WALES ISLAND AND OVER TOWARD THE
SOUTHERN HALF OF CLARENCE STRAIT MAY WARM UP ENOUGH FOR THE SNOW
TO MIX WITH RAIN REDUCING SNOW AMOUNTS. HIGHEST SNOW AMOUNTS MAY
BE ALONG NORTHERN PRINCE OF WALES INTO PETERSBURG AND WRANGELL
WHERE QPF AMOUNTS WILL BE HIGHEST BUT TEMPS WILL STILL BE LOW
ENOUGH THAT RAIN SHOULD NOT MIX IN VERY MUCH. EXPECTING UPWARDS
OF 2 TO 6 INCHES FROM THIS STORM.

 NEXT STORM IS FRI NIGHT INTO SAT AND THIS ONE LOOKS LIKE MOST OF
IT WILL REMAIN OFFSHORE BUT IT WILL BRING QUITE A BIT OF WIND DUE
TO A STRONG PRESSURE GRADIENT BETWEEN IT AND THE RIDGE OVER
BRITISH COLUMBIA. WINDS ASSOCIATED WITH THE FRONT IN THE GULF
HAVE THE POTENTIAL TO GET TO MIN STORM FORCE LATE FRI NIGHT INTO
SAT BEFORE THE FRONT STARTS TO SLOWLY WEAKEN AND DRIFT EAST. THIS
SLOW DRIFT WILL GRADUALLY SPREAD THE HIGHER WINDS INTO THE INNER
CHANNELS. SMALL CRAFT ADVISORIES, GALE WARNINGS, MAYBE EVEN
STRONG WIND HEADLINES MAY BE NEEDED SAT AS THE FRONT GETS CLOSER
TO THE COAST. ANOTHER DUMP OF SNOW IS ALSO EXPECTED FOR THE
YAKUTAT AREA WITH THIS STORM. THE REST OF THE PANHANDLE WILL NOT
SEE MUCH AS MOST OF THE HIGHER PRECIP REMAINS OFFSHORE.

 PAST THE WEEKEND, MODELS DIVERGE WITH WHERE THE NEXT STORMS WILL
BE. THE GENERAL CONSENSUS SEEMS TO BE THAT THE PERSISTENT
NORTHERN GULF LOW WILL BEGIN TO DRIFT TO THE SE EARLY NEXT WEEK
AS A WEAK UPPER RIDGE BUILDS INTO THE GULF. THIS RESULTS IN THE
PANHANDLE DRYING OUT A BIT EARLY NEXT WEEK.

 EXTENDED RANGE MODELS WERE IN SOMEWHAT GOOD AGREEMENT THROUGH
THE WEEKEND WITH SOME DIFFERENCES HERE AND THERE. THE ECMWF WAS A
LITTLE BIT OF AN OUTLIER FOR THE SOUTHERN PANHANDLE STORM ON THU
NIGHT AS IT TOOK THE LOW FARTHER NORTH THEN ANY OTHER MODEL BUT
GOT BACK ON TRACK AFTERWARDS. DECIDED ON MORE NAM/GFS FOR THU
NIGHT INTO FRI THEN GFS/EC INTO THE WEEKEND. USED WPC FOR THE
REST OF THE EXTENDED TO EVEN OUT THE DIFFERENCES THAT SHOW UP
EARLY NEXT WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FROM 5 AM TO 4 PM AKST THURSDAY FOR
     AKZ019.
         WINTER WEATHER ADVISORY UNTIL 4 PM AKST THURSDAY FOR AKZ018.
         WINTER STORM WARNING UNTIL 4 PM AKST THURSDAY FOR AKZ017.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-022-042-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-031-033>036-041.

&&

FRITSCH/EAL

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE JUNEAU AK
1240 PM AKST WED FEB 12 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0630 PM     HEAVY SNOW       HYDER                   55.91N 130.02W
02/11/2014  M10.9 INCH                          AK   CO-OP OBSERVER

            CLIMATE DAY SNOWFALL. WAS STILL SNOWING AT TIME OF
            OBSERVATION.

0700 PM     HEAVY SNOW       10 S WRANGELL           56.33N 132.40W
02/11/2014  M6.5 INCH                           AK   TRAINED SPOTTER

            6.5 INCHES FOR THE DAYS SNOWFALL

0700 AM     HEAVY SNOW       30 NNW KLAWOCK          55.95N 133.39W
02/12/2014  M3.2 INCH                           AK   TRAINED SPOTTER

            TOTAL SNOWFALL AT EDNA BAY ALONG NORTHERN PRINCE OF WALES
            ISLAND.

0800 AM     HEAVY SNOW       COFFMAN COVE            56.01N 132.83W
02/12/2014  M5.0 INCH                           AK   CO-OP OBSERVER

            STORM TOTAL SNOWFALL FOR THE EVENT.

0800 AM     HEAVY SNOW       CRAIG                   55.47N 133.13W
02/12/2014  M2.2 INCH                           AK   CO-OP OBSERVER

            STORM TOTAL SNOWFALL FOR THE EVENT.

0930 AM     HEAVY SNOW       13 N KETCHIKAN          55.53N 131.65W
02/12/2014  M7.0 INCH                           AK   CO-OP OBSERVER

            STORM TOTAL SNOW ACCUMULATION FOR THE EVENT.

&&

RCL