Winter Storm Warning 18, NWS Juneau, AK

223 
WWAK47 PAJK 150041
WSWAJK

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE JUNEAU AK
341 PM AKST WED DEC 14 2011

AKZ017-150145-
/X.EXP.PAJK.WS.W.0018.000000T0000Z-111215T0100Z/
CAPE FAIRWEATHER TO CAPE SUCKLING COASTAL AREA-
INCLUDING THE CITY OF...YAKUTAT
341 PM AKST WED DEC 14 2011

...WINTER STORM WARNING WILL EXPIRE AT 4 PM AKST THIS AFTERNOON...

THE WINTER STORM WARNING WILL EXPIRE AT 4 PM AKST THIS AFTERNOON.

HEAVY SNOW HAS MOVED EAST OUT OF THE AREA WITH IMPROVED VISIBILITY
THIS EVENING. THIS EVENING...SNOW SHOWERS WILL DIMINISH THROUGH
EARLY EVENING HOURS. ADDITIONAL SNOW ACCUMULATION UP TO 1 INCH
THROUGH EARLY EVENING HOURS.

THIS WILL BE THE FINAL STATEMENT OF THIS EVENT.

$$

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
521 AM AKST WED DEC 14 2011

.SHORT TERM...A WEAKENING WEATHER FRONT OVER THE CENTRAL GULF
WILL MOVE INTO THE EASTERN GULF THIS AFTERNOON AND DISSIPATE AS
IT MOVES ACROSS SOUTHEAST ALASKA TONIGHT. A SECOND FRONT WILL
MOVE INTO THE CENTRAL GULF BY THURSDAY MORNING.

 RADAR SHOWING SCATTERED SHOWERS MOVING ONSHORE NORTHERN HALF OF
SOUTHEAST ALASKA THIS MORNING. IN GENERAL QPF AMOUNTS WERE LESS
THAN 1 TENTH OF AN INCH OVERNIGHT WITH ONLY AN INCH OF NEW SNOW.
EXPECT PRECIP RATES TO REMAIN THE SAME THROUGH THE MORNING.
PRECIP BECOMES MORE WIDESPREAD AND ORGANIZED AS TROUGH APPROACHES
THIS AFTERNOON AND EVENING AND THINK INNER CHANNELS CLOUDS SEE
1 TO 2 MORE INCHES TONIGHT. COASTAL AREA HAVE MARGINAL TEMPS FOR
SNOW AND WILL KEEP THESE AREAS MIXED.

 OVERALL GRADIENTS ARE WEAK THIS MORNING AND WITH ONLY A WEAK
SURFACE TROUGH APPROACHING DO NOT EXPECT MUCH CHANGE IN WIND
SPEED. DO EXPECT TO SEE A SHIFT TO N THROUGH INNER CHANNELS THIS
AFTERNOON AHEAD OF SURFACE TROUGH BUT WILL GO BACK TO A SLY LATE
TONIGHT BEHIND SURFACE TROUGH. ELY WIND IN PKZ051 WILL INCREASE
THIS EVENING AND REACH MIN GALE BY LATE TONIGHT.

 NOT MUCH TEMPERATURE ADVECTION COMBINED WITH MOSTLY CLOUDY SKIES
DO NOT EXPECT BIG TEMPERATURE CHANGES THROUGH TONIGHT. TEMPS WILL
LIKELY CLIMB TO NEAR TO SLIGHTLY ABOVE FREEZING FOR INNER
CHANNELS THIS AFTERNOON BUT GO BACK INTO UPPER 20S BY THIS
EVENING. ALONG THE COAST WAA BEGINS LATER TONIGHT WITH TEMPS
RISING ABOVE FREEZING BY THURSDAY MORNING.

 GOOD MODEL AGREEMENT THROUGH THE SHORT TERM. EC SEEMED TO HAVE
BETTER INITIALIZATION OVER GULF WITH NAM ADDING IMPORTANT DETAILS
ACROSS SOUTHERN YUKON. USED A BLEND OF EC/NAM FOR PRES AND WINDS
THROUGH SHORT TERM.

 &&

 .LONG TERM...MODELS ARE IN FAIR AGREEMENT WITH OVERALL SYNOPTIC
PATTERN WITH MID LEVEL LONG WAVE RIDGE OVER BRITISH COLUMBIA AND
THE WESTERN US WITH A LONG WAVE TROUGH OVER THE BERING SEA AND N
PACIFIC. A SERIES OF SHORT WAVES FROM PARENT LOWS MOVING TOWARDS
THE BERING SEA WILL TRACK INTO THE AK GULF AND GENERALLY FOLLOW A
NORTHEASTERLY PATH TOWARD THE AK PANHANDLE. TIMING AND STRENGTH
OF THESE FEATURES IS NOT WELL ESTABLISHED WITH SOME FAIR MODEL
DIFFERENCES AND RUN TO RUN INCONSISTENCY. WHILE DETAILS ARE
SKETCHY ON THESE SYSTEMS EXPECTING MILD TEMPERATURE AND WET
WEATHER TO BE IN STORE.

 FOR THURSDAY A WEATHER FRONT WILL MOVE ACROSS THE AK PANHANDLE
WITH MIXED PRECIPITATION DEVELOPING THROUGH THE AFTERNOON. AS
HIGHEST QPF VALUES WILL BE LATER IN THE DAY ALONG WITH RISING
TEMPERATURES EXPECTING ANY SNOW ACCUMULATION TO BE 2 TO 3 INCHES
OR LESS DUE TO THE MIX OF RAIN. WILL ALSO SEE INCREASE IN WINDS
TO GALE FORCE OVER THE OUTSIDE WATERS AND COASTAL INNER CHANNELS.
THE MIXED PRECIP TREND WILL CONTINUE THROUGH THE LONG TERM AS
OVERNIGHT TEMPERATURES DROP INTO THE MID TO UPPER 20S WITH DAY
TIME HIGHS IN THE MID TO UPPER 30S.

 ECMWF AND GFS WERE IN FAIR AGREEMENT FOR THE START OF THE LONG
TERM, 12Z THURSDAY, TO 00Z SATURDAY WITH THE PASSING FRONT. THE
00Z RUNS WERE VERY SIMILAR TO INHERITED GRIDS SO CHANGES TO THIS
PART OF THE FORECAST WERE VERY MINOR. BY 00Z SATURDAY DIFFERENCES
IN POSITION OF A SHORT WAVE MOVING INTO THE AK GULF DEVELOPED
WITH THE ECMWF INDICATING A FASTER TRACK FURTHER TO THE NORTH.
THE 06Z GFS RUN FELL MORE IN LINE WITH THE ECMWF MOVING THE LOW
FURTHER NORTH COMPARED TO THE 00Z GFS. FOR THE REMAINDER OF THE
LONG TERM MODEL SPREAD INCREASED AND ALONG WITH RUN TO RUN
CONSISTENCY ISSUES, ESPECIALLY WITH THE GFS, DECIDED AN ENSEMBLE
APPROACH WAS THE BEST WAY TO GO SO KEPT WITH HPC GUID WITH SOME
ECMWF BLENDED IN. WHILE THIS DID WASHOUT SHORTWAVE DETAILS EXPECT
THAT EACH RUN OF THE ECMWF OR GFS WOULD PLACE THE LOW IN A NEW
LOCATION. NAM DID NOT INITIALIZED WELL SO WAS LEFT OUT OF THE
EQUATION WHILE EC RH FIELDS MATCHED UP WITH WAVER VAPOR IMAGERY
SO WAS USED MORE THAN THE GFS. FORECAST CONFIDENCE IS ABOUT
AVERAGE THEN DROPS RATHER RAPIDLY AS MODEL SPREAD INCREASES.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
         SMALL CRAFT ADVISORY FOR PKZ021-022-043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

MM/PRB