Gale Warning 19, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
333 PM AKST TUE DEC 31 2013

.SHORT TERM...AFTERNOON SATELLITE IMAGERY SHOWS A 968 MB LOW
SOUTHWEST OF KODIAK ISLAND MOVING TO THE NORTH. THE ASSOCIATED
WEATHER FRONT EXTENDS OUT INTO THE EAST CENTRAL GULF. THE SYSTEM
HAS A TROPICAL MOISTURE CONNECTION EVIDENT BY THE LARGE SWATCH OF
MOISTURE ORIGINATING AROUND 30N. THE FRONT WILL BE THE MAIN
WEATHER MAKER THROUGH THE SHORT TERM FORECAST PERIOD AS IT MOVES
ACROSS THE PANHANDLE THROUGH WEDNESDAY AFTERNOON.

 WINDS WILL BE ON THE INCREASE ACROSS THE GULF REACHING GALE FORCE
THIS EVENING OUT OF THE SOUTHEAST. 40-50 KT 850 MB LOW LEVEL JET
MOVES OVER THE PANHANDLE LATE THIS EVENING AND OVERNIGHT WHICH IS
EXPECTED TO RESULT IN GUSTS TO 40 MPH FOR THE OUTER COASTAL
LOCATIONS AND IN THE VICINITY OF CLARENCE STRAIT BEFORE
DIMINISHING ON WEDNESDAY MORNING. EASTERLY GALE FORCE WINDS ARE
EXPECTED IN SUMNER AND CROSS SOUND TONIGHT AS THE FRONT PUSHES
INLAND AND THE E-W GRADIENT INCREASES. BEHIND THE FRONT WINDS WILL
SHIFT WESTERLY OVER THE GULF AND EXPECT 35 KTS OF WESTERLY WIND TO
DEVELOP IN CROSS SOUND AS THIS HAPPENS. SOUTHERLY WINDS WILL
INCREASE BEHIND THE FRONT IN THE INNER CHANNELS AS PRESSURE RISES
RESULT IN INCREASING SOUTHERLY GRADIENT.

 WINTER STORM WARNINGS OVER SKAGWAY AND HAINES REMAIN IN EFFECT
FROM MIDNIGHT TONIGHT THROUGH 6 PM WEDNESDAY. WINTER WEATHER
ADVISORY REMAINS IN EFFECT FOR JUNEAU FROM 6 PM THIS EVENING UNTIL
6 AM WEDNESDAY. EXPECTING BETWEEN 8 TO 18 INCHES OF SNOW IN THE
WARNING AREAS WITH HIGHEST AMOUNTS IN THE HAINES AREA. AS HAS BEEN
THE CASE FOR THE PAST WEEK PRECIPITATION TYPE IN THE JUNEAU AREA
REMAINS TRICKY BUT THINK PORTIONS OF THE VALLEY AND OUT THE ROAD
WILL PICK UP ADVISORY LEVEL AMOUNTS OF WET SNOWFALL IN THE 2 TO 6
INCH RANGE BEFORE WARMER AIR MOVES IN WEDNESDAY MORNING AND
CHANGES PRECIPITATION TO RAIN. MUCH OF THE REMAINDER OF THE
PANHANDLE CAN EXPECT RAIN TO BE HEAVY AT TIMES AS TROPICAL
MOISTURE STREAMS OVER THE AREA. BEHIND THE FRONT, STEADY RAIN WILL
TRANSITION TO SHOWERS ALONG THE OUTER COAST ON WEDNESDAY
AFTERNOON.

 USED A BLEND OF THE 00Z ECMWF AND 12Z GEM FOR UPDATES TO THE
SHORT RANGE FORECAST. FORECASTER CONFIDENCE REMAINS SLIGHTLY ABOVE
AVERAGE WITH STILL A BIT OF UNCERTAINTY ON THE PRECIPITATION TYPE
IN THE ICY STRAIT CORRIDOR TONIGHT.

 &&

 .LONG TERM...THE WEDNESDAY WEATHER FRONT WILL EXIT THE REGION TO
THE EAST THROUGH EARLY EVENING AS HIGH PRESSURE RIDGE OVER THE
EASTERN GULF MOVES OVER THE PANHANDLE. THE ORIGINAL PARENT LOW
WILL HAVE WEAKENED AND MOVED OVER THE AK PENINSULA WITH ANOTHER
SHORT WAVE TRACKING ACROSS THE AK GULF. THIS WAVE WILL REACH THE
NORTHWEST PANHANDLE WEDNESDAY NIGHT MOVING SOUTHEASTWARD OVER THE
REST OF THE REGION THROUGH THURSDAY EVENING. EXPECT SOME SHOWERS
FROM THIS SYSTEM WITH RAIN- SNOW LINE DROPPING TOWARDS SUMNER
STRAIT AS COLDER AIR MOVES IN BEHIND THE ORIGINAL FRONT. HEAVIEST
AMOUNTS WILL BE OVER THE YAKUTAT AREA WITH 2 TO 4 INCHES.
ELSEWHERE WITH WAVE SHEARING APART AND LOWER QPF VALUES SHOULD NOT
SEE SIGNIFICANT SNOW ACCUMULATIONS. HOWEVER WITH THE CONVECTIVE
NATURE OF THE SYSTEM SHOULD SEE HIGHLY VARIABLE SNOW AMOUNTS.

 FOR THE END OF THE WEEK MODELS ARE IN GOOD AGREEMENT ABOUT HIGH
PRESSURE BUILDING OVER THE AK GULF BUT THERE IS A SPLIT ON HOW FAR
NORTH THIS RIDGE WILL BUILD AND IF ANOTHER SHORT WAVE TRACING OVER
THE RIDGE WILL REACH OUR AREA. TO THE WEST OF THE RIDGE A LOW WILL
MOVING UP FROM THE PACIFIC NEARING THE ALEUTIANS EARLY SATURDAY. A
LOW DEVELOPING ALONG THE FRONT ASSOCIATED WITH THE MAIN LOW IS A
QUESTION FOR THE END OF THE WEEKEND. THE ECMWF HAS BEEN MORE
PROGRESSIVE WITH THE DEVELOPMENT OF THIS FEATURE AND HAS A MUCH
WARMER AND WETTER SOLUTION THAN THE GFS. THE DEVELOPMENT OF THIS
GULF LOW WILL ALSO INCREASE WINDS TO GALE FORCE ALONG THE COASTAL
WATERS WITH SMALL CRAFT WINDS OVER THE INSIDE CHANNELS.

 MODELS WERE IN FAIR AGREEMENT THROUGH FRIDAY BEFORE THE ISSUE OF
THE DEVELOPING HIGH OVER THE AK GULF. THOUGH OUT THE WEEKEND GFS
HAS REMAINED THE COLDER OF THE SOLUTIONS BUT WAS ALSO SHOWING MORE
RUN TO RUN INCONSISTENCY. ECMWF HOWEVER STARTED TO SHOW SHIFTS
WITH THE TIMING AND STRENGTH OF THE LOW DEVELOPING ON SUNDAY. SO
NO MODEL HAS BEEN THAT CONSISTENT. USED A BLEND OF 12Z ECMWF/NAM
THROUGH DAY 4 THEN TRANSITIONED TO WPC. NEW WPC USED MORE
OPERATIONAL 00Z ECMWF THAN ENSEMBLES AND SHOWED MORE CHANGES FROM
PREVIOUS FORECAST AND MODELS. DECIDED TO LIMIT THE CHANGES WITH
JUST A 50/50 BLEND OF 12Z WPC SEEING IF NEW MODELS RUNS FALL MORE
IN LINE. FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH WEDNESDAY MORNING
     FOR AKZ027-028.
         WINTER WEATHER ADVISORY UNTIL 6 AM AKST WEDNESDAY FOR AKZ025.
         STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH LATE TONIGHT FOR
     AKZ022-023.
         WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM AKST
     WEDNESDAY FOR AKZ018-019.
MARINE...GALE WARNING FOR PKZ022-035-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-031>034.

&&

TPS/PRB