Gale Warning 400, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
537 AM AKST WED DEC 16 2009

.SHORT TERM...LOW PRESSURE WILL REMAIN NEAR PRINCE WILLIAM SOUND
THRU TONIGHT. ANOTHER LOW WILL TRACK N INTO THE NRN GULF TODAY AND
MERGE WITH THE OTHER LOW BY THIS EVENING. OCCLUDED FRONT WILL MOVE
ACROSS THE GULF TODAY THEN STALL JUST OFFSHORE SE ALASKA TONIGHT.
LOW PRESSURE WILL TRACK NE TO NEAR PRINCE RUPERT BY LATE THIS
AFTERNOON THEN DISSIPATE INLAND OVER BC TONIGHT.

MAIN CONCERN WILL BE PRECIP TYPE/AMTS. SHALLOW ARCTIC AIR REMAINS
OVER MOST OF THE INNER CHANNELS...BUT WILL BE ERODED AWAY FROM THE
S THRU TONIGHT. BY LATE TONIGHT...ONLY THE HYDER AREA AND FAR NRN
INNER CHANNELS SHOULD REMAIN BELOW FREEZING OVER THE MAIN
PANHANDLE AREA. CURRENTLY PRECIP IS FAIRLY LIGHT OVER THE NRN
PANHANDLE...BUT AN INCREASE IS EXPECTED AROUND THE HAINES AREA
TODAY AS OVERRUNNING OF ARCTIC AIRMASS INCREASES AS OCCLUDED FRONT
TO W MOVES CLOSER TO AREA. HAVE EXTENDED WINTER STORM WARNING FOR
HAINES ZONE THRU TONIGHT WITH 8 TO 15 INCHES OF SNOW EXPECTED BY
DAYBREAK THU. HAVE KEPT WINTER WEATHER ADVY FOR YAKUTAT AREA WITH
SNOW EXPECTED TO DEVELOP THIS MORNING. FLOW WILL BECOME MORE
ONSHORE THIS AFTERNOON AND THIS WILL LIKELY CHANGE THEM TO RAIN BY
LATE AFTERNOON. LOOKING FOR 3 TO 6 INCHES OF SNOW IN YAKUTAT BY THEN.
OVER THE HYDER AREA...DEFORMATION BAND ASSOCIATED WITH LOW MOVING
TOWARD THEM WILL BRING MODERATE PRECIP AMOUNTS...BUT FLUFF FACTOR
WILL MEAN SNOWFALL OF 4 TO 8 INCHES FOR THEM BY THIS EVENING.
ELSEWHERE...SNOW AMTS WILL BE GENERALLY AN INCH OR LESS BEFORE
AIRMASS WARMS UP TO CHANGE ANY PRECIP TO RAIN LATER THIS
AFTERNOON OR EVENING.

OTHERWISE...WILL KEEP WIND ADVY FOR HYDER ZONE GOING UNTIL 18Z
THIS MORNING. THIS LINES UP WELL WITH CANADIAN FORECAST FOR
STEWART AREA...AS WELL AS WHEN PRES GRADIENT DECREASES SOMEWHAT.
WILL SEE MORE WIND OVER THE GULF AHEAD OF OCCLUDED FRONT...WITH
MOST WIND LIKELY OVER NRN GULF. WENT WITH GALES FROM MARINE AREA
43 NWWD TO AREA 52 AHEAD OF THE FRONT...WITH SCA FURTHER S AND
OVER MOST OF THE INNER CHANNELS ESPECIALLY TONIGHT. HAVE MENTIONED
RISING TEMP TREND FOR MOST AREAS TONIGHT AS WELL.

&&

.LONG TERM...MODELS INTO THE WEEKEND TIME FRAME HAVE WORKED THERE
WAY INTO BETTER AGREEMENT...AS THE GFS SOLUTION AS SHIFTED TO
ALIGN WITH THE MORE WESTERN TRACK FOR THE LOW LATE THURSDAY INTO
FRIDAY MOVING NORTHWARD ALONG THE OUTER COAST AND MAKING LANDFALL
WHAT LOOKS LIKE BETWEEN YAKUTAT AND CROSS SOUND. THE ECMWF WAS
SHOWING THIS FOR SEVERAL RUNS PREVIOUSLY AND WAS IN THE GAME PLAN
ALREADY. FORECAST PACKAGE TODAY TO THE WEEKEND INCORPORATED GFS
DATA INTO THE CURRENT GRIDS.

WITH THE LOW MOVING NORTH LOOKING FOR SOME WINDY CONDITIONS
SETTING UP OVER COASTAL WATERS/ZONES SOUTH OF SITKA FOR LATE
THURSDAY INTO FRIDAY. WITH THE MORE WESTERN TRACK THIS IS ANOTHER
SLUG OF WARM MOIST AIR. ANY COLD AIR THAT MANAGES TO PERSIST OVER
THE NORTHERN PORTION OF THE PANHANDLE WILL LEAD TO ANOTHER ROUND
OF SNOW OF MODERATE ACCUMULATIONS.

A VERY COLD POOL OF AIR IS MOVING SOUTH TO SOUTHWESTERN PORTION OF
THE STATE BY THURSDAY MORNING AND THEN THIS WILL START TO SPREAD OUT
OVER THE WESTERN GULF (H850 TEMPERATURES -20 TO -26C) AND THEN
MOVE EASTWARD BEHIND THE UPPER LEVEL TROUGH AND WILL MOVE BACK TO
SOUTHEAST ALASKA WITH H850 TEMPERATURES OF -12 TO -18C. MAJORITY
OF THE PRECIPITATION SHOULD BE SHIFTING BACK TO SNOW SHOWERS
FRIDAY INTO SUNDAY TIME FRAME. A THOUGH IN THE UPPER LEVEL FLOW IS
EXPECTED TO START MOVING OVER A SMALL RIDGE OF HIGH PRESSURE OVER
THE EASTERN GULF BY SUNDAY MORNING.

IN THE LONG RANGE MODELS DEVELOPING A DEEP LOW AROUND 960 MB...BUT
IT IS HELD OVER THE SOUTH CENTRAL ALEUTIANS SATURDAY WITH A
SECONDARY DEVELOPMENT FEATURE GOING DEEPER INTO THE 940S BUT IT
ALSO CURLS NORTH INTO BRISTOL BAY THAT ASSOCIATED WEATHER FRONT
WILL TRY TO MOVE INTO THE EASTERN GULF EARLY NEXT WEEK. WHILE A
RIDGE OVER THE EASTERN PACIFIC NOSING NORTHWARD TO WESTERN CANADA
DOES ITS BEST TO KEEP THE SYSTEMS WEST OF THE FORECAST AREA.

CONFIDENCE IN THE LATE WEEK FORECAST IS FAIRLY GOOD WITH NEAR
AVERAGE FOR THE WEEKEND AND LATER.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 5 AM AKST THURSDAY FOR AKZ019.
         WINTER WEATHER ADVISORY UNTIL 6 PM AKST THIS EVENING FOR AKZ017-
     029.
         WIND ADVISORY UNTIL 9 AM AKST THIS MORNING FOR AKZ029.
MARINE...GALE WARNING FOR PKZ043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-022-031>036-041-042.

&&

RWT/BEZENEK