Gale Warning 37, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
316 PM AKST FRI JAN 9 2009

.SHORT TERM...SNOW IN THE NORTH AND RAIN IN THE SOUTH AND ALONG
THE CENTRAL AND SOUTHERN COAST CONTINUE THIS MORNING AS A 988 MB
LOW CENTERED 120 MILES SOUTH SOUTHWEST OF YAKUTAT WEAKENS AND
MOVES ONSHORE TODAY INTO TONIGHT. CURRENTLY HEAVY BANDS OF PRECIP
ARE MOVING ONSHORE AS EVIDENCED BY THE MODERATE RAIN FALLING AT
SITKA AND THE HEAVY SNOW WITH 1/4 MILE VISIBILITY OBSERVED AT
ELFIN COVE THIS MORNING WITH LIGHTER PRECIP RATES FARTHER INLAND.
RADAR SHOWS THAT THE BACK EDGE OF THE PRECIP IS APPROACHING THE
COAST. THE MORE STRATIFORM PRECIP SHOULD BE CHANGING OVER TO A
MORE CONVECTIVE NATURE AND BECOME MORE SCATTERED AS THE DAY WEARS
ON. WINDS ARE STILL BLOWING IN SKAGWAY AND WHITE PASS CREATING
BLIZZARD CONDITIONS ALONG THE KLONDIKE HIGHWAY DUE TO BLOWING
SNOW.

 UPPER LEVEL PATTERN IS FAIRLY FLAT OVER THE AREA WITH AN UPPER
LOW OVER WESTERN ALASKA AND A TROUGH OVER NORTHERN ALASKA AND THE
NORTHERN YUKON. PATTERN WILL GRADUALLY GIVE WAY TO A WEAK RIDGE
PATTERN OVER THE AREA BY SATURDAY.

 THE REMAINING MOISTURE AND SOME WEAK ISENTROPIC LIFTING OVER THE
AREA DOES NOT RULE OUT CONTINUING RAIN OR SNOW SHOWERS THROUGH
SATURDAY MORNING. BY SATURDAY AFTERNOON OUR NEXT SYSTEM WILL BE
APPROACHING THE PANHANDLE AND WILL BE STARTING TO AFFECT THE
SOUTHERN ZONES AS A SURFACE TROUGH COMES IN FROM THE SOUTHWEST
ACCOMPANIED BY SOME WEAK QVECTOR FORCING IN THE UPPER LEVELS.
SNOW FALL AMOUNTS...WHERE IT IS COLD ENOUGH FOR SNOW...ARE
EXPECTED TO BE LIGHT ACROSS THE AREA THROUGH SATURDAY AFTERNOON.
WINDS ACROSS THE AREA ARE EXPECTED TO LESSEN AS THE CANADIAN HIGH
WEAKENS THROUGH THE SHORT TERM PERIOD.

 MODELS WERE AGAIN IN FAIRLY GOOD AGREEMENT THROUGH THE FORECAST
PERIOD WITH ONLY SLIGHT VARIATION IN LOW POSITION IN THE GULF.
FORECAST WAS UPDATED WITH A BLEND OF THE CURRENT GRIDS AND A
GFS/NAM/GEM COMBINATION. A LITTLE LESS WEIGHT WAS PLACED ON THE
GEM THEN THE OTHER MODELS SO AS NOT TO OVERDO THE STRENGTH OF THE
CANADIAN HIGH IN THE FORECAST.

&&

.LONG TERM...
WSW FLOW ALF GRADUALLY BACKS AROUND TO S BY WED NEXT WK. STORM
TRACK CONTINUES TO AIM AT SE AK BUT SATELLITE IMAGERY SHOWS
PRECIPITABLE WATER AMOUNTS UPSTREAM ARE GREATLY REDUCED NOW. MAIN
MOISTURE PLUME OVER WEEKEND WILL BE S OF PANHANDLE. A VORTEX NEAR
45N 170W TODAY WILL LIFT NE ALG THE BACK SIDE OF THE MOISTURE
FETCH AND DRAG IT NWD OVER THE PANHANDLE SUN-MON FOR RENEWED
PCPN.
SO BETWEEN NOW AND THEN THE ARCTIC FRONT WAFFLES OVER THE
SOUTHERN
ONE THIRD TO ONE HALF OF THE PANHANDLE. PCPN WILL BE MAINLY IN
FORM OF RAIN S OF CAPE SPENCER TO PAPG-PAWG AND TO MISTY FJORDS.
EVEN THOUGH PCPN SHOULD BE SNOW NORTH OF THIS FRONT IT WILL
LIKELY
BE ONLY SEVERAL INCHES AND HAVE HIGHER WATER CONTENT OVER TIME
AND
LOSE ITS CHAMPAGNE POWDER CHARACTERISTIC.

THE LOW CENTER APPROACHING THE GULF SUN-MON IS EXPECTED TO STAY W
OF THE JNU FORECAST AREA AND TRACK TWD PRINCE WM SOUND. THIS IS
MAINLY DUE TO BUILDING UPR RIDGE ALG W CONUS COAST NOSING NWD
MON-
WED INTO CENTRAL BC. BELIEVE THE PCPN SUN-MON WILL BEHAVE LIKE A
WARM FRONT AND LIFT N OVER THE FORECAST AREA. TEMPS ON S SIDE OF
THIS FEATURE ARE NOTABLY WARMER...EVEN ABOVE AVE. I EXPECT THIS
PASSAGE OF THIS SYSTEM WILL ALSO KILL THE ARCTIC FLOW INTO N LYNN
CANAL. SLY LOW LVL WINDS AND MILDER TEMPS SHOULD BE IN PLACE OVER
ENTIRE FCST AREA BY WED. VERY LATE NEXT WEEK THE STRONG WLY JET
ACROSS PAC AT 35N SPLITS WHEN IT ENCOUNTERS W CST RIDGE. THE
BRANCH
TURNING N MAY NUDGE CLOSE ENOUGH TO PANHANDLE WITH A RAIN MAKER.
BUT THAT IS WAY IN THE FUTURE. THE GOOD NEWS WITH THIS PATTERN
CHANGE IS THAT THE WARM FRONT LIFTS STEADILY INTO S CENTRAL AK SO
A PROLONGED WARM RAIN EVENT ON THE ABUNDANT SNOW PACK...OVER 40
INCHES ON GRND NEAR SEA LEVEL IN PARTS OF PANHANDLE... DOES NOT
SEEM LIKELY RIGHT NOW.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 6 PM AKST THIS AFTERNOON FOR
     AKZ019>022-024>026-029.
         BLIZZARD WARNING UNTIL 6 PM AKST THIS AFTERNOON FOR
AKZ018.
         WINTER WEATHER ADVISORY UNTIL 6 PM AKST THIS AFTERNOON
FOR
     AKZ017.
MARINE...GALE WARNING FOR PKZ012-051.
         SMALL CRAFT ADVISORY FOR
PKZ011-013-021-022-031>036-041>043-052.

&&

EAL/TA