Small Craft Advisory 19, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
607 AM AKST WED JAN 5 2011

.SHORT TERM...TRICKY FORECAST THROUGH TONIGHT. LOW PRESSURE
CURRENTLY DEVELOPING W OF THE CHARLOTTES WILL HEAD NWD BUT MODELS
DISAGREE GREATLY HOW FAR W THE LOW WILL TRACK. BASED ON
SAT/OBS...THINK THE LOW WILL BE HEADING TOWARD THE CAPE DECISION
AREA BY MIDDAY TODAY...THEN TURN MORE NNE THRU THE CENTRAL AREA
THIS AFTERNOON AND EVENING. THIS FURTHER EAST THAN PREVIOUS
FORECAST HAD IT. THE MODELS CLOSEST TO THIS TRACK WERE THE 00Z
GEM/06Z GFS/06Z NAM...WITH 00Z UKMET AND EC KEEPING LOW FURTHER
W. BUT THE EC AND UKMET HAVE TRENDED SLIGHTLY EWD WITH THE 00Z
RUN WHILE OTHERS HAVE TRENDED WWD...CONVERGING ON A TRACK TO NEAR
CAPE DECISION. THIS LOW TRACK WAS BASIS FOR THE FORECAST THROUGH
TONIGHT.

 WITH ABOVE IN MIND...MAIN CONCERNS WERE WINDS MAINLY ON S AND E
SIDE OF THE LOW...AND PTYPE ON W SIDE OF LOW TRACK ESPECIALLY
INLAND AREAS. ITS LOOKING LIKE A PERIOD OF ADVY LEVEL WINDS WILL
BE AFFECTING THE SRN AREA TODAY...WITH PEAK THREAT BETWEEN 17-21Z
AS LOW IS MOVING BY THEM TO THEIR W. HAVE ISSUED WIND ADVYS FOR
THE SRN THREE ZONES FOR THE 15Z-01Z PERIOD...AS THERE COULD ALSO
BE A BIT OF STRONGER WIND IN A WRAP AROUND BAND DURING THE EARLY
AFTERNOON. HAVE GALES FOR CLARENCE STRAIT FOR MOST OF THE DAY
TOO. WINDS MOST OTHER AREAS WILL SHIFT FROM SLY TO NLY EARLY
TODAY BUT SHOULD REMAIN BELOW SCA OVER THE NRN HALF OF THE
AREA...WHILE REMAINING SRN AREAS GET SCA LEVEL E-SE WINDS TODAY.
AS LOW PULLS NWD AND INLAND WSW SCA LEVEL WINDS ARE LIKELY OVER
THE SE GULF THIS AFTERNOON AND TONIGHT.

 AS FOR PTYPE...PAJN-PAGS-PAOH AREAS HAVE BEST CHANCE FOR
SNOW...AND IT IS PROBABLE THAT SNOW WILL OCCUR WITH WINDS
BECOMING LIGHT...AND PRECIP RATES AROUND .05 IN/HR LIKELY
ESPECIALLY PAJN/PAOH AREAS TONIGHT. WILL GO WITH RAIN AND SNOW
FOR THESE AREAS AS CONDITIONS WILL BE HIGHLY VARIABLE ACROSS THE
ZONE. SNOW ACCUMS LOOK TO BE AROUND 3 INCHES AROUND PAJN WITH AN
INCH OR 2 IN THE PAGS AND PAOH AREAS. THERE IS A RISK OF HEAVIER
AMTS AROUND PAJN DUE TO FLOW LIKELY BECOMING SWLY BY LATE EVENING
AND UPSLOPE ENHANCING PRECIP RATES...BUT THIS WILL DEPEND ON
EXACT STRUCTURE/TRACK LOW TAKES WHICH REMAINS TRICKY AT THIS
POINT.

 OTHERWISE...SHOULD SEE PRECIP OVER THE FAR NRN AREA DIMINISH
THIS MORNING AS FLOW BECOMES OFFSHORE...WITH THE PAYA AREA SEEING
THEIR PRECIP DIMINISH THIS AFTERNOON AS OFFSHORE SHIFT OCCURS
THEN. ALL IN ALL...NOT VERY HIGH CONFIDENCE IN MANY ASPECTS OF
THE FORECAST...BUT SOMEWHAT CONFIDENT THAT ADVY LEVEL WINDS WILL
OCCUR  OVER THE SRN AREA.

&&

.LONG TERM...UPPER LEVEL TROUGH OVER THE EASTERN GULF MOVES ACROSS
SOUTHEAST ALASKA THURSDAY AND THEN DIGS SE FRIDAY. AT THE SURFACE
A LOW DIGS SE THURSDAY AS ARCTIC FRONT PUSHES SOUTH THROUGH
PANHANDLE. A DEVELOPING 500 MB HIGH BUILDS FROM THE WESTERN GULF
AND BECOMES AN IMPRESSIVE CLOSED OFF HIGH OVER NORTHWEST ALASKA BY
MONDAY AND NEARING 580 DM. THIS WILL KEEP THE EASTERN HALF OF THE
STATE DRY AND SUPPORT THE DEVELOPMENT OF AN INTENSE ARCTIC AIRMASS
AND 1055+ MB SURFACE HIGH OVER WETERN CANADA THROUGH THE MIDDLE OF
NEXT WEEK. A RETROGRADING LOW FROM WESTERN CANADA TO NE GULF COULD
BE INTERESTING MID TO LATE NEXT WEEK BUT SINCE IT WAS A NEW
SOLUTION OPTED STAY THE DRY COURSE FOR NOW.

EXPECT PRECIP ACROSS SOUTHERN TWO THIRDS OF PANHANDLE THURSDAY-
THURSDAY NIGHT WITH JUST CHANCE TO THE NORTH. WILL SEE DRYING FROM
THE NORTH FRIDAY WITH PRECIP ENDING ACROSS SOUTHEAST ALASKA BY
SATURDAY MORNING. WITH COLD AIR FILITERING IN WILL SEE PRECIP
CHANGE TO SNOW CENTRAL THU AND SOUTHERN FRI. WITH DRIER AIR
SPREADING SOUTH AS WELL LIMITED SNOW AMOUNTS TO THE 1 TO 3 INCH
RANGE.

SIGNIFICANTLY COLDER AIR MASS FOLLOWS BY LATE WEEKEND WITH
NORTHEAST GRADIENTS INCREASING. EXPECT SOLID GALES IN NORTHERN
INNER CHANNELS BY SAT AND CONTINUING THROUGH THE WEEK. FREEZING
SPRAY WILL ALSO BE A FACTOR. COASTAL AREA WILL SEE DECREASING
SWELL THU.

USED THE EC FOR GRIDS ALTHOUGH THE 06Z GFS AND NAM LOOKED REALLY
GOOD. HAD TO UP EC WINDS BY AT LEAST 5 KT. IN EARLY PERIODS HAD
TO INCREASE POPS BUT CUT BACK HPC POPS FOR LATER PERIODS. PLAYED
AROUND WITH DAYS 2-3 TEMPS AND LEFT REMAINDER UNCHANGED.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR AKZ027>029.
MARINE...GALE WARNING FOR PKZ036.
         SMALL CRAFT ADVISORY FOR PKZ012-033-041-042.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-043-051-052.

&&

RWT/MM