Small Craft Advisory 737, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
411 PM AKST SAT DEC 1 2012

.SHORT TERM...GUSTY OUTFLOW WINDS PERSISTING ACROSS THE NORTHERN
PANHANDLE FROM HIGH PRESSURE IN CANADA A WEAKENING LOW NEAR HAIDA
GWAII THAT WILL BE MOVING NORTHWARD TO BE WEST OF PRINCE OF WALES
ISLAND BY SUNDAY AFTERNOON.

MOISTURE SPREADING NORTH ABOUT THE LOW INTO THE SOUTHERN AND
CENTRAL PANHANDLE IS PROMPTING THE PRECIPITATION ACROSS THE
PANHANDLE. RAIN SNOW LINE SEEMS TO BE STRUNG OUT ACROSS PRINCE OF
WALES ISLAND...SOUTHERN INNER CHANNELS...AND MISTY FJORDS. LIGHT
SNOW HAS SPREAD NORTH TO THE JUNEAU AREA BUT THE FLAKES ARE ON THE
DRY SIDE.

THE LOW IS PROVIDING THE MOISTURE AND A SHORT APPROACHING FROM
THE WEST NORTHWEST AND THIS IS EXPECTED TO ENHANCE THE LIFT AND
SNOWFALL ACROSS THE CENTRAL AND NORTHERN PANHANDLE TONIGHT THROUGH
SUNDAY WITH THE NORTHERN SECTION LATER THROUGH THE EVENING AND
SUNDAY. WAS SLIGHTLY CONCERNED ABOUT LACK OF MOISTURE BASED BY
SATELLITE IMAGERY ESTIMATES AND QPF NUMBERS FROM SOLUTIONS OVERALL
WITH ONLY ONE OR TWO MODELS WITH BETTER QPF IN IT. WITH THIS IN
MIND HAVE SOME MINOR CONCERNS REGARDING THE AMOUNTS OF SNOWFALL.
WILL BE HAVING NEXT SHIFT CHECK MY CONCERN AND MAKE DETERMINATION
ABOUT THE WATCH FOR HEAVY SNOW ACROSS THE HAINES THAT IS TO START
SUNDAY.

FORECAST CONFIDENCE IS IN THE AVERAGE RANGE THROUGH SUNDAY.

&&

.LONG TERM...NOT MUCH VARIATION IN THE EXTENDED PERIODS TODAY. A
MEANDERING LOW REMAINS IN THE GULF THROUGH MUCH OF THE PERIOD
WITH AN AREA OF COLD HIGH PRESSURE REMAINING ENTRENCHED IN THE
YUKON. THE MOST VARIATION WILL BE FROM THE VARIOUS SHORT WAVES
THAT ARE ROUNDING THE BASE OF THE GULF LOW THROUGH NEXT WEEK.

THE FIRST OF THE WAVES WILL BE STARTING TO WEAKENING ALONG THE
SOUTHERN OUTER COAST SUN NIGHT AFTER BRINGING ALL THE SNOW TO THE
NORTHERN AND CENTRAL PANHANDLE ON SUN. SNOW WILL BE CONTINUING
THROUGH SUN NIGHT THOUGH AT A REDUCED RATE AS SOUTHERLY
OVERRUNNING FLOW WEAKENS WITH THE LOW. BY MON SOME LIGHT SNOW MAY
STILL BE AROUND DUE TO SOME WEAK UPPER LEVEL VORTICITY MAXES
MOVING THROUGH BUT ADDITIONAL ACCUMULATIONS WILL BE LIGHT. THE
NEXT GOOD CHANCE OF SNOW MAINLY FOR THE SOUTHERN AND CENTRAL
PANHANDLE COMES MID WEEK WITH THE ARRIVAL OF THE NEXT WAVE. MODELS
STILL DON'T HAVE THE GREATEST HANDLE ON IT AS THEY ARE BACK TO A
STRONGER LOW BEING PRODUCED OUT OF IT AND THEY ARE TAKING IT MUCH
FARTHER EAST. THE LOW IS NOW COMING UP HECATE STRAIT RATHER THEN
THE WEST SIDE OF HAIDA GWAII. THINGS GET EVEN MORE COMPLICATED
ONCE IT REACHES THE SOUTHERN PANHANDLE. NAM IS SPLITTING THE LOW
IN TWO WITH PART OF IT GOING INTO CANADA AND THE REST HEADING UP
THE OUTER COAST. GFS AND ECMWF ON THE OTHER HAND KEEP IT MOSTLY
TOGETHER AND BRING IT UP THE OUTER COAST. IN EITHER CASE THE COLD
AIR IN THE INNER CHANNELS IS STILL THERE SO SNOW IT A GOOD
POSSIBILITY FOR THE CENTRAL INNER CHANNELS AGAIN ON TUES NIGHT
INTO WED.

FARTHER NORTH THE HIGH IN THE YUKON WILL HANG AROUND THROUGH THE
PERIOD THROUGH NOT AS STRONG AS IT HAS BEEN. THE REINFORCING SHOTS
OF COLD AIR ARE BEING DIRECTED TOWARD WESTERN ALASKA SO IT IS ONLY
THEIR BECAUSE OF THE TRAPPED COLD AIR ON THE CANADIAN SIDE OF THE
COAST MOUNTAINS. THERE ARE NO SYSTEMS COMING THROUGH THAT WILL
PUSH THAT COLD AIR OUT OF THERE EITHER SO IT WILL REMAIN THERE FOR
THE NEXT WEEK AT LEAST. AS A RESULT COLD OUTFLOW WINDS WILL STILL
BE FLOWING OUT OF THE VARIOUS INTERIOR PASSES THROUGH MID WEEK.
GALES AND FREEZING SPRAY ESPECIALLY IN LYNN CANAL WILL BE THE RULE
FOR THE MOST PART. A REDUCTION IN THE WINDS IS LOOKING TO BE IN
THE WORKS FOR WED NIGHT AND BEYOND AS THE GULF LOW FINALLY WEAKENS
AWAY AND THE PRESSURE GRADIENT ACROSS THE NORTHERN PANHANDLE
SLACKENS.

LONG RANGE MODELS ARE IN DECENT AGREEMENT THROUGH THE WEEKEND BUT
AS DESCRIBED ABOVE DIVERGE A BIT BY TUES. THERE ARE ALSO
SIGNIFICANT DIFFERENCES THAT POP UP LATER IN THE WEEK PARTICULARLY
WITH SNOW LEVEL BETWEEN THE GFS AND ECMWF. DECIDED ON A BLEND OF
THE ECMWF AND NAM FOR THE MID RANGE AS THEY STILL HAVE A GOOD
REPRESENTATION OF THE PRESSURE GRADIENT ALONG THE COAST MOUNTAINS.
USED HPC/ECMWF FOR TUES ONWARD FOR A MORE MIDDLE OF THE ROAD
APPROACH TO THE EXTENDED GRIDS. FORECAST CONFIDENCE IS ABOUT
AVERAGE FOR TO MON THEN FALLS TO BELOW AVERAGE AFTER THAT.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 6 AM AKST SUNDAY FOR AKZ023-024-026.
         WINTER STORM WARNING UNTIL 4 PM AKST SUNDAY FOR AKZ021-025.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ017-019-029.
         WINTER STORM WATCH FROM SUNDAY MORNING THROUGH LATE SUNDAY NIGHT
     FOR AKZ019.
         STRONG WIND UNTIL 6 PM AKST THIS EVENING FOR AKZ018.
         WIND CHILL ADVISORY UNTIL 5 AM AKST SUNDAY FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ012-013.
         STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031-032-036-051.
         SMALL CRAFT ADVISORY FOR PKZ033>035-043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

BEZENEK/EAL