Small Craft Advisory 735, NWS Juneau, AK

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

.SHORT TERM...OVERALL THE PATTERN HAS NOT ALTER SIGNIFICANTLY.
SAME VERTICALLY STACKED LOW WITH HIGH PRESSURE OVER NORTHWEST
CANADA. ORIGINALLY THOUGHT TONIGHTS FORECAST  ISSUE WAS GOING TO
BE THE WINDS ACROSS THE NORTHERN INNER CHANNELS. STORM FORCE
SUSTAINED OVER MARINE WATERS IN THE PANHANDLE...AND STRONGER
GUSTS AS WELL. REISSUED THE WARNING FOR TAKU WINDS IN THE JUNEAU
AREA THROUGH THE AFTERNOON AND EVENING. INITIAL THINKING IS THAT
IT SHOULD TAPER OFF THROUGH THE EARLY EVENING.

 FOR SATURDAY THE ISSUE WAS TO BE WINDS IN THE NORTH WITH SNOW
SPREADING INTO THE SOUTH CENTRAL PANHANDLE. SNOW AMOUNTS WAS TO
BE THE CONCERN BUT THOUGHT TO REMAIN BELOW ADVISORY BUT WITH
FURTHER REVIEW WAS COLDER AIR BEING PULLED SOUTH UNDER THE
SOUTHERLY AIR ALOFT. WILL BE GOING WITH SLIGHT CHANCE OF SOME
FREEZING RAIN LATE.

 ADDITIONAL MARINE PRODUCT ISSUE IS THE FREEZING SPRAY AND HEAVY
FREEZING SPRAY AFFECTING NORTHERN INNER CHANNEL AREAS SOME OUTER
WATERS NEAR YAKUTAT WITH THE STRONGER OUTFLOW LOCATIONS.

 &&

 .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 AND TURNS MORE EAST-WEST.

 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