Small Craft Advisory 762, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
347 PM AKST WED DEC 12 2012

.SHORT TERM...VERY ACTIVE SHORT TERM FORECAST PERIOD. A LOW OVER
THE SOUTH COAST VICINITY CAPE SUCKLING AS OF THIS AFTERNOON WILL
TRACK TO THE NORTHEAST AND INTO WESTERN CANADA OVERNIGHT.
BAROCLINIC CLOUD SHIELD NOW COVERS THE ENTIRE PANHANDLE AND THE
FRONT LIES OVER THE COASTAL MARINE ZONES AS OF THIS AFTERNOON.
COLD AIR AT THE SURFACE COMBINED WITH A WARMER OVERRUNNING
AIRMASS HAS PRODUCED PERIODS OF FREEZING RAIN IN HAINES AND
YAKUTAT TODAY AS WELL AS 4 INCHES OF SNOW IN YAKUTAT. WARMER AIR
IS WORKING ITS WAY TO THE SURFACE IN YAKUTAT AND ONCE WINDS VEER
TO THE SOUTHEAST ANY REMAINING SNOW WILL CHANGE TO RAIN.

WINDS HAVE COME AROUND TO THE SOUTHEAST IN HAINES AND
TEMPERATURES THERE JUMPED FROM 23 TO 34 DEGREES IN ONE HOUR.
BELIEVE HAINES WILL SEE MOSTLY RAIN TONIGHT WHILE THE HAINES
HIGHWAY NEAR THE BORDER WILL RECEIVE 4 OR MORE INCHES OF SNOW
TONIGHT BEFORE WARMER AIR ARRIVES. HAVE ISSUED A WINTER WEATHER
ADVISORY FOR THE HAINES ZONE AS A RESULT BUT HAVE SPECIFIED SNOW
ALONG THE HIGHWAY AS THE REASON WHY. LESSER AMOUNTS IN SKAGWAY,
BUT WIND THERE IS AN ISSUE. SOUTHERLY PRESSURE GRADIENT SET UP AND
WINDS VERY ABRUPTLY INCREASED WITH GUSTS 45 TO 50 MPH. HAVE STRONG
WINDS HEADLINE FOR THE SKAGWAY ZONE THROUGH TOMORROW. HAVE A GALE
WARNING FOR NORTH AND SOUTH LYNN CANAL TONIGHT, DIMINISHING TO
SMALL CRAFT BY TOMORROW MORNING. TEMPS ARE WARM ENOUGH THAT
FREEZING SPRAY IS NOT A FACTOR.

SOUTH OF THE ICY STRAIT CORRIDOR WIND IS NOT A SIGNIFICANT
FACTOR, BUT COLD AIR NEAR THE SURFACE AND A WARM SECTOR THAT MOVES
OFF TO THE SOUTHEAST FOCUSES ATTENTION OF SNOW TOTALS TONIGHT AND
TOMORROW MORNING. HAVE 2 TO 4 INCHES IN THE FORECAST TONIGHT FOR
PETERSBURG AND WRANGELL WITH LESSER AMOUNTS ELSEWHERE AND STRAIGHT
RAIN ALONG THE OUTER COAST FROM SITKA SOUTH AND INCLUDING
KETCHIKAN.

FOR TOMORROW, RAIN CHANGES TO SHOWERS AND GENERALLY DIMINISHES
THROUGH THE DAY AS THE SNOW LINE MIGRATES NORTH OF THE ICY STRAIT
CORRIDOR AS A RESULT OF A VERY STRONG AND DEEP ONSHORE PUSH. SMALL
CRAFT WINDS OVER THE INNER CHANNELS ALSO DIMINISHING THROUGH THE
DAY.

USED NAM FOR PRESSURE AND WINDS. BLENDED GEM, ECMWF, AND NAM FOR
POP AND QPF. ADJUSTED TEMPS USING MOS AND GFS. FORECAST CONFIDENCE
IS AVERAGE.

.LONG TERM...A BRIEF BREAK IN THE UNSETTLED WEATHER PATTERN WILL
COME TO AN END ON THURSDAY NIGHT AS A STRENGTHENING LOW DRIFTS
INTO THE NORTHERN GULF. AN ASSOCIATED SURFACE FRONT WILL CROSS THE
PANHANDLE FRIDAY. AM EXPECTING GALE FORCE WINDS WITH THIS FRONT
ACROSS THE SOUTHEAST GULF AND MANY OF THE SOUTHERN INNER CHANNELS.
WINDS WILL ALSO BECOME GUSTY ON THE LAND AREAS NEAR CLARENCE
STRAIT AND DIXON ENTRANCE AS A 50 TO 60 KT 850 MB LOW LEVEL JET
MOVES OVERHEAD. GUSTS AT THE SURFACE COULD REACH UP TO 40 MPH IN
THESE LOCATIONS AND A STRONG WIND HEADLINE MAY BE NEEDED IN LATER
FORECASTS. STRONG SOUTHERLY WINDS WILL KEEP THE SOUTHERN TWO
THIRDS OF THE PANHANDLE AS MOSTLY RAIN WITH THIS SYSTEM. THE
NORTHERN INNER CHANNELS WILL SEE IT START AS ALL SNOW BEFORE
WARMER AIR MOVES IN AND RAIN BEGINS TO MIX IN FRIDAY. A FEW INCHES
OF SNOW ACCUMULATION IS EXPECTED IN THE JUNEAU-GUSTAVUS-HOONAH
CORRIDOR BEFORE THE TRANSITION TO RAIN BEGINS. THE EXCEPTION WILL BE
ACROSS THE FAR NORTH IN THE HAINES AND SKAGWAY AREAS WHERE ENOUGH
COLD AIR MAY BE IN PLACE TO KEEP PRECIPITATION AS MAINLY SNOW.

WHILE THE MODELS DO DIVERGE ON THE HANDLING OF MULTIPLE WAVES
MOVING FROM THE NORTHERN PACIFIC INTO THE SOUTHERN GULF LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...THERE ARE GROWING
INDICATIONS OF ANOTHER ARCTIC OUTBREAK DURING THIS TIME PERIOD.
WITH THIS SETUP THERE WOULD BE A RETURN TO NORTHERLY WINDS LATE
SATURDAY NIGHT INTO EARLY NEXT WEEK...USHERING COLD DRY AIR INTO
THE NORTHERN HALF OF THE PANHANDLE. HIGH TEMPERATURES WOULD
STRUGGLE TO MAKE IT TO THE FREEZING MARK WITH LOWS FALLING INTO
THE TEENS AND SINGLE DIGITS ALONG THE HIGHWAYS. THIS WOULD ALSO
SUPPRESS MUCH OF THE PRECIPITATION TO THE SOUTHERN PANHANDLE.

USED A BLEND OF THE NAM/EC FOR THEIR HANDLING OF THE GALE FORCE
LOW ENTERING THE GULF LATE THURSDAY NIGHT. TRANSITIONED TO A BLEND
OF THE EC AND HPC IN THE LONG RANGE. FORECASTER CONFIDENCE IS
ABOVE AVERAGE THROUGH THE FIRST HALF OF THE WEEKEND AND THEN BELOW
AVERAGE INTO NEXT WEEK AS MODEL SOLUTIONS DIVERGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 6 AM AKST THURSDAY FOR AKZ019.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ018.
         WINTER WEATHER ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR
     AKZ017.
MARINE...GALE WARNING FOR PKZ012-013-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011-021-022-031>036-041-042-053.

&&

FRITSCH/TPS