Small Craft Advisory 681, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
418 PM AKST WED NOV 14 2012

.SHORT TERM...SATELLITE IMAGERY SHOWING A WARM FRONT PASSING
OVER THE AK PANHANDLE THIS AFTERNOON AND EARLY EVENING WITH
980 MB LOW OVER THE BERING SEA TRACKING TO THE SOUTHEAST. A SHORT
WAVE EXTENDING FROM THE BERING SEA LOW ALONG THE FRONT HAS FORMED
NEAR PRINCE WILLIAM SOUND AND IS CURRENTLY ROTATING TO THE
NORTHEAST. THE BERING LOW WILL MOVE OVER THE ALEUTIANS THROUGH
THE NIGHT FORMING A 990 MB LOW JUST SOUTHWEST OF KODIAK ISLAND.
THIS AK GULF LOW WILL DEEPEN AS IT DRIFTS TO THE SOUTHEAST AND
WILL INCREASE WINDS ALONG THE COASTAL GULF WATERS TO NEAR GALE
FORCE BY THURSDAY AFTERNOON. WHILE THIS LOW DROPS SOUTHEASTWARD
AN ARCTIC HIGH WILL BUILD OVER THE AK INTERIOR DROPPING INTO THE
YUKON BY THURSDAY AFTERNOON. THE TIGHTENING PRESSURE GRADIENT
WILL SHIFT WINDS TO THE NORTH AND INCREASE THEM THROUGH THURSDAY
AFTERNOON FOR THE NORTHERN INNER CHANNEL.

 THE WARM FRONT HAS INCREASE TEMPERATURES ACROSS THE ENTIRE
PANHANDLE TO A NEARLY UNIFORM 38 TO 44 DEGREES. PRECIPITATION HAS
TRANSITIONED TO ALL RAIN AND WILL BECOME SHOWERY THROUGH THE
EVENING AS COLDER UPPER AIR MASS MOVES IN BEHIND THE FRONT.
TEMPERATURES WILL DROP THROUGH THE EVENING A FEW DEGREES BUT ONLY
EXPECTING TEMPS TO DROP ENOUGH FOR A MIX OF SNOW NEAR YAKUTAT
HAINES AND SKAGWAY. ANY ACCUMULATION SHOULD BE MINOR WITH HIGHEST
AMOUNTS AT HIGHER ELEVATIONS. SHOWERS WILL CONTINUE THROUGH THE
DAY THURSDAY AS PRECIP BANDS FROM THE NEW AK GULF LOW MOVE OVER
THE PANHANDLE. MAY SEE SOME BRIEF HEAVY SHOWERS WITH THE PASSING
BANDS AS THERE IS A FAIR AMOUNT OF LIFT FROM THE COLD AIR ALOFT
AND HIGHER OMEGA VALUES. GUSTY SOUTH TO SOUTHEAST WINDS WILL
DIMINISH THROUGH THE EARLY EVENING AS THE FRONT CONTINUES TO
TRACK TO THE EAST. HAVE SEEN A FEW GUSTS NEARING 40 MPH BUT THESE
ARE NOT EXPECTED TO LAST VERY LONG. WINDS WILL SHIFT FROM
SOUTHERLY TO NORTHERLY AS THE GULF LOW DROPS TO THE SOUTH AND THE
YUKON HIGH BUILDS IN.

 MODELS WERE IN GOOD AGREEMENT TODAY WITH BEST MATCH BETWEEN THE
NAM/ECMWF. HOWEVER NAM QUICKLY BECOMES AN OUTLIER WITH THE
POSITION OF THE GULF LOW WHILE GFS/ECMWF FALL MORE IN LINE. USED
THESE TRENDS FOR MODEL BLENDS WITH INHERITED GRIDS. FORECAST
CONFIDENCE IS ABOVE AVERAGE.

 &&

.LONG TERM...UPPER LEVEL LONG WAVE TROUGH SETS UP OVER THE GULF
AT THE BEGINNING OF THE EXTENDED RANGE FORECAST WITH AN UPPER RIDGE
FARTHER UPSTREAM OVER THE BERING SEA. THE RIDGE CUTS OFF INTO A
HIGH OVER THE CHUKCHI SEA DURING THE WEEKEND AS A VERY STRONG
UPPER TROUGH DIGS TO THE SOUTHWEST ACROSS THE INTERIOR AND THE
UPPER LOW OVER THE GULF DIGS SOUTHEAST OVER WATER TOWARDS
WASHINGTON STATE. THE CHUKCHI HIGH RE CONNECTS WITH RIDGING FROM
THE SOUTH BY NEXT MONDAY AS THE LOW OVER THE GULF RETROGRADES
SLIGHTLY TO THE WEST AND THEN GETS PICKED UP BY A SHORT WAVE AND
TRACKS TO THE SOUTH AND EAST THROUGH MID WEEK. AT THE SURFACE, A
BROAD AREA OF LOW PRESSURE WITH NUMEROUS SMALLER CIRCULATIONS
WILL REMAIN IN PLACE OVER THE GULF THROUGH MID WEEK WHILE A STRONG
SURFACE HIGH REMAINS OVER THE BEAUFORT SEA AND NORTHERN INTERIOR.

LOW PRESSURE IN THE GULF WILL CONTINUE TO ROTATE PRECIPITATION
INTO THE PANHANDLE FOR MUCH OF THE UPCOMING WEEK WITH HIGHEST POPS
OVER THE SOUTHERN HALF. THE ARCTIC FRONT WILL BEGIN TO SAG SOUTH
AND REACH THE COAST MOUNTAINS OF THE FAR NORTHERN INNER CHANNELS
BY FRIDAY MORNING. WILL ALSO SEE SOME WRAP AROUND LOW LEVEL COLD
AIR ADVECTION APPROACHING THE PANHANDLE FROM THE WEST LATE IN THE
WEEKEND AND EARLY NEXT WEEK. MOSTLY RAIN ALONG THE OUTER COAST,
BUT LOCATIONS ON THE INSIDE SHOULD SEE MORE SNOW THAN RAIN AS DAY
TIME HIGHS AND OVER NIGHT LOWS GET LOWER AND LOWER THROUGH THE WEEK.
AT THIS TIME, ACCUMULATIONS EXPECTED TO REMAIN WELL UNDER WINTER
WEATHER ADVISORY CRITERIA.

BIGGEST STORY INT HE EXTENDED RANGE WILL BE WINDS ON FRIDAY. AS
THE ARCTIC FRONT SAGS SOUTH, THE RESULTING PRESSURE GRADIENT
BETWEEN THE BEAUFORT HIGH AND LOW PRESSURE IN THE GULF WILL
INTENSIFY AND PRODUCE STRONG NORTHERLY/OFFSHORE WINDS BEGINNING
FRIDAY AND LASTING INTO THE NEXT WEEK. HAVE GALE FORCE WINDS OVER
MANY OF THE INNER CHANNELS DURING THIS TIME FRAME.

NO FEEL YET FOR THE POTENTIAL FOR FREEZING SPRAY DURING THIS
TIME FRAME, BUT WILL WATCH CLOSELY OVER THE NEXT FEW DAYS.

BLENDED ECMWF TO EXISTING GRIDS THROUGH SATURDAY, THEN HEAVILY
BIASED THE PRESSURE AND WIND FORECAST TOWARDS HPC. POP AND QPF
WEIGHTED TOWARDS ECMWF. ADJUSTED TEMPS AND SNOW LEVELS USING GFS.
FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ012-036-043.
         SMALL CRAFT ADVISORY FOR PKZ013-021-022-031>035-041-042-051-052.

&&

PRB/FRITSCH