Small Craft Advisory 795, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
400 PM AKST SAT DEC 3 2011

.SHORT TERM...SATELLITE IMAGERY SHOWING MID LEVEL HIGH PRESSURE
RIDGE OVER THE EASTERN AK GULF TRACKING EAST WITH A WEAK WARM
FRONT OVER THE AK PANHANDLE AT THE SURFACE. THE MOIST ONSHORE
FLOW HAS BROUGHT LIGHT RAIN, DRIZZLE AND AREAS OF FOG TO MOST OF
THE REGION. BEHIND THE FRONT SOUTHWESTERN AREAS DID SEE A FEW
CLEAR BREAKS IN THE MORNING BUT THESE HAVE DIMINISHED AS NEXT
BAND OF CLOUDS MOVES IN. A SECOND SHORT WAVE AND ASSOCIATED
SURFACE FRONT WILL MOVES ACROSS THE AK GULF AND ONSHORE THIS
EVENING WITH THE FRONT CROSSING THE PANHANDLE THROUGH SUNDAY
MORNING. FOR THE NORTHER REGIONS DRIZZLE WILL CHANGE OVER TO
CATEGORICAL RAIN BECOMING HEAVY TO THE NORTHWEST AS THERE IS
AMPLE MOISTURE FEED MOVING OVER THE HIGH PRESSURE RIDGE. THE
FRONT WEAKENS TO THE SOUTH SO NOT EXPECTING AS MUCH PRECIPITATION
OVER AREAS SOUTH OF FREDERICK SOUND. A BARRIER JET FORMS ALONG
THE NORTHERN GULF COAST SUNDAY WITH GALE FORCE WINDS DEVELOPING.
OVER THE NORTHERN INNER CHANNELS SMALL CRAFT WINDS WILL INCREASE
AS NORTH-SOUTH PRESSURE GRADIENT DEVELOPS WITH HIGH PRESSURE
RIDGE OVER THE SOUTHERN PANHANDLE AND LOW PRESSURE IN THE YUKON.
OTHERWISE WINDS HAVE BEEN GENERALLY LESS THAN 15 KTS OTHERWISE.
WILL SEE ONLY SLIGHT DROP IN TEMPERATURES WITH OVERNIGHT NIGHT
LOWS IN THE MID TO LOWER 30S. WARM AIR MASS WILL REMAIN OVER THE
AREAS SUNDAY WITH HIGHS IN THE UPPER 30S TO LOWER 40S.

 MODELS WERE AGAIN IN FAIR AGREEMENT FOR THE SHORT TERM. GFS WAS
LOOKING MORE OF AN OUTLIER WHEN COMPARING SURFACE PRESSURE BUT
GFS DID LOOK A BIT BETTER THAN THE NAM TO THE WEST WHEN COMPARING
RH TO WATER VAPOR SATELLITE. UPDATED GRIDS WITH A BLEND OF 12Z
NAM AND ECMWF WITH INHERITED GRIDS, OVERALL CHANGES WERE FAIRLY
MINOR. FORECAST CONFIDENCE IS ABOUT AVERAGE.

&&

.LONG TERM...MAJOR FEATURE IN THE EXTENDED RANGE FORECAST WILL BE
HEAVY PRECIPITATION SUNDAY AFTERNOON THROUGH MONDAY EVENING THAT
WORKS ITS WAY FROM NORTH TO SOUTH ACROSS THE PANHANDLE. THE
SIGNIFICANT COOL DOWN THAT FOLLOWS THE ASSOCIATED COLD FRONT
SHOULD HAPPEN ON THE TAIL END OF THE PRECIPITATION SO THIS SHOULD
BE PRIMARILY A RAIN EVENT. COLD POOL OF AIR WILL REMAIN OVER THE
GULF AND PANHANDLE UNTIL WEDNESDAY NIGHT WHEN THE NEXT FRONT MOVES
IN FROM THE WEST. HAVE MOST OF THE COLD AIR GETTING DISPLACED IN
ADVANCE OF THE WEDNESDAY NIGHT FRONT BUT ENOUGH MAY REMAIN IN
PLACE THAT THE NORTHERN INNER CHANNELS AND MISTY FJORDS MAY SEE
A FEW INCHES OF NEW SNOW THURSDAY NIGHT THROUGH FRIDAY AFTERNOON.

.CLIMATE...THE HEAVY PRECIPITATION HEADED OUR WAY HAS A TROPICAL
CONNECTION EXTENDING ALL THE WAY BACK TO THE WESTERN PACIFIC. THE
CURRENT MJO EVENT IS CENTERED OVER THE MARITIME CONTINENT AND HAS
INCREASED IN STRENGTH OVER THE PAST COUPLE WEEKS. THE JET IS
LOCATED FAR ENOUGH TO THE SOUTH TO BE ABLE TO PICK UP SOME OF THE
MOISTURE ASSOCIATED WITH THE MJO ENHANCED CONVECTION AND CARRY IT
NORTH. IT IS POSSIBLE THAT THE PRECIP WE WILL SEE THIS SUNDAY
NIGHT, AND AGAIN NEXT THURSDAY NIGHT WILL HAVE BEEN ENHANCED BY
THE MJO. THE PNA IS CURRENTLY POSITIVE AND THIS MAY BE A
CONTRIBUTING FACTOR TO OUR SOMEWHAT WARMER WEATHER THESE RECENT
DAYS, COUNTERACTING THE TYPICAL COLDER-THAN-NORMAL LA NINA SEASON
TEMPERATURE TREND. THE PNA IS, HOWEVER, FORECAST TO WEAKEN AND
BECOME SLIGHTLY OVER THE COURSE OF THE NEXT WEEK, SO TEMPS MAY
BEGIN TO TURN COLDER AFTER THE SECOND FRONT LATE NEXT WEEK.

USED A BLEND OF NAM, GFS, AND ECMWF EARLY ON FOR POP AND QPF.
GRADUALLY SHIFTED MORE TOWARDS AN EVEN BLEND OF GFS AND EC IN THE
MID RANGE. ENDED WITH A MIX OF EC AND HPC. FORECAST CONFIDENCE IS
AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
         SMALL CRAFT ADVISORY FOR PKZ011-012-043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

PRB/FRITSCH