Gale Warning 429, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
412 PM AKST TUE DEC 11 2012

.SHORT TERM...LOW IN INTERIOR BC EXITING AND WEAKENING AS IT
DOES SO. THE CLOUDS ARE TRYING TO ERODE FROM THE NORTHERN AND
CENTRAL PANHANDLE WITH SOME STUBBORNNESS GOING ON. THE
STUBBORNNESS HAS BEEN A PERSISTENT LOCAL FOG AT THE JUNEAU
AIRPORT. SOME NORTHEAST FLOW OVER THE MOUNTAINS MAY HAVE INDUCED
A STRONGER INVERSION OVER THE MENDENHALL VALLEY AND SERVED TO
LOCK IN THE MOISTURE AND CONDENSATION ALREADY THERE. SINCE FOG
PERSISTED ALL AFTERNOON AND WE HAVE A WIDE SWATH OF CLEAR SKIES
OVER THE PANHANDLE TONIGHT ASSOCIATED WITH THE BUILDING RIDGE
OVER THE EASTERN GULF...HAVE ELECTED TO EXTEND THE DENSE FOG AT
LEAST THROUGH MIDNIGHT FOR JUNEAU. CONFIDENCE IS LOW. BUT FOR
GOOD MEASURE...ADDED AT LEAST PATCHY FOG THROUGH MOST ZONES WITH
EXCEPTION OF HAINES AND SKAGWAY. HAVE EXTENDED THIS INTO TOMORROW
MORNING AS WELL.

 BEHIND THE RIDGE WE HAVE THE NEXT FRONT BRINGING PRECIP IN THE
FORM OF SNOW AND RAIN TO YAKUTAT STARTING AS SNOW EARLY WEDNESDAY
MORNING THEN CHANGING TO RAIN. THE NORTHERN PANHANDLE RECEIVES
ITS DOSE OF PRECIP IN THE FORM OF CATEGORICAL POPS WED AFTERNOON.
THINK IT WILL BE MOSTLY RAIN IN DOWNTOWN JUNEAU AND NEAR THE
AIRPORT...BUT COULD BE ALL SNOW OUT THE ROAD AND DEEPER IN THE
VALLEYS. FARTHER SOUTH...AT LEAST CHANCES OF RAIN-SNOW WILL CREEP
INTO ZONE 26 AND SLIGHT CHANCES IN THE FAR SOUTHERN ZONES. THE
CLOUD SHIELD WITH THE FRONT SHOULD ENVELOPE THE ENTIRE PANHANDLE
BY LATE WED MORNING.

 MARINE WISE...SEAS WILL BUILD WITH THE RIDGE AND THUS EVEN AS
WINDS MAY NOT REACH SMALL CRAFT UNTIL WED AFTERNOON WITH FRONTAL
PASSAGE OVER THE SOUTHERN OUTSIDE WATERS...SMALL CRAFT WILL BE IN
ORDER FOR THE ENTIRE PERIOD. RIDGE WILL FLIP WINDS OVERNIGHT IN
LYNN CANAL...CHATHAM STRAIT...AND STEPHENS PASSAGE BY WED. SMALL
CRAFT WINDS DO NOT APPEAR IN THE INSIDE UNTIL LATE WED AFTERNOON
FOR MARINES 33-36. ALTHOUGH LATE WORD HAS WINDS IN STEPHENS
PASSAGE GETTING UP WITH SOME GAP FLOWS...SO HAVE SMALL CRAFT FOR
THEM THROUGH THE EVENING.

 HAVE MODIFIED SNOW TOTALS FOR TOMORROW AFTERNOON FOR THE
NORTHERN PANHANDLE...DECREASING THEM A BIT FROM EARLIER
PACKAGES...THINK THE INTRODUCTION OF RAIN AND THE FACT PRECIP MAY
ARRIVE ONLY IN THE AFTERNOON...SHOULD HOLD DOWN SNOW AMOUNTS TO
BELOW ADVISORY LEVELS...1 TO 3 IN JUNEAU...1 TO 2 IN GUSTAVUS.

 DID TWEAK SOME TEMPERATURES TO LOWER THEM FOR CLEAR SKIES
TONIGHT. BUT WITH SOME FOG IN JUNEAU...MAY BE TOO COLD LOCALLY AT
THE AIRPORT.

 MODEL OF CHOICE WAS ECMWF...BUT DID INCORPORATE SOME NAM WITH
IT. ECMWF SEEMED TO BE HANDLING LOW POSITION AND TRACK BETTER AND
LIKED THE FACT IT SEEMED TO WEAKEN THE INVERTED TROUGH TO THE
NORTHWEST TONIGHT. CONFIDENCE IN DENSE FOG TERMINATION NOT SO
GOOD. COULD LAST MOST OF THE NIGHT...BUT ELECTED TO GRADUALLY MIX
THINGS OUT TO ONE MILE AFTER MIDNIGHT. STAY TUNED FOR AMENDMENTS.

&&

.LONG TERM...A FRONT AFFECTING THE PANHANDLE IN THE SHORT RANGE
WILL CONTINUE TO BE A FACTOR IN THE BEGINNING OF THE EXTENDED
RANGE FORECAST PERIOD. HAVE SNOW TOTALS OVER PORTIONS OF THE
PANHANDLE FOR WEDNESDAY NIGHT THAT, WHEN COMBINED WITH SNOW
EXPECTED ON WEDNESDAY AFTERNOON, WILL APPROACH ADVISORY LEVELS BUT
ARE NOT EXPECTED TO EXCEED 4 INCHES IN 12 HOURS. SIGNIFICANT
THICKNESS TROUGH AND ASSOCIATED WEAK SURFACE RIDGING ON THURSDAY,
FOLLOWED BY ANOTHER FRONT LATE THURSDAY NIGHT INTO FRIDAY.
CURRENTLY HAVE VERY GOOD MODEL AGREEMENT ON THIS SECOND FRONT
WHICH IS A BOOST TO FORECAST CONFIDENCE. PRECIP ON THIS SECOND
FRONT SHOULD START OUT AS ALL SNOW EXCEPT FOR THE FAR SOUTHERN
ZONES. SYSTEM WILL BE OCCLUDING AS IT APPROACHES THE OUTER COAST
BUT THE LOW ITSELF WILL NOT HAVE YET MIGRATED INTO COLD AIR AND
THE WARM SECTOR LOOKS LIKE IT WILL BE STRONG ENOUGH TO DRIVE THE
RAIN-SNOW LINE UP TO OR PAST THE ICY STRAIT CORRIDOR BY FRIDAY
AFTERNOON. AM EXPECTING THE SNOW LINE TO MIGRATE BACK SOUTH AGAIN
OVERNIGHT FRIDAY INTO SATURDAY BEFORE THE PRECIPITATION DRIES UP.

LONG RANGE MODELS INDICATING ANOTHER PUSH TO THE SOUTH BY THE
ARCTIC FRONT EARLY NEXT WEEK. CURRENTLY HAVE GOOD AGREEMENT
BETWEEN GFS AND ECMWF SO WILL BE WATCHING THIS CLOSELY THROUGH THE
WEEK AHEAD.

POP AND QPF FIELDS UPDATED THROUGH FRIDAY NIGHT. NO SIGNIFICANT
CHANGES TO TEMPS OR SNOW LEVELS. PRESSURE AND WIND UPDATED USING A
BLEND OF GFS AND ECMWF THROUGH THE MID RANGE, THEN ECMWF AND HPC
SATURDAY THROUGH THE END OF THE LONG RANGE FORECAST. FORECAST
CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...DENSE FOG ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ025.
MARINE...GALE WARNING FOR PKZ041.
         SMALL CRAFT ADVISORY FOR PKZ012-031-033>036-042-043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-052.

&&

JWA/FRITSCH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
1020 PM AKST TUE DEC 11 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1016 PM     DENSE FOG        JUNEAU                  58.30N 134.41W
12/11/2012                                      AK   ASOS

            1/4 MILE FOG STARTING 10 AM TUE AND LIFTING AROUND 7 PM
            AT THE JUNEAU AIRPORT.

&&

PRB