Gale Warning 13, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1233 PM AKST WED JAN 28 2009

.SHORT TERM...COMPLEX FEATURES IN THE AK GULF PROVIDING A
COMPLEX FORECAST FOR SE AK. PARENT LOW OVER THE ALEUTIANS WITH
FRONTAL BANDS OVER THE AK GULF TRACKING PRECIPITATION ACROSS THE
ENTIRE PANHANDLE. EARLIER CYCLOGENESIS AT THE TRIPLE POINT HAS
NOT BEEN DEVELOPING AS MUCH AS WAS EARLIER ANTICIPATED. SNOW FROM
FREDERICKS SOUND NORTH, A MIX OF RAIN AND SNOW ALONG THE COASTAL
REGIONS AND SOUTH CENTRAL PANHANDLE AND ALL RAIN SUMNER STRAIT
SOUTH. COLDER AIR IS BEING MOVED OUT A BIT SLOWER THAN
ANTICIPATED KEEPING SOME OF THE NORTH CENTRAL REGION AS SNOW
LONGER THAN ANTICIPATED, BUT HAVE SEE SOME RAPIDLY INCREASING
TEMPERATURES. WINTER WEATHER ADVISORY FOR PAYA WAS TERMINATED
EARLY AS WINDS SHIFTED TO THE SOUTH TRANSITIONING FROM SNOW TO A
RAIN SNOW MIX. SKAGWAY WIND GUSTS INCREASED TO ADVISORY LEVELS
WITH THE RESULTING PRESSURE GRADIENT FROM THE RIDGE REMAINING
OVER THE PANHANDLE AND LOW PRESSURE OVER THE YUKON.

 AS THE RIDGE CONTINUES TO TRACK EASTWARD AND WARM FRONTAL BANDS
CROSSING OVER THE REGION STILL EXPECTING A WARM UP FORM WED NIGHT
INTO THURSDAY. SHOULD SEE CENTRAL AND SOUTHERN ZONES BECOME ALL
RAIN OVER NIGHT WITH ONLY THE NORTH ZONES REMAINING MOSTLY SNOW.
COLD AIR LINGERING OVER HAINES WILL KEEP SNOW LONG ENOUGH FOR
ADVISORY LEVEL ACCUMULATION BUT AS THEY TRANSITION TO A RAIN SNOW
MIX EXPECTING AMOUNTS TO BE LOWER THAN WARNING CRITERIA. A LONG
FETCH OF MOISTURE TRACKING UP FROM THE PACIFIC WITH THE JET WILL
PROVIDE AMPLE RAIN FALL FOR THE REGION WHICH WHEN MIXED WITH THE
EXISTING SNOW PACK WILL CAUSE SOME ISSUE WITH DRAINAGE AND WATER
ON ROADWAYS.

 AS THE WARM FRONTAL BANDS AND A 65 KT 850 MB LOW LVL JET TRACK
OVER THE PANHANDLE FROM SOUTH THE NORTH THURSDAY NIGHT WIND GUSTS
ALONG THE SOUTHERN COAST WILL PICK UP TO ADVISORY LEVELS. WIND
GUSTS NEAR POINT ALEXANDER WILL ALSO NEAR ADVISORY LEVELS BUT
WITH THE SOUTHERLY DIRECTION WILL KEPT FROM MOVING INTO THE REST
OF THE ZONE.

 USED A BLEND OF THE NAM12 WITH GFS MIXED IN FOR POP AND
PRECIPITATION AMOUNTS. FORECAST CONFIDENCE IS ONLY FAIR WITH
CHANGES TO THE SNOW LEVEL AND HIGH QPF COULD GET SOME HIGHER SNOW
AMOUNTS OVER THE NORTH CENTRAL REGION.

.LONG TERM...MODELS IN FAIRLY GOOD AGREEMENT ON THE LONG WAVE
PATTERN THROUGH NEXT WEEK. THEY SHOW A SOMEWHAT PROGRESSIVE
PATTERN WITH A SERIES OF TROFS MOVING THROUGH THE AREA OVER THE
NEXT WEEK. THIS WILL KEEP ACTIVE WEATHER GOING OVER THE AREA
DURING THIS TIME...AND TEMPERATURES WILL BE UP AND DOWN THROUGH
THE PERIOD...BUT IT DOES NOT LOOK LIKE ANY EXTREME TEMPS WILL OCCUR.
OF COURSE...THIS WILL MAKE PTYPE FORECAST VERY PROBLEMATIC AS IT
WILL DEPEND ON EXACT TRACK OF SYSTEMS...AND HERE THE MODELS HAVE
SOME DIFFERENCES.

THE MAIN SYSTEM OF CONCERN EARLY IN THE LONG RANGE WILL BE A
DEVELOPING LOW OVER THE ERN GULF LATE THU. MODELS DIFFER SOME ON
THE TRACK/SPEED/STRENGTH OF THE LOW. THE 12Z NAM AND UKMET ALONG
WITH THE 00Z ECMWF WERE CLOSE ON THE TIMING AND TRACK WITH SOME
SMALL DIFFERENCES ON STRENGTH. THE GFS WAS BY FAR THE
STRONGEST...AND UNUSUALLY THE FASTEST MODEL. WENT WITH A 12Z NAM12
AND 00Z ECMWF BLEND FOR THU NIGHT INTO FRI TO HANDLE THIS
LOW...AND THE FOLLOWING TRANSITION TO COLDER AIR MOVING IN FROM
THE W FRI. COULD SEE HEAVY RAIN OVER THE INNER CHANNELS FROM PAJN-
PAOH AREA SWD THU NIGHT. MAY NEED WIND ADVYS FOR MUCH OF THE SAME
AREA AS WELL DURING THAT TIME. ONCE THE LOW JUMPS INLAND EARLY
FRI...COLDER AIR WILL MOVE IN AND TRANSITION PRECIP TO
SHOWERS...BECOMING MAINLY SNOW SHOWERS BY THE AFTERNOON.

FOR THE REMAINDER OF THE PERIOD...FROM FRI NIGHT ONWARD...THE GRIDS
WERE LEFT AS IS DUE TO THE MODEL DIFFERENCES ON INDIVIDUAL SYSTEMS
FURTHER OUT. ADDED IN DAY 8 GRIDS BY USING THE 00Z ECMWF.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT AKST TONIGHT
          FOR AKZ027.
         WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM AKST
          THURSDAY FOR AKZ019.
         WIND ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ018.
MARINE...GALE WARNING FOR PKZ036-041>043-051.
         SMALL CRAFT ADVISORY FOR PKZ012-033>035-052.

PRB/RWT