Small Craft Advisory 211, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1242 PM AKST SAT MAR 5 2011

.SHORT TERM...MORNING SATELLITE IMAGES REVEAL A SLOWLY WEAKENING
LOW IN THE CENTRAL GULF THAT IS DRIFTING TO THE WEST. THE FRONT
ASSOCIATED WITH IT IS CURRENTLY HEADING NORTHWARD THROUGH THE
NORTHERN PANHANDLE SPREADING SNOW AND RAIN SHOWERS AS IT GOES.
WINDS HAVE SIGNIFICANTLY CALMED DOWN SINCE YESTERDAY WITH ONLY A
FEW LOCALIZED BREEZY AREAS LEFT ALONG THE PANHANDLE. THE
EXCEPTIONS ARE SOME OF THE OUTFLOW AREAS LIKE SKAGWAY, LYNN
CANAL, AND CROSS SOUND, WHERE A WIND ADVISORY REMAINS UP AND MIN
GALE TO HIGH SMALL CRAFT WINDS RESPECTIVELY HAVE BEEN BLOWING
MOST OF THE MORNING.

 FOR TONIGHT AND TOMORROW, WINDS WILL CONTINUE TO BE LIGHT TO
BREEZY IN MOST LAND AREAS WITH SMALL CRAFT WINDS IN THE MARINE
AREAS. LYNN CANAL AND SKAGWAY WILL HAVE AN INCREASE IN WIND THIS
EVENING AS A WEAK WAVE MOVES THROUGH LATE TONIGHT. THINKING THAT
WINDS WILL AGAIN BE GUSTING TO 40 MPH OR HIGHER IN SKAGWAY LATE
TONIGHT AND EARLY TOMORROW SO THE WIND ADVISORY REMAINS UP TILL
EARLY TOMORROW. LYNN CANAL WILL AGAIN INCREASE TO GALE FORCE
TONIGHT AS WELL.

 AS FOR PRECIP, SHOWERS WILL BE DIMINISHING THROUGH TONIGHT AND
BY TOMORROW MOST OF THE PRECIP WILL BE CONCENTRATED ALONG A FRONT
THAT WILL STALLED OFFSHORE. HAVE PUT SOME CHANCE POPS ALONG THE
SOUTHERN OUTER COAST TOMORROW AFTERNOON AS THE FRONT MAY MAKE
ENOUGH HEADWAY TO POSE A THREAT FOR PRECIP THERE. FARTHER NORTH
CONTINUED WEAK OUTFLOW WILL KEEP THAT AREA MOSTLY DRY.

 MODEL AGREEMENT WAS VERY GOOD THROUGH THE SHORT TERM. DECIDED TO
USE THE NAM FOR ITS GOOD INITIALIZATION AND ITS DETAILS OVER THE
PANHANDLE. FORECAST CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...MAIN ISSUE IN LONG RANGE IS WHERE THE UPPER HIGH OVER
THE WRN PART OF AK GOES THIS WEEK. IMPORTANCE OF THIS IS WHERE
DOWNSTREAM TROF DEVELOPS. THE GFS IS ON ITS OWN TRYING TO TAKE THE
UPPER HIGH EWD INTO ERN INTR AK BY LATE WEEK...WHILE THE
ECMWF/UKMET/CANADIAN ALL KEEP IT OVER THE FAR WRN PART OF THE
STATE OR EVEN OUT OVER THE BERING SEA. STUCK WITH THE CONSENSUS
SOLUTION OF KEEPING HIGH FURTHER WEST...BUT EVEN THE MINOR DIFFS
AMONGST THE WESTERN SOLUTIONS MAKE A SIGNIFICANT DIFFERENCE. IF
UPPER HIGH SETS UP ALONG OR JUST WEST OF 170W...THE DOWNSTREAM
TROF WILL DEVELOP FURTHER WEST OVER THE GULF...WHEREAS IF THE HIGH
SETS UP CLOSER TO 160-165W...TROF WILL BE FURTHER EAST. THIS COULD
MEAN A DIFFERENCE BETWEEN A WET PATTERN OR A DRY ONE. AT THIS
POINT...WITH HPC USING AN ENSEMBLE APPROACH USED THEIR SOLUTION
FOR THE MIDWEEK PERIOD ON OUT. PRIOR TO THAT USED THE 12Z NAM12 AS
AN EXTENSION TO SHORT RANGE FOR FIRST 24 HRS OF LONG TERM...THEN
DID INCREASING BLEND WITH THE 00Z ECMWF UNTIL THE HPC GRIDS
STARTED AT 12Z WED.

WHAT THESE CHANGES DID IS TO BRING IN A SLIGHTLY BETTER CHANCE FOR
PRECIP OVER THE S SUN NIGHT INTO MON WITH WEAKENING OCCLUDED FRONT
DYING ALONG THE SRN COAST DURING THAT TIME. ALSO MODERATED TEMPS A
BIT ESPECIALLY OVER THE S SUN NIGHT INTO TUE WITH THE OFFSHORE
FLOW SLOWLY WARMING THE LOW LEVEL AIRMASS. DID BRING IN BETTER
PRECIP THREAT MAINLY TO THE S TUE NIGHT INTO WED AS A LOW MOVES
NWD TOWARD THE SE GULF AND THE ASSOCIATED FRONT MOVES IN. EVEN
FURTHER OUT...HAD A GRADUAL NWD SHIFT IN THE PRECIP POTENTIAL FOR
LATE WEEK AS SHOWN BY HPC POP FIELDS. IT DOES LOOK LIKE ANOTHER
SHOT OF COLDER AIR WILL GET INTO THE NRN AREAS WED OR THU BUT IT
DOES NOT LOOK TO BE AS COLD AS IT WAS WITH THIS PAST COLD BLAST.
THIS COLD AIRMASS THOUGH COULD LEAD TO A SNOW EVENT TOWARD LATE
WEEK ONCE UPPER TROF GETS BETTER ESTABLISHED OFFSHORE AND
MID-UPPER LEVEL FLOW BECOMES S-SW. STAY TUNED...

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 5 AM AKST SUNDAY FOR AKZ018.
MARINE...GALE WARNING FOR PKZ011>013-021-022-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ031>036.

&&

EAL/RWT