Small Craft Advisory 207, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
603 AM AKDT WED MAR 14 2012

.SHORT TERM...QUIET NIGHT ACROSS THE PANHANDLE THIS MORNING.
MAIN WEATHER CONCERNS AT THE MOMENT ARE THE SHOWERS DRIFTING
THROUGH THE PANHANDLE. MOST ARE WIDELY SCATTERED BUT THERE IS ONE
SEMI- ORGANIZED BAND MOVING NORTH THROUGH THE SOUTHERN PANHANDLE
AT THE MOMENT ASSOCIATED WITH A MID LEVEL VORT MAX. FOR MOST
PLACES THESE SHOWERS HAVE BEEN IN THE FORM OF SNOW AS SURFACE
TEMPS HAVE BEEN COLD ENOUGH TO SUPPORT IT. ANY ACCUMULATIONS HAVE
BEEN LESS THEN 1 INCH WITH ISOLATED AREAS UNDER HEAVIER SHOWERS
GETTING A QUICK INCH OR TWO.

FOR TODAY AND TONIGHT SHOWERS WILL DIMINISH OVER THE NORTHERN
HALF OF THE PANHANDLE AS EASTERLY DOWNSLOPING FLOW AHEAD OF THE
NEXT WEAKENING LOW DRYS OUT THE AREA. THIS SHOULD ALSO ALLOW FOR
BREAKS TO FORM IN THE CLOUD COVER AND MAY OFFER PARTLY CLOUDY
SKIES FOR BRIEF PERIODS TODAY. THE SOUTHERN HALF OF THE PANHANDLE
WILL BE AFFECTED BY A WEAKENING LOW COMING NORTH THIS AFTERNOON.
HAVE KEPT CATEGORICAL POPS FOR TODAY AND LIKELY POPS FOR TONIGHT
FOR THE SOUTHERN PANHANDLE AS THIS SYSTEM SPREADS MORE SHOWERS AND
A WEAK NARROW FRONTAL BAND OVER THE AREA. MOST AREAS THIS
AFTERNOON AND EVENING WILL BE WARM ENOUGH THAT THE PRECIP WILL
EITHER FALL AS RAIN OR THE SNOW WILL MELT ONCE IT HITS THE GROUND
SO ACCUMULATIONS SHOULD BE LIGHT. THE PRECIP WILL SPREAD NORTH
THROUGH THE NIGHT BUT AGAIN THE EASTERLY FLOW WILL LIMIT AMOUNTS
AND HOW WIDESPREAD THE SHOWERS ARE THE FARTHER NORTH THEY VENTURE.

THE OTHER DETAIL THAT NEEDS LOOKING AT IS THE WIND THIS SYSTEM
WILL BE SPREADING ACROSS THE EXTREME SOUTHERN AREA. PRESSURE
PATTERN SUGGESTS THAT INITIALLY THE WIND WILL BE FROM AN EASTERLY
DIRECTION WED WHICH WILL LIMIT THE STRONGER WINDS TO EASTERLY
EXPOSURES. THE HIGHER WINDS WILL NOT BEGIN TO SPREAD TO KETCHIKAN,
HYDABURG, AND UP CLARENCE STRAIT UNTIL THE LOW GETS FAR ENOUGH UP
THE COAST THAT THE PRESSURE PATTERN FAVORS MORE SE FLOW. THAT WILL
NOT HAPPEN UNTIL AT LEAST LATE AFTERNOON AND BY THEN I THINK THAT
THE SYSTEM WILL HAVE WEAKENED ENOUGH THAT STRONG WIND HEADLINES
WILL NOT BE NEEDED BUT GUSTY WINDS WILL STILL BE POSSIBLE INTO THE
EVENING HOURS. FARTHER NORTH THE PRESSURE GRADIENT WILL BE
TIGHTENING UP AGAIN AS THIS SYSTEM MOVES NORTH. NORTHERLY SMALL
CRAFT WINDS WILL ONCE AGAIN BE BLOWING IN LYNN CANAL STARTING THIS
EVENING AND CONTINUING THROUGH THE NIGHT.

SHORT RANGE MODELS ARE IN DECENT AGREEMENT AS THEY BRING THE LOW
NORTH BUT THE GFS WAS SUGGESTING SOMETHING A LITTLE TOO FAR TO THE
WEST COMPARED TO THE REST OF THE MODELS. DECIDED TO STICK WITH THE
NAM FOR SHORT RANGE UPDATES DUE TO GOOD INITIALIZATION AND
CONSISTENCY. FORECAST CONFIDENCE IS A LITTLE ABOVE AVERAGE.

&&

.LONG TERM...JET STREAM IS FORECAST TO STAY SOUTH OF THE FORECAST
ARE THROUGH THE LONG TERM. A MEAN NEGATIVELY TILTED UPPER TROUGH
WILL DRIFT FROM THE WESTERN GULF FRIDAY ACROSS SOUTHEAST ALASKA BY
EARLY NEXT WEEK. A SHARP HIGH AMPLITUDE RIDGE IS FORECAST TO BUILD
INTO THE BERING BY NEXT TUESDAY WHICH ALLOWS A COLD UPPER LOW TO
DEVELOP OVER THE GULF MID WEEK.

A 978 MB LOW MOVES THROUGH EASTERN GULF THURSDAY AND PULLS BACK TO
THE NW BY THURSDAY NIGHT. THE LOW THEN SLOWLY FILLS ACROSS
NORTHWEST GULF INTO WEEKEND. THE ASSOCIATED FRONT WEAKENS AS IT
LIFTS NORTH THROUGH SOUTHEAST ALASKA THURSDAY/THU NIGHT. WITH NEGATIVE
TILT EXPECT MOST PRECIP ACROSS SOUTHERN WITH WEAK DOWN SLOPE
THROUGH NORTHERN PANHANDLE. OVERALL DON'T EXPECT VERY MUCH PRECIP
AS FRONT MOVES THROUGH QUICKLY AND WEAKENS BUT WILL HAVE JUST ENOUGH
COLD AIR IN ADVANCE OF THIS SYSTEM FOR PRECIP TO BE MIXED WITH
SNOW. NORTHERN INNER CHANNELS WILL INCREASE TO NLY SMCR WHILE SRN
INNER CHANNELS GO TO SE SMCR POST FRONTAL.

UPPER TROUGH WILL MOVE THROUGH OVER THE WEEKEND AND BRING PERIODS
OF LIGHT PRECIP. AGAIN TEMPS REMAIN MARGINAL IN CAA FROM WEST TO
SEE A MIX OF SNOW AND RAIN BUT AMOUNTS NOT EXPECTED TO BE VERY MUCH.

KEEPING A COOL AND FAIRLY DRY FORECAST FOR NEXT WEEK BUT STILL
WILL HAVE SEVERAL DISTURBANCES ROTATE NORTHWARD AND COULD BRING
PRECIP BACK INTO SOUTHERN PANHANDLE BY EARLY NEXT WEEK.

MODELS IN FAIR AGREEMENT THROUGH 120 HRS BEFORE FAIRLY LARGE
DIFFERENCES APPEAR IN TIMING AND POSITION AFTER 144 HRS. USED NAM
TO 84 HRS AND A GFS/EC BLENDS THROUGH DAY 5. USED HPC GRIDS AFTER
DAY 5.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ011>013-021-022-031>036-041>043-051-
     052.

&&

EAL/MM