Small Craft Advisory 213, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
558 AM AKDT MON MAR 19 2012

.SHORT TERM...AN UPPER LEVEL TROUGH OVER SOUTHEAST ALASKA IS
WEAKENING AND EXPECTED TO DISSIPATE BY THIS AFTERNOON. A 983 MB
LOW NEAR 49/145 WILL CONTINUE TO DEEPEN TO AROUND 967 MB AND MOVE
TO JUST WEST OF THE HAIDA GWAII ISLANDS BY 12Z TUE.

 ISOLATED TO SCATTERED SNOW SHOWERS CONTINUING FOR SOUTHEAST
ALASKA THIS MORNING. RADAR INDICATES A BAND OF SHOWERS MOVING
NORTH OF SITKA AND WILL AFFECT CROSS SOUND AREA THIS MORNING. A
SECOND AREA OF SHOWERS IS OVER NORTHERN GLACIER BAY AND SE OF
PAYA THAT APPEARS TO MOVING NORTH AND WEAKENING. THERE IS ALSO A
BAND OF SHOWERS SPREADING NORTH INTO SOUTHERN ZONES ATTM WITH
CLOUD TOP TEMPS FALLING. SINCE SHOWERS ARE NOT MOVING VERY
FAST...LOCATIONS UNDER THESE SHOWERS COULD PICK UP A QUICK INCH
OR TWO. BETWEEN SHOWERS THERE ARE LARGE BREAKS IN CLOUD COVER
THAT WILL LEAD TO SUNNY BREAKS THROUGH THE MORNING.

 BY THIS AFTERNOON EXPECT SHOWERS TO END ACROSS MOST OF SOUTHEAST
ALASKA WITH SCATTERED SHOWERS STILL OVER PAYA AREA. CLOUDS WILL
START TO DECREASE IN THE AFTERNOON ELSEWHERE.

 BY TONIGHT HIGH CLOUDS ASSOCIATED WITH APPROACHING LOW SPREADS
ACROSS SOUTHERN THIRD AND HAVE A CHANCE OF SNOW BY TUESDAY
MORNING. AS THE LOW APPROACHES...THE INNER CHANNELS WILL SEE AN
INCREASING NE PRESSURE GRADIENT. EXPECT NE WINDS TO INCREASE TO
SMCR THROUGH INNER CHANNELS WITH STRONGER WINDS OUT OF INTERIOR
PASSES BY LATE TONIGHT. A GALE IS OUT FOR NORTHERN LYNN CANAL AND
SE GULF BY LATE AFTERNOON. DO HAVE A CRITICAL LEVEL OVER JUNEAU
WITH WIND REVERSAL AROUND 500 MB. THIS COMBINED WITH 40 KT CROSS
BARRIER FLOW EXPECTED TO DEVELOP TAKU WINDS FOR DOWNTOWN
JUNEAU/DOUGLAS AREA LATE TONIGHT.

 LOCATIONS WITH BREAKS IN CLOUD COVER SHOULD BE INTO LOWER 40S
TODAY WHILE THOSE WITH THICKER CLOUDS STAY IN UPPER 30S. WITH
CLEARING SKIES AND CAA IN NE FLOW WILL SEE TEMPS MUCH COLDER
TONIGHT WITH TEENS ACROSS SHELTERED LOCATIONS OF NORTHERN AND
CENTRAL PANHANDLE.

 GOOD MODEL AGREEMENT THROUGH THE SHORT TERM. USED NAM FOR WIND
AND PRES IN GRIDS.

.LONG TERM...THE FORECAST MODELS ARE IN FAIR AGREEMENT THROUGH THE
END OF THE WEEK WITH A UPPER LEVEL TROF PERSISTING OVER THE
GULF. DIFFERENCES SHOW UP OVER THE WEEKEND WITH HOW FAST THE UPPER
TROF DRIFTS TO THE EAST AND THE HIGH AMPLITUDE HIGH OVER THE
BERING MOVES INTO THE GULF. THE GFS IS FASTER WITH THIS TRANSITION
WITH THE EC SLOWER AND AT THE SAME TIME WHEN A WEATHER FRONT MOVES
INTO THE GULF AND OVER THE PANHANDLE THIS WEEKEND. SO WITH THAT
SAID REFRESHED THE LONG RANGE FORECAST WITH THE LATEST HPC WITH A
TREND TOWARDS THE EC ENSEMBLE MEAN AND GEFS SOLUTIONS. THERE IS
ABOUT AVERAGE FORECAST CONFIDENCE FOR THE END OF THE WEEK INTO THE WEEKEND.

AT THE BEGINNING OF THE LONG RANGE PERIOD A VERTICALLY STACKED
WEAKENING SURFACE LOW WILL BE OVER HAIDA GWAII. THIS LOW WILL
SLOWLY TRACK NORTH AND CONTINUE TO WEAKEN OVER THE SOUTHERN
PANHANDLE. A WEAK BROAD AREA OF LOW PRESSURE WILL PERSIST OVER THE
GULF THROUGH THE WEEK WITH MOST PRECIP FALLING OVER THE SOUTHERN
AREAS AND THE NORTHERN AREAS ON THE DRY SIDE. THE LATEST EC AND
NAM RUNS HAVE LIMIT THE AMOUNT OF PRECIP OVER THE FAR SOUTHERN
AREAS TUE MORNING WITH SIGNIFICANT DEEP EASTERLY FLOW. AS THE UPPER
LEVEL DYNAMICS LIFTS OVER THE FAR SOUTHERN AREAS PRECIP WILL
DEVELOP TUE AFTERNOON AND SHOULD BE IN THE FORM OF SNOW WITH
COOLER DEW POINTS FROM THE EASTERLY FLOW. AMOUNTS WILL NOT BE THAT
SIGNIFICANT BUT COULD ADD UP TO A FEW INCHES. THERE IS SOME WARMER
AIR AT THE CORE OF THE LOW THAT THE FAR SOUTHERN AREAS WILL MIX
WITH RAIN THROUGH TUE NIGHT AND INTO WED. CHANCE PRECIP WILL
PERSIST OVER THE SOUTHERN AREAS WITH MORE ONSHORE FLOW. THE
NORTHERN HALF OF THE AREA WILL BE ON THE DRY SIDE WITH OFFSHORE
FLOW.

WIND WISE...THERE WILL BE SOME STIFF WINDS FROM THE NORTH OVER THE
INNER CHANNELS WITH GALES OVER THE NORTHERN LYNN AND SMALL CRAFT
OVER THE REST OF THE INNER CHANNELS AND EASTERN GULF TUE MORNING.
THE LAND AREAS WILL SEE LOCALLY WINDY CONDITIONS IN EXPOSED AREAS
ESPECIALLY NEAR INTERIOR GAPS AND OVER THE FAR SOUTHERN AREAS. THE
DOWNTOWN JUNEAU AREA WILL SEE A WEAK TAKU WIND EVENT WITH GUSTS TO
45 MPH. THESE STRONG WINDS WILL CONTINUE FROM EARLY TUE MORNING
INTO TUE EVENING BEFORE DECREASING AS THE CROSS BARRIER FLOW
RELAXES. AS THE LOW WEAKENS THROUGH TUE THE STRONG WINDS FROM THE
NORTH A GUSTS FROM INTERIOR PASSES WILL BEGIN TO DIMINISH THROUGH
LATE TUE AFTERNOON AND CONTINUE TO DECREASE THROUGH TUE NIGHT. BY
WED MOST AREAS WILL SEE RELATIVELY LIGHT WINDS WITH THE STRONGEST
WINDS OVER THE NORTHERN INNER CHANNELS.

USED MAINLY THE EC FROM TUE MORNING THROUGH WED NIGHT AS IT HAS
BEEN THE BEST FROM RUN TO RUN WITH THE LOW LIFTING OVER THE
PANHANDLE. THERE IS ABOVE AVERAGE FORECASTER CONFIDENCE IN THE MID RANGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR
     AKZ025.
MARINE...GALE WARNING FOR PKZ012-041.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031>036-042-043-053.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051.

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