Small Craft Advisory 189, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
417 PM AKST WED MAR 7 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
UNDER CLOUDY SKIES WITH A DEVELOPING LOW LIFTING NORTH OUT OF THE
NORTH PACIFIC. A WARM FRONT IS LIFTING OVER THE PANHANDLE THIS
AFTERNOON AND PRODUCING RAIN OVER MOST OF THE SOUTHERN TWO
THIRDS. THERE ARE A FEW EXCEPTIONS LIKE THE PAPG AREA ALONG WITH
THE MENDENHALL VALLEY AS THEY ARE MIXED RAIN AND SNOW BUT DO
EXPECT THESE AREAS TO TURN ALL RAIN THROUGH THE EVENING HOURS AS
THE WAA CONTINUES. RAIN WILL BECOME HEAVY AT TIMES OVER THE
SOUTHERN AREA ALONG WITH THE COASTAL AREA THROUGH WED WITH GOOD
UPPER LEVEL DYNAMICS ALONG WITH VERTICAL LIFT. AS THE LOW LIFTS
INTO THE CENTRAL GULF BY WED AFTERNOON THE WINDS OVER THE GULF
WILL INCREASE TO GALES FROM THE SE ALONG WITH GALES OVER CLARANCE
STRAIT AND CROSS SOUND BY THE AFTERNOON. THERE IS A STRONG 70KT
LLJ SO STRONG WINDS GUSTS TO DEVELOP OVER THE FAR SOUTHERN
COASTAL AREA WED AFTERNOON AND SPREAD INTO REST OF THE SOUTHERN
HALF BY THE AFTERNOON. MARINE WINDS OVER THE INNER CHANNELS WILL
SLOWLY INCREASE TO SMALL CRAFTS THROUGH TONIGHT WITH THE
EXCEPTION OF LYNN CANAL AS THEY WILL BE BECOMING A LIGHT NORTH OR
VARIABLE. THEY WILL SLOWLY INCREASE THROUGH WED WITH A SOUTHERLY
850MB FLOW WITH SOUTHERN LYNN INCREASING TO SMALL CRAFT FROM THE
SOUTH.

 THERE ARE SOME AREAS THAT ARE COLDER THIS AFTERNOON LIKE THE FAR
NORTHERN INNER CHANNELS ALONG WITH THE NORTH GULF COAST. THESE
AREAS WILL CONTINUE TO SEE SNOW THROUGH MID DAY ON WED AS THEY
WILL KEEP WINDS FROM THE INTERIOR TO KEEP THE COLD AIR IN PLACE.
SO WITH THAT SAID CONTINUED THE WINTER STORM WARNING FOR THE
NORTHERN INNER CHANNELS AND UPGRADED THE WWA FOR ZONE 17 TO A
WARNING. THE PAYA AREA LOOKS TO KEEP A EASTERLY SURFACE WIND
THROUGH THE AFTERNOON WITH A STRONG SE WINDS AT 850 TO INCREASE
THE MOISTURE TRANSPORT BUT BY THE AFTERNOON THE AIR TEMP MAY GET
ABOVE FREEZING TO LIMIT MUCH MORE SNOW ACCUMULATIONS BUT
6-8 INCHES LOOKS GOOD. FOR THE PAHN AND PAGY AREA THE WINDS WILL
BE LIGHT FROM THE NORTH THROUGH MOST OF THE TIME FRAME. WITH
STRONG WAA THEY WILL MIX WITH RAIN IN THE EARLY AFTERNOON NEAR
SEA LEVEL BUT KEEP SNOWING ALONG THE BORDER AND NEAR WHITE PASS.
SO WITH THAT SAID THE LARGEST SNOW ACCUMULATIONS WILL BE AT
HIGHER ELEVATIONS WITH UP TO 15 INCHES.

 USED A BLEND OF THE PREVIOUS FORECAST AND THE 12Z NAM/GFS FOR THE
NEXT 24HRS. THERE IS ABOUT AVERAGE FORECASTER CONFIDENCE.

&&

.LONG TERM...LITTLE IN THE WAY OF CHANGES FOR THE EXTENDED RANGE
FORECAST PERIOD. A FRONT AFFECTING SOUTHEAST ALASKA IN THE SHORT
TERM PERIOD WILL STILL BE IN PLACE AND PRODUCING SNOW/RAIN AT THE
BEGINNING OF THE LONG RANGE. WILL ALSO STILL HAVE STRONG WINDS
ALONG THE OUTER COAST SOUTH OF CAPE DECISION THURSDAY EVENING. AN
ABRUPT WIND SHIFT ASSOCIATED WITH FRONTAL PASSAGE WILL SEE
SOUTHEAST GALE REPLACED BY SOUTHWEST GALES ALONG THE OUTER COAST
THURSDAY NIGHT WHICH SHOULD PRODUCE EXTREMELY CHOPPY SEAS IN THE
COASTAL MARINE ZONES WITH WAVE HEIGHTS RANGING FROM 12 TO 20 FEET.
STORM SURGE IS A BIT OF A CONCERN THURSDAY AFTERNOON WITH HIGH
TIDE OCCURRING NOT TOO LONG BEFORE FRONTAL PASSAGE AND A FULL
MOON. CURRENTLY, STORM SURGE FORECAST ARE BELOW MAXIMUM
ASTRONOMICAL TIDE LEVELS, BUT NOT BY MUCH. JUNEAU, ELFIN COVE, AND
SITKA ALL FORECAST TO BE WITHIN 1 FOOT OF MAT. SITUATIONS LIKE
THIS IN THE PAST HAVE RESULTED IN DRIFTWOOD AND OTHER MARINE
DEBRIS WASHING OVER THE RUNWAY AT SITKA.

SNOW AMOUNTS ASSOCIATED WITH THE THURSDAY NIGHT FRONT NOT FORECAST
TO EXCEED ADVISORY LEVELS ANYWHERE, AS WEAK WARM AIR ADVECTION
SHOULD ARRIVE LATE AT NIGHT AND PREVENT SNOW LEVELS FROM FALLING
VERY FAR OVERNIGHT. BY THE TIME THE WARM AIR ADVECTION RUNS OUT,
PRECIPITATION WILL BE WINDING DOWN. POP REMAINS HIGH, THOUGH, AND
A SECOND FRONT ARRIVES ALONG THE OUTER COAST FRIDAY NIGHT. WARM
ADVECTION SHOULD ONCE AGAIN PREVENT ANY ADVISORY LEVEL SNOW
ACCUMULATIONS, BUT DO HAVE UP TO 3 INCHES FOR SOME LOCATIONS
FRIDAY NIGHT INTO SATURDAY MORNING. A POST FRONTAL TROUGH ON
MONDAY WILL KEEP POPS HIGH INTO THE BEGINNING OF NEXT WEEK AND A
FRONT WILL APPROACH THE PANHANDLE FROM THE SOUTH BY MID WEEK.

USED GFS THROUGH THE MID RANGE AND BLENDED IN HPC DAYS 5 THROUGH
8. FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THURSDAY AFTERNOON FOR AKZ023-026-028.
         STRONG WIND FROM THURSDAY MORNING THROUGH THURSDAY AFTERNOON FOR
     AKZ027.
         WINTER STORM WARNING UNTIL NOON AKST THURSDAY FOR AKZ019.
         WINTER STORM WARNING UNTIL NOON AKST THURSDAY FOR AKZ018.
         WINTER STORM WARNING FROM 1 AM TO NOON AKST THURSDAY FOR AKZ017.
MARINE...GALE WARNING FOR PKZ022-033-035-036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ013-021-032-034-051>053.

&&

ABJ/FRITSCH