Small Craft Advisory 606, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
313 PM AKDT THU OCT 18 2012

.SHORT TERM...AFTERNOON SATELLITE IMAGERY SHOWS A BROAD LOW
PRESSURE SYSTEM CONTINUING TO SPIN IN THE NORTHERN GULF. AN
EMBEDDED MESOSCALE LOW WITHIN THIS BROAD LOW IMPACTED THE YAKUTAT
AREA WITH BANDS OF MODERATE TO HEAVY SNOW THIS MORNING AND
AFTERNOON. THIS FEATURE IS CURRENTLY WEAKENING AS IT PUSHES
INLAND ALONG THE NORTHERN COAST. COLD AIR ALOFT WRAPPING AROUND
THE BROAD LOW IN THE GULF HAS PRODUCED WIDESPREAD SHOWERS OVER THE
GULF AND SOUTHEAST ALASKA FOR MUCH OF THE DAY. THERE HAS BEEN A
NOTICEABLE DECREASE IN SHOWER ACTIVITY THIS AFTERNOON AS THE LOW
BEGINS TO GRADUALLY DRIFT TO THE SOUTHEAST. AS THIS LOW SLOWLY
MOVES TO THE SOUTHEAST GULF ON FRIDAY AFTERNOON...SHOWER ACTIVITY
WILL DECREASE FROM NORTH TO SOUTH TONIGHT INTO FRIDAY.

 THE FLIP TO A NORTHERLY PRESSURE GRADIENT HAS BEEN A BIT DELAYED
FROM PREVIOUS THINKING. WINDS ACROSS THE INNER CHANNELS AND LAND
AREAS REMAIN OUT OF THE SOUTH LATE THIS AFTERNOON WITH SMALL
CRAFT WINDS IN NORTHERN LYNN CANAL AND GUSTY SOUTH WINDS IN
SKAGWAY AND HAINES. WINDS WILL SHIFT TO THE NORTH LATE THIS
EVENING ACROSS THE NORTHERN INNER CHANNELS AND INCREASE THROUGH
THE DAY ON FRIDAY. WINDS WILL REACH SMALL CRAFT LEVELS BY LATE
FRIDAY AFTERNOON IN THIS AREA. THESE NORTHERLY AND EASTERLY WINDS
WILL DEVELOP ACROSS THE SOUTHERN AREAS DURING THE DAY FRIDAY.
GUSTS WILL ALSO BEGIN TO DEVELOP OUT OF INTERIOR PASSES BEGINNING
FRIDAY AFTERNOON.

 AS NORTHERLY WINDS DEVELOP AND COLDER AIR BEGINS TO SLOWLY
FILTER INTO THE NORTHERN INNER CHANNELS LATE TONIGHT...EXPECT
THAT SHOWERS WILL MIX WITH SNOW. ACCUMULATION WILL BE CONFINED TO
KLONDIKE AND HAINES HIGHWAYS WITH LESS THAN 1 INCH ANTICIPATED.

 USED A BLEND OF THE EC/NAM FOR THE SHORT TERM PERIOD. FORECASTER
CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...LOOKS LIKE A FAIRLY QUIET WEATHER PATTERN FOR THE
AREA ESPECIALLY THIS WEEKEND INTO EARLY NEXT WEEK. HIGH PRESSURE
WILL BE BUILDING OVER SE INTERIOR AK AND NW CANADA...WHILE A LOW
OVER THE FAR SE GULF SLOWLY DRIFTS TO THE SE. THERE WILL BE A
TROF THAT EXTENDS NW ALONG THE OUTER COAST SUN INTO MIDWEEK...AND
A COMBINATION OF THIS TROF AND THE HIGH TO THE NORTH WILL KEEP AN
OFFSHORE FLOW OVER THE AREA. THERE ARE SOME MODEL DIFFERENCES ON
FEATURES ALOFT THAT MAY IMPACT CLOUD COVER SAT INTO MON...WITH
THESE SYSTEMS GENERALLY ONLY HAVING HIGH TO MID-LEVEL CLOUDS
MOVING IN FROM THE NE. PREFERRED THE 00Z EC APPROACH TO THESE
FEATURES ALOFT AS IT WAS SUPPORTED BY THE 12Z UKMET AND TO A
LESSER EXTENT THE NAM.

 MAIN ADJUSTMENT MADE TO THE FORECAST WAS TO BUMP UP MAX TEMPS
ESPECIALLY OVER THE NORTHERN AREAS THROUGH LATE NEXT WEEK. WHILE
COOLER AIR IS EXPECTED TO MOVE IN...COMBINATION OF LITTLE TO NO
SNOW COVER...GOOD MIXING BY WINDS...AND LATE OCTOBER SUNSHINE
SHOULD KEEP DAYTIME TEMPS FROM REMAINING BELOW FREEZING...EVEN
OVER MOST OF THE FAR NORTH. THE NIGHTTIME TEMPS WILL BE TRICKIER
AS THEY WILL DEPEND MORE ON HOW MUCH WIND THERE IS ESPECIALLY
NEXT WEEK. STILL LOOKS LIKE MOST AREAS SHOULD DROP WELL BELOW
FREEZING THOUGH AT NIGHT.

 WITH MODELS DIFFERING ON FEATURES BY MIDWEEK...THOUGHT THE HPC
ENSEMBLE APPROACH WAS GOOD...SO ENDED UP USING LATEST HPC FROM
MON INTO LATE WEEK. ALL IN ALL...A FAIRLY TRANQUIL WEATHER
PATTERN FOR THE AREA OTHER THAN SOME LOCALLY WINDY CONDITIONS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-013-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041>043.

&&

TPS/RWT