Winter Storm Watch 8, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
414 PM AKST TUE MAR 6 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
UNDER CLOUDY SKIES AS A WARM FRONT MOVES ACROSS THE REGION. MOST
STATIONS ATTM ARE REPORTING PRECIP WITH DEEP ONSHORE FROM THE SW
AT MOST LEVELS. P-TYPE HAS BEEN TRICKY WITH THE SE WINDS OVER THE
INNER CHANNELS AND WAA. MOST PLACES OVER THE COASTAL AND SOUTHERN
AREAS HAVE CHANGED OVER TO RAIN WITH SOME ISOLATED AREAS OF
MIXED. OVER THE NORTHERN INNER CHANNELS THERE IS A MIX OF RAIN
AND SNOW BUT THERE IS SOME AREAS THAT ARE STILL SNOW. MOST AREAS
WILL TURN ALL OVER TO RAIN THROUGH THE LATE AFTERNOON/EARLY
EVENING HOURS AS THE WARM AIR CONTINUE TO MOVE OVER THE AREA FROM
THE SW. SO WITH THAT WILL EXPIRE ALL WINTER WEATHER PRODUCTS THIS
AFTERNOON. THE RAIN WILL CONTINUE OVER MOST OF THE FORECAST AREA
THROUGH TONIGHT BUT THERE IS AN AREA OF DRIER CONDITIONS MOVING
OVER THE NORTHERN GULF ATTM. THIS AREA WILL DRIFT OVER THE FAR
NORTHERN AREAS ALONG WITH SOME COOLER AIR THAT WILL DIMINISH THE
THREAT OF PRECIP SOME AND IT MAY BE IN THE FROZEN FORM. WITH
ATMOSPHERE BEING VERY STABLE THERE WILL BE LOW CLOUD COVER ALONG
WITH POSSIBLE AREAS OF FOG ALONG THE COASTAL AND LOCAL AREAS OF
INNER CHANNELS.

 THE WINDS CONTINUE TO BE ON THE GUSTY SIDE AS THE PRESSURE
GRADIENT WILL BE ON THE TIGHT SIDE WITH THE LEE SIDE LOW OVER THE
YUKON AND THE RIDGE OVER SE AK. THE LOW OVER THE YUKON WILL
SLOWLY SLIDE TO THE EAST AND THE PRESSURE GRADIENT WILL RELAX
THROUGH TONIGHT. SO WITH THAT SAID THE GALES OVER NORTHERN LYNN
AND THE SMALL CRAFT OVER THE REST OF THE NORTHERN INNER CHANNELS
WILL DIMINISH TO RANGE FROM 15 TO 20 KT. THE WINDS OVER THE
SOUTHERN AREAS WILL INCREASE SOME TONIGHT AS RIDGE WILL PERSIST
AND THE WINDS WILL REMAIN NEAR THE SMALL CRAFT RANGE.

 FOR WED...THE DEEP SW FLOW WILL PERSIST ALONG WITH THE SURFACE
RIDGE OVER THE FORECAST. THE PRECIP WILL REMAIN CATEGORICAL OVER
THE SOUTHERN TWO THIRDS WITH CHANCES OVER THE NORTHERN AREAS. THE
WARM AIR WILL BEGIN TO DRIFT NORTH AND IN DOING SO INCREASE THE
THREAT OF PRECIP OVER THE NORTHERN AREAS BUT PAYA WILL REMAIN ON
THE DRY SIDE. THE SURFACE RIDGE WILL KEEP THE SOUTHERN WINDS
GOING AND WILL RANGE FROM 35 KT OVER CLARENCE TO 15 KT NEAR
GLACIER BAY.

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

&&

.LONG TERM...EXTENDED RANGE FORECAST BEGINS WITH A LOW AND WELL
ORGANIZED FRONT APPROACHING THE PANHANDLE FROM THE SOUTHWEST.
THICKNESS PATTERN INDICATES THAT THE OCCLUSION WILL REMAIN
OFFSHORE THROUGH AT LEAST THURSDAY MORNING, SO FRONTAL PASSAGE
OVER SOUTHEAST ALASKA SHOULD BE A TRUE WARM FRONT. ADJUSTED SNOW
LEVELS UP A BIT IN RESPONSE. IN SPITE OF THIS, STILL HAVE SNOW IN
THE FORECAST WEDNESDAY NIGHT FOR JUNEAU AND LOCATIONS NORTH OF A
LINE FROM ANGOON TO SITKA. SNOW TOTALS AROUND 2 INCHES OR LESS,
BUT QPF VALUES ASSOCIATED WITH THIS FRONT ARE QUITE HIGH, SO MINOR
CHANGES TO TEMPS AND SNOW LEVELS COULD PRODUCE SIGNIFICANT SNOW
TOTAL CHANGES. AS IT IS, HAVE RAIN HEAVY AT TIMES FOR THE SOUTHERN
HALF OF THE PENINSULA.

PRESSURE GRADIENT IN ADVANCE OF THE FRONT QUITE STRONG, SO AM
EXPECTING STRONG WIND HEADLINES ALONG THE OUTER COAST FROM CAPE
SPENCER SOUTH TO THE DIXON ENTRANCE THURSDAY THROUGH THURSDAY
NIGHT. SOUTHEAST GALES OVER THE COASTAL MARINE ZONES IN ADVANCE OF
THE FRONT FOLLOWED BY POST FRONTAL SOUTHWEST GALES.

THE NEXT FRONT WILL ARRIVE ALONG THE OUTER COAST FRIDAY NIGHT. A
COLDER LOW LEVEL AIRMASS WILL BE IN PLACE FOR THIS SYSTEM AND THE
WARM SECTOR NOT NEARLY AS PRONOUNCED, SO HIGHER PROBABILITY FOR A
SIGNIFICANT SNOW EVENT GOING INTO THE WEEKEND. SOUTHEASTERLY GALES
OVER THE COASTAL MARINE ZONES IN ADVANCE OF THIS FRONT AS WELL,
BUT LIMITED TO THOSE MARINE ZONES SOUTH OF CAPE EDGECUMBE.

EXCELLENT RUN-TO-RUN CONSISTENCY IN GFS, WHICH WAS THE PREFERRED
SOLUTION BY HPC AS WELL. FORECAST HEAVILY WEIGHTED TOWARDS GFS
THROUGH FRIDAY NIGHT, THEN EQUALLY BLENDED WITH HPC FOR PRESSURE
THROUGH MONDAY. FORECAST CONFIDENCE IS AVERAGE TO SLIGHTLY ABOVE
AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 3 PM AKST THIS AFTERNOON FOR
     AKZ018-019-026.
         WINTER STORM WARNING UNTIL 3 PM AKST THIS AFTERNOON FOR AKZ025.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-036.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031>035-041>043-051-
     052.

&&

ABJ/FRITSCH