Storm Warning 33, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
618 AM AKST FRI MAR 4 2011

.SHORT TERM...A 990 MB LOW IS ENTERING THE EXTREME SOUTHEASTERN
GULF WITH A VERY IMPRESSIVE BAROCLINIC CLOUD SHIELD. THIS
LOW...IN CONJUNCTION WITH STRONG HIGH PRESSURE OVER WESTERN
CANADA...WILL CAUSE A RESUMPTION OF STRONG NORTHEASTERLY OUTFLOW
WINDS DURING THE SHORT TERM FORECAST PERIOD. THE MAXIMUM PRESSURE
GRADIENT WILL MIGRATE FROM SOUTH TO NORTH THROUGH TONIGHT WITH
MAXIMUM INTENSITY WINDS OCCURRING FROM LATE THIS AFTERNOON
THROUGH THE EARLY MORNING ON SATURDAY. HAVE WIND ADVISORIES
AND/OR WINTER WEATHER ADVISORIES OVER ALL THE SOUTHEAST ALASKA
FORECAST ZONES IN RESPONSE TO THIS. ADDITIONALLY...HAVE REPLACED
THE HIGH WIND WATCH FOR JUNEAU WITH A HIGH WIND WARNING FROM 9 AM
FRIDAY MORNING THROUGH AT LEAST 5 AM SATURDAY MORNING. HAVE
ALREADY SEEN ADVISORY LEVEL GUSTS IN DOWNTOWN JUNEAU AS OF EARLY
THIS MORNING.

THE OTHER ISSUE IN THE SHORT RANGE FORECAST PERIOD RELATED TO
THIS LOW WILL BE PRECIPITATION. HAVE KEPT THE WINTER WEATHER
ADVISORIES ALREADY IN PLACE WITH SOME ADJUSTMENTS TO START AND
STOP TIMES. HAVE ALSO ADDED HOONAH AND ANGOON. IN GENERAL...AM
LOOKING AT A 3 TO 5 INCH SNOW EVENT ACROSS SOUTHEAST ALASKA WITH
ADVISORY LEVEL AMOUNTS FOR HOONAH AND ANGOON PLUS LOCATIONS SOUTH
OF FREDERICK SOUND AND LESSER AMOUNTS ELSEWHERE. HAVE SOME
CONCERNS ABOUT SNOW TOTALS OVER THE FAR SOUTHWESTERN PORTION OF
THE PANHANDLE. ADJUSTMENTS MADE TO DAYTIME HIGH TEMPS FOR TODAY
SUGGEST THAT PRECIP TODAY COULD BECOME MIXED BY THE AFTERNOON AND
NOT SWITCH BACK OVER TO STRAIGHT SNOW UNTIL THIS EVENING. THIS
WOULD HAVE A NEGATIVE IMPACT ON STORM TOTAL SNOW AMOUNTS. DECIDED
TO KEEP THE SNOW ACCUMULATIONS UP TO ADVISORY LEVELS AND MENTION
THE POSSIBILITY OF MIXED PRECIP THIS AFTERNOON AND EVENING RATHER
THAN CANCEL AN ADVISORY THAT WAS SET UP VERY WELL BY DAY SHIFT
YESTERDAY.

USED NAM FOR UPDATES TO THE SHORT TERM FORECAST. INCLUDED SOME
WRF WINDS OVER DOWNTOWN JUNEAU TO ACCOUNT FOR EXPECTED HIGH WIND
EVENT. DID NOT INCLUDE ANY WRF WINDS OVER ZONE 17 EAST OF YAKUTAT
AS THEY APPEARED TO BE SOMEWHAT OVERDONE. FORECAST CONFIDENCE IS
ABOVE AVERAGE.

&&

.LONG TERM...985 MB LOW IN EASTERN GULF TURNS NW ON SATURDAY AND
WEAKENS. THE ASSOCIATED FRONT WILL BE OVER THE NORTHERN PANHANDLE
BUT BECOMES SHEARED APART BY MID DAY. A SECOND WRAP OF THE
OCCLUSION WILL PUSH INTO THE SOUTHEAST GULF AND SPREAD A MIX OF
RAIN AND SNOW THERE. E-NE WINDS DIMINISH THROUGH THE DAY.

BY SUNDAY HIGH PRESSURE OVER THE YUKON BECOMES DOMINATE AGAIN AND
EXPECT DRY COLD CONDITIONS THROUGH NEXT WEEK. WILL HAVE NORTHERLY
OUTFLOW GALES BUT NOT NEARLY AS STRONG AS LAST WEEK.

A SECOND FRONT MOVES INTO THE GULF BY TUESDAY BUT BECOMES
STATIONARY. A LOW FORECAST TO DEVELOP ON THE FRONT DIGS SE AND
STRETCHES THE FRONT AND IT FALLS APART OVER THE WATER. THIS WILL
BRING SOME CLOUDS TO SOUTHERN ZONES.

AS AGREED WITH AFC USED EC FOR GRIDS THROUGH SUNDAY TO CAPTURE
STRONGER WINDS IN WESTERN GULF. BIG DIFFERENCES BETWEEN GFS AND EC
PRESSURE FOR SYSTEMS SOUTH OF ALEUTIANS SO CONFIDENCE WAS BELOW
AVERAGE AND OPTED TO MAKE NO CHANGES AFTER.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 9 PM AKST THIS EVENING FOR AKZ026-
     027.
         WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 5 AM AKST
     SATURDAY FOR AKZ021-024.
         HIGH WIND WARNING UNTIL 5 AM AKST SATURDAY FOR AKZ025.
         WIND ADVISORY UNTIL 5 AM AKST SATURDAY FOR AKZ017-019-020-022-
     023-029.
         WINTER WEATHER ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ028.
         WINTER WEATHER ADVISORY UNTIL 5 AM AKST SATURDAY FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011-012-031.
         HEAVY FREEZING SPRAY WARNING FOR PKZ013.
         HEAVY FREEZING SPRAY WARNING FOR PKZ013.
         STORM WARNING FOR PKZ011>013-022-043.
         GALE WARNING FOR PKZ021-031>036-041-042-051-052.

&&

FRITSCH/MM