Gale Warning 461, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1243 PM AKST THU DEC 25 2008

.SHORT TERM...CHRISTMAS MORNING SATELLITE LOOP SHOWS INCREASING
CLOUDS ACROSS THE NORTHERN PANHANDLE WITH ABUNDANT MOISTURE
RIDING OVER THE TOP OF A WEAKENING RIDGE IN THE CENTRAL GULF.
WINDS ARE GENERALLY LIGHT ACROSS THE LOCAL REGION WITH
UNRESTRICTED VISIBILITIES. BIORKA RADAR WORKS FINE BUT NO SIGN OF
SANTAS COMING FROM THE NORTH. MODELS ARE IN FAIR AGREEMENT WITH
AN UPPER LEVEL SHORTWAVE MOVES INTO THE NORTHERN GULF TONIGHT AND
ENHANCES A SURFACE GALE FORCE LOW...PUSHING ASSOCIATED FRONT
ACROSS THE EASTERN GULF AND SOUTHEAST ALASKA THROUGH FRIDAY. THE
NAM HAS A BETTER INITIALIZATION AND THE AFTERNOON SHORT TERM
FORECAST PACKAGE WILL LEAN OVER THE NAM SOLUTIONS WITH A FEW
COSMETIC TOUCHES TO THE INHERITED GRIDS.

 THE INCOMING FRONTAL BOUNDARY WITH MARITIME AIR MASS WILL RIDE
OVER THE EXISTING COLD AIR ACROSS THE PANHANDLE. THIS ISENTROPIC
LIFTING...OR OVERRUNNING...WILL BEGIN WEST OF YAKUTAT EARLY THIS
EVENING...THEN SPREAD SOUTHEASTWARD THROUGH THE BOXING DAY. WILL
KEEP THE HEAVY SNOW SCENARIO FOR MOST ZONES AS INHERITED. THE LOW
IN THE NORTHERN GULF SEEMS LIKE TO STALL OVER THE NORTH CENTRAL
GULF FOR A WHILE BUT THE ASSOCIATED FRONT HAS RATHER FAST
FORWARDING SPEED. ALONG THE FRONT...A TRIPLE POINT WILL MOVE EAST
ACROSS THE EASTERN GULF LATE TONIGHT THEN THE PANHANDLE ON
FRIDAY. THIS SYNOPTIC CONDITION WILL ENHANCE THE LOW TO MID LEVEL
WIND FIELDS WITH NEAR ADVISORY LEVEL GUSTS ALONG THE COASTAL
SECTIONS. TO SIMPLIFY THE HAZARD GRIDS...HOWEVER...WILL INCLUDE
WIND INFORMATION TO THE WINTER WEATHER PRODUCTS WITH REDUCED
VISIBILITY IN BLOWING SNOW.

 LIGHT SNOW HAS BEGUN IN YAKUTAT AREA AROUND 12 NOON. CONDITIONS
WILL RAPIDLY CHANGE BY EARLY THIS EVENING WITH THE FAST MOVING
FRONT ENTERING THE YAKUTAT ZONE WITH INCREASING SNOW. AS THE
FRONTAL BOUNDARY MOVES FARTHER EAST...PRESSURE GRADIENT BECOMES
TIGHTER AND WEST TO EAST ORIENTED INNER CHANNELS WILL EXPERIENCE
A RAPID INCREASE OF OFFSHORE FLOW TONIGHT INTO FRIDAY MORNING.
FOR HEAVY SNOW EVENT...THE VARIATION OF SNOWFALL AMOUNTS IS
LARGE. EXPECT 4 TO 7 INCHES TONIGHT FOR YAKUTAT WITH ADDITIONAL
5 TO 9 INCHES ON FRIDAY MORNING. OTHER ZONES WILL RECEIVE 3 TO
6 INCHES TONIGHT AND 4 TO 8 INCHES FRIDAY...EXCEPT SOUTHERN
COASTAL ZONES WHERE 3 TO 6 INCHES ARE EXPECTED THROUGH FRIDAY
BEFORE CHANGING OVER TO RAIN MIX IN THE AFTERNOON. THE NAM AND
GFS HINT A WARM AIR ADVECTION BEGINS LATE THIS EVENING FROM THE
WEST. TEMPERATURES WILL STEADILY RISING OVERNIGHT ACROSS THE
LOCAL REGION.

 &&

.LONG TERM...LONG WAVE TROUGH REMAINS OVER THE CENTRAL GULF
THROUGH LATE NEXT WEEK WHILE THE WINTER STORM LOW WILL WEAKEN AND
SLOWLY DRIFT DRIFT SOUTHEAST PARALLELING THE SHORE. THE ASSOCIATED
FRONT WILL HAVE CROSSED MOST OF THE PANHANDLE WITH REMNANTS NEAR
HYDER KEEPING THE WINTER STORM WARNING INTO THE START OF THE LONG
TERM. EXPECTING SNOW SHOWERS TO CONTINUE OVER THE PANHANDLE WITH
RESIDUAL MOISTURE AND ON SHORE FLOW THROUGH THE WEEKEND. BUILDING
HIGH OVER THE YUKON AND SOUTHEASTERLY TRACKING LOW WILL RESULT IN
INCREASED PRESSURE GRADIENT AND OFF SHORE FLOW. RESULTING IN BREEZY
CONDITIONS OVER THE N PANHANDLE, INTERIOR GAPS AND GALE FORCE
WINDS IN THE NORTHERN INSIDE CHANNELS. MARINE WATERS CONTINUE WITH
SMCR ADVISORY LEVELS THROUGH NEXT WEEK AS THE LOW TRACKS SE.

WITH THE STABLE SYNOPTIC PATTERN FORMING MODELS ARE IN GOOD
AGREEMENT THROUGH MOST OF THE LONG TERM. THERE IS A SIGNIFICANT
DIVERGENCE AT THE END WITH THE GFS SHOWING A STRONG LOW
UNDERCUTTING THE LONG WAVE TROUGH AND REACHING THE SOUTHERN
PANHANDLE. USED A 60/30 BLEND OF INHERITED GRIDS AND THE 12Z GFS
OUT TO DAY 4 THEN A 60/30 BLEND OF INHERITED GRIDS WITH HPC
GUIDANCE FOR THE REMAINDER. NO SIGNIFICANT CHANGES RESULTED.

FORECAST CONFIDENCE REMAINS ABOVE AVERAGE THROUGH EARLY NEXT WEEK
THEN DROPS AS MODELS BEGIN THE DIVERGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 3 PM AKST
     FRIDAY FOR AKZ018>021-024>026.
         WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM AKST

     FRIDAY FOR AKZ023-027-028.
         WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM AKST
     FRIDAY FOR AKZ022.
         WINTER STORM WARNING FROM 3 AM TO 9 PM AKST FRIDAY FOR
     AKZ029.
         WINTER STORM WARNING FROM 7 PM THIS EVENING TO 9 AM AKST
     FRIDAY FOR AKZ017.
MARINE...GALE WARNING FOR PKZ022-033-035-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031-032-034.

&&

SJA/PRB