Gale Warning 253, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM ADT THU OCT 4 2007

.SYNOPSIS...

.SHORT RANGE...MOSTLY CLOUD FREE ACROSS THE NORTHERN ZONES
OVERNIGHT CAUSED AREAS OF FOG...LOCALLY DENSE FOR SHORT TIME
PERIOD...AND RADIATION COOLING FOR COLD MERCURY READINGS SHORTLY
BEFORE SUNRISE.  FREEZE WARNING AND FROST ADVISORY WERE EXPIRED
AT 9 OCLOCK AS PLANNED.  WITH THE INCOMING LOW...OVERNIGHT LOWS
TONIGHT SHOULD STAY ABOVE 40 DEGREES EXCEPT EXTREME NORTHEAST
ZONE WHERE WINTER STORM WATCH CONTINUES ABOVE 2500 FEET.
COORDINATED WITH VANCOUVER TO KEEP THE SNOW LEVEL AROUND 2500
FEET TONIGHT.

LATEST MODEL OUTPUTS SHOW A GOOD CONSISTENCY FOR TONIGHT AND
FRIDAY.  A WEAK UPPER LOW SOUTHEAST OF THE QUEEN CHARLOTTES IS
DRIFTING SLOWLY TO THE BRITISH COLUMBIA COAST FOLLOWED BY A WEAK
UPPER RIDGE BUILDING OVER THE EASTERN GULF.  THIS RIDGE IS
FORECAST TO MOVE QUICKLY SOUTHEAST LATE TONIGHT AND GIVES A WAY
FOR THE INCOMING TROUGH FROM THE NORTHWEST.  THIS SHORTWAVE
TROUGH WILL CONTINUE TO MOVE SLOWLY EAST THROUGH FRIDAY.  AT THE
LOWER LEVEL...A BUILDING OF WEAK RIDGE OVER SOUTH CENTRAL GULF
HAS NO EFFECT FOR THE SOUTHEAST ALASKA...OR A MINIMUM EFFECT FOR
THE EXTREME SOUTHERN ZONES THROUGH THIS AFTERNOON.  THE RIDGE
WILL QUICKLY DIE EARLY THIS EVENING WELL SOUTHEAST OF THE QUEEN
CHARLOTTES LATE THIS AFTERNOON.

THE MAIN CONCERN SHOULD BE THE WIND FIELD LATE TONIGHT THROUGH
EARLY FRIDAY.  SATELLITE IMAGERY ALREADY SHOWS THE LEADING EDGE
OF OUTFLOW BOUNDARY FROM THE INCOMING FRONT ARRIVING WEST OF
YAKUTAT BAY.  THIS IS A LITTLE FASTER THAN THE MODEL GUIDANCE. AS
FAR AS THE MODEL TENDENCY IS CONSIDERED OVER THE PAST SEVERAL
DAYS...THIS TREND IS NOT A SURPRISE.  THE BOTTOM LINE IS MODEL
CONSENSUS KEEPS A BIT DOWNPLAY IN INTENSITY FOR THE INCOMING LOW
AND ITS ASSOCIATED FRONT FOR TONIGHT AND FRIDAY.  THE INHERITED
FORECAST GRIDS FOR SHORT RANGE DESK LOOK EXCELLENT AND NO NEED TO
MAKE ANY BIG CHANGES. AHN

.LONG RANGE...FRONTAL PASSAGE THROUGH PANHANDLE TO B.C. WILL
STILL LEAVE THE OLD PARENT LOW OF 988 MB IN PWS FRI NIGHT.
COLD AIR ADVECTION WILL BE STRONG AND PERSISTENT EXCEPT FOR THE
SOUTHERN PANHANDLE.  THE TRAILING COLD FRONT ACROSS THE CENTRAL
B.C. FRI NIGHT AND CONT S UNTIL A WV ON THE FRONT TRACKS NE
ACROSS CAPE ST JAMES WITH A CENTRAL PRES OF ABOUT 995 MB.
THRFTR THE COLD FRONT WILL MOVE RAPIDLY S OF OUR FORECAST
DOMAIN AND ALLOW THE COLD AIR ADVECTION TO EXTEND SE WELL
BEYOND THE PANHANDLE AND PERSIST.

SOUTH OF PANHANDLE MON NIGHT...LITTLE CHANGE TO FORECAST
PACKAGE BUT A SYSTEM WILL BE CLOSE BY AND IS BEING MONITORED.
LARGE MODEL DIFFERENCES AS WELL AS SPREADOUT OF GFS ENSEMBLE
SOLUTIONS IS SHOWN.  THESE DIFFERENCES MAY NOT MATTER TO OUR
FORECAST DOMAIN AS THE LOW IS SUPPOSED TO TRACK NE AND
ONSHORE B.C.  HOWEVER...THE WIDE RANGE OF SOLUTIONS INCLUDE
IMPORTANT TRACK DIFFERENCES...THE GFS IS GEN TRACKING THE LOW
MORE ZONALLY AND THEN ONSHORE VACOUVER ISLAND.  THE ECMWF HAS
A SLOWER TRACK FARTHER N...AND THE CURRENT RUN INCLUDES A
SHARP INVERTED TROUGH EXTENDING UP TO DIXON ENTRANCE 00Z WED.
THIS LATER SOLUTION MIGHT ULTIMATELY MEAN A SECOND LOW IN OR
NEAR DIXON ENTRANCE.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WINTER STORM WATCH ABV 2500 FT FOR AKZ018.
         WND ADV FOR ALL XCP AKZ018-029.

MARINE...GALE FOR PKZ043-051-052 AND PKZ310.
         SCA FOR ALL INNER CHANNELS.