Gale Warning 376, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST SUN DEC 23 2007

.SYNOPSIS...
.SHORT RANGE...
MAJOR STORM CENTERED AT 55.5N 137.4W...OR 140 NM SW OF CAPE
DECISION...AT 18Z HAS REACHED MAX INTENSITY AT 966 MB. PUBLIC
HIGH WIND WARNINGS FOR ZONES 28-28 VERIFIED AS DID MARINE STORM
WARNINGS FOR CLARENCE STR AND COASTAL WATERS SOUTH OF CAPE
EDGECUMBE. SATELLITE DERIVED WIND SPEEDS REVEALING SFC WINDS TO
55KT IN BETWEEN BUOYS AND SHIP OBS. SEAS ARE ON THE RISE NOW AND
AT 17Z WERE 27 FT AT CAPE EDGECUMBE BUOY 46084. FARTHER N...PCPN
SHIELD EXTENDS UP TO ABOUT ICY STRAIT BUT DOWNSLOPING EASTERLIES
DRYING OUT LOWER LEVELS. HIGH TIDE IN SE AK OCCURRING BETWEEN NOW
AND NOON AT 15-20 FT..ABOUT A FOOT ABOVE PREDICTED VALUES. WATER
LEVELS WILL DROP QUICKLY THIS AFTERNOON TO MINUS TIDE THIS EVE.

NAM AND GFS BOTH WEAKEN THE LOW STARTING THIS AFTN AND TAKE IT
EAST ACROSS FREDERICK SOUND TONIGHT...GFS A BIT FASTER OF THE
TWO. THERE IS A SWATH OF GALE FORCE WESTERLIES ON BACK SIDE OF
THE LOW. HIGH WIND WARNINGS WILL BE CHANGED TO WIND ADVISORIES
FOR THIS REASON THRU 12 MID FOR ZONE 27 AND THRU 6 PM FOR ZONE
28. OTHER WIND ADV IN ADJACENT ZONES VALID TO 6 PM ALSO AND WILL
STAY WITH THAT PLAN FOR NOW WITH IDEA THAT STRONG WESTERLIES WILL
BE FAIRLY NARROW BAND. WITH FLOW CHANGING TO WESTERLY PRECIP WILL
CONTINUE OVER SOUTHERN ZONES THROUGH MON...GRADUALLY BECOMING
MORE SHOWERY DUE TO COOLING ALOFT. NORTH OF THE LOW TRACK THERE
WILL BE SOME LIGHT PCPN AND LOCALLY MODERATE EAST WINDS THRU THE
EVENING UNTIL LOW EXITS INTO BC. PAYA SHOULD STAY DRY UNTIL LATE
TONIGHT AND EARLY MON WHERN THE DEFORMATION ZONE ON FAR WEST EDGE
OF CLOUD SHIELD PASSES OVER PANHANDLE. TA

.LONG RANGE...THE LONGWAVE PATTERN CONTINUES TO BE ACTIVE IN THE
NORTHEAST PACIFIC THROUGH THE WEEK AS A COLD UPPER LOW PERSISTS
OVER THE BERING SEA EJECTING STRONG TROUGHS EASTWARD ACROSS THE
GULF OF ALASKA. THE NEXT TROUGH REACHES THE EASTERN GULF EARLY
TUE FOLLOWED BY ANOTHER ON THU. THE ENSEMBLE SPREAD IS FAIRLY LOW
WITH THE FIRST SYSTEM BUT STARTS TO GROW SIGNIFICANTLY WITH THE
SECOND. THIS IS EXAGGERATED FURTHER NEXT WEEKEND WHEN MODELS
START TO MIGRATE THE COLD UPPER LOW EASTWARD. WHILE THE TREND FOR
COLDER UNSTABLE AIR IN THE GULF NEXT WEEKEND LOOKS REASONABLE
THERE IS CONSIDERABLE UNCERTAINTY IN THE STRENGTH AND TIMING OF
INDIVIDUAL FEATURES.

BY EARLY TUE THE MAIN SURFACE LOW ASSOCIATED WITH THE UPPER
TROUGH MOVES TO THE NORTH CENTRAL GULF WITH A STRONG FRONT
EXTENDING EASTWARD TO THE SE AK COASTAL WATERS. GFS AND ECMWF
MODEL INDICATE WAVE DEVELOPMENT ON THE FRONT THAT SHOULD ENHANCE
THE SURFACE WIND AS IT NEARS THE COAST. PRECIPITATION WILL BE
MAINLY RAIN EXCEPT IN THE EXTREME NORTHERN INNER CHANNELS.

COLD UNSTABLE AIR BEHIND THE TROUGH WILL HELP TO SET OFF SHOWERS
IN THE GULF AND COOL DOWN THE NORTHERN PANHANDLE/NE GULF COAST BY
MID WEEK. THEN WARM ADVECTION FROM THE NEXT SYSTEM PICKS UP OVER
THE EASTERN GULF ALREADY WED NIGHT. WITH THIS SYSTEM THE JET DIGS
FURTHER SOUTH CAUSING THE FRONT TO BULGE SOUTHEASTWARD AS WELL.
COOLER AIR AND NORTHEAST WINDS PRECEDING THE FRONT WILL LIKELY
PRODUCE MORE SNOW THAN THE PREVIOUS SYSTEM.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND ADVISORIES ZONES 22-23-26>29
MARINE...STORM WRNGS ZONES 36-41-42 GALES ZONES 43-51-52 SCA
ELSW.