Gale Warning 368, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1210 PM AST THU DEC 20 2007

.SYNOPSIS...
.SHORT RANGE...
IT SHAKES CONFIDENCE WHEN THE 12Z MODELS HAVE SIGNIFICANT SPREAD
OF SOLUTIONS IN 24 HOUR PROJECTIONS BUT THATS BEEN THE STORY OF
THIS WEEK. IN THIS CASE THE 12Z GFS APPEARS TO BE SUPERIOR TO
ANYTHING ELSE BY INITIALIZATION. USING THE AK-GFS-40 THE LOW
CENTER CONTINUES TO DEVELOP AS PER SATELLITE INDICATIONS AND
TIMING. BY 00Z SAT THIS CENTER ENDS UP AT MIDDLETON ISLAND WHICH
IS REASONABLE. THE 12Z OPERATIONAL GFS ALSO MATCHES SATELLITE
POSITION WELL ON THE SYSTEM MENTIONED ABOVE AT 40N 167W AT 18Z
TODAY. THIS DEVELOPER WILL HAVE IMPLICATIONS FOR THE LONG TERM.

EXPECT HIGH GALES TO DEVELOP TONIGHT ALONG THE COASTAL AND
OUTSIDE WATERS WITH SMALL CRAFT WINDS FOR MUCH OF INNER CHANNELS.
ADVISORY LEVEL WINDS WILL DEVELOP ALONG THE SOUTHERN AND CENTRAL
PANHANDLE COAST...STARTING WITH 27 AND 23 AT MIDNIGHT...THEN 22
AND 28 AT 3 AM.  ADDITIONALLY...COLD AIR IS SLOWLY BEING SCOURED
OUT OF THE AREA AS FLOW HAS TURNED MORE SOUTHWESTERLY.
PRECIPITATION WILL START OUT AS SNOW FOR MOST LOCATIONS AND TURN
TO RAIN FROM SOUTH TO NORTH TONIGHT.  THE EXCEPTION WILL BE IN
THE NORTH WHERE COLDER AIR SINKING IN FROM CANADA WILL KEEP
PRECIPITATION TYPE SNOW.  SNOW ACCUMULATIONS WILL BE SIGNIFICANT
PARTICULARLY IN HAINES ALONG THE CHILKAT VALLEY.  A WINTER STORM
WATCH REMAINS IN EFFECT AND WILL REVIEW THE POTENTIAL FOR A
WARNING OR ADVISORY ACROSS THE NORTHERN INNER CHANNELS.

.LONG RANGE...
PATTERN INDICATES STEADY W-SW FLOW INTO SE AK THRU MIDDLE OF NEXT
WEEK. EMBEDDED IN THE FLOW ARE AT LEAST THREE SEPARATE SHORT
WAVES THAT HAVE DIFFERENT WEATHER AFFECTS WITH THEM. HAVE
COORDINATED WITH ANCHORAGE AND VANCOUVER FCSTRS AND PUBLIC AND
MARINE FORECASTS ARE IN GOOD AGREEMENT ACROSS BORDERS.

FIRST WAVE CONTINUES TO LIFT NORTHWARD OFF THE COAST FRI NIGHT.
THIS WILL HAVE BOTH DECENT PRECIP AMOUNTS AND GALE FORCE WINDS
OVER COASTAL MARINE AREAS...EVEN STORM FORCE IN FAR NORTH ZONE
52. REGARDING PRECIP...CURRENT WINTER STORM WATCH FOR HAINES AREA
FRI WILL LIKELY BE EXPANDED NW FROM THERE FRI NIGHT AND EARLY SAT
ESPECIALLY FOR YAKUTAT ZONE. GFS IS CURRENT MODEL OF CHOICE AND
IT DEPICTS VERY STRONG ISENTROPIC LIFT AND DEFORMATION ALONG WITH
VERY MOIST AIR...POSSIBLY TAPPED INTO TROPICAL PLUME. END RESULT
MAY BE A FOOT OF SNOW IN YAK ZONE OVER 12-18 HR PERIOD FRI NIGHT.
THIS BEARS CLOSE WATCHING.

SECOND SYSTEM IN THE SW FLOW IS CURRENTLY DEVELOPING EAST OF THE
DATELINE AT 160W 38N IS WELL DEFINED BY GFS AND FCST BY MODELS TO
AFFECT SE AK SUN. BECAUSE OF ITS WARM ORIGINS THERE WILL LIKELY
BE A TEMPORARY RAISING OF SNOW LEVEL S AND EAST OF THE LOW
CAUSING FCST ISSUES WITH THE RAIN-SNOW LINE. CURRENT FCSTS LOOK
REASONABLE SHOWING RAIN INSTEAD OF SNOW SUN FROM ABOUT SITKA S
AND EAT TO KETCHIKAN. PETERSBURG-WRANGELL ON THE EDGE BUT WITH
COLD OUTFLOW STILL LIKELY FROM EASTERN BC WILL LEAN TOWARD SNOW
WORDING FROM NORTHERN MISTY FJORDS TO CAPE SPENCER AND POINTS N.
EARLY SUN LOOKS TO OFFER A SHORT BREAK IN PRECIP OVER NORTHERN
ZONES BUT SNOW RETURNS THERE SUN NIGHT AND MON.

YET ANOTHER SYSTEM TUE IS FCST TO TAKE SIMILAR TRACK...THAT IS
LOOPING FROM WEST OF CHARLOTTES TO S PANHANDLE COAST THEN LIFT
NORTHWARD. THIS ONE MAY CUT ACROSS PANHANDLE SOUTH OF JUNEAU
INSTEAD OF CONTINUING UP COAST. IF THAT HAPPENS THE RAIN SNOW
LINE SHOULD BE MORE DEFINITE. WET WESTERLY FLOW IS FORECAST TO
PERSIST WELL INTO NEXT WEEK AND TEMPERATURES ARE PREDICTED TO BE
AT OR BELOW AVERAGE ACROSS SE AK.  TA

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND ADVSRY...ZONES 22-23-27-28 STARTING TONIGHT WINTER
STORM WATCH...ZONE 18 FRIDAY MORNING THRU AFTERNOON
MARINE...GALE...ZONES 22-36-41-42-43-51-52 SMCR...ELSEWHERE