Storm Warning 48, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
552 AM AKST MON NOV 10 2008

.SHORT TERM...A COMPLICATED WEATHER PATTERN THROUGH TONIGHT. A
WEAKENING FRONT CURRENTLY OVER THE PANHANDLE WILL CONTINUE TO
SHEAR APART THIS MORNING AT MID LEVELS...HOWEVER AS THE UPPER
TROUGH MOVES NORTHEASTWARD THIS WILL ENHANCE THE OVERRUNNING
PRECIP ALONG THE 295 K ISENTROPE, SO EXPECT RAIN TO DEVELOP
ACROSS THE SOUTHERN PANHANDLE WITH A RAIN/SNOW MIX NORTH OF
FREDERICK SOUND. WHILE 850 MB TEMPS ARE NOT AS COLD AS WOULD
NORMALLY BE SEEN WITH SNOW, THE COLD AIR IN PLACE AT THE SURFACE
AND THE CONTINUED STRONG EAST TO NORTHEAST SURFACE PRESSURE
GRADIENT WILL ALLOW FOR A CONTINUED SUPPLY OF COLD AIR. BUT ALSO
THIS EAST TO NORTHEAST SURFACE PRESSURE GRADIENT WILL BRING DRIER
LOW LEVEL AIR INTO THE PANHANDLE SO EXPECT PRECIP AMOUNTS TO BE
LIGHT THROUGH THIS AFTERNOON. AS FAR AS WINDS...THE EAST-WEST
ORIENTED CHANNELS WILL CONTINUE TO BLOW SMCR THROUGH TODAY WHILE
THE MID LEVEL FRONT SHEARS APART. AND NOW FOR THE COMPLICATED
PART...A DEVELOPING 975 MB LOW IN THE NORTH PACIFIC WILL ADVECT
NORTHEASTWARD INTO THE SOUTHERN GULF TONIGHT. UPPER LEVEL CLOUD
TRACK WINDS ARE QUITE STRONG WITH THIS SYSTEM, ABOVE 200 KNOTS
SOUTH OF THE ALEUTIANS AT 300 MB CURRENTLY. NONE OF THE MODELS
HAVE UPPER LEVEL WINDS THIS STRONG. ALSO THERE IS SUFFICIENT MID
LEVEL CAA BEHIND THE SYSTEM FOR THE LOW TO DEVELOP A STRONGER MID
LEVEL WARM CORE. THIS WOULD ALLOW FOR A MORE SOUTHERN TRACK AS
THE 00Z AND 06Z NAM SHOWS. PREFERRED A SLIGHTLY WEAKER 00Z
UKMET/GFS BLEND THIS MORNING WHICH WILL STILL BRINGING GALE FORCE
WINDS TO THE EASTERN GULF AND WIND ADVY GUSTS TO THE SOUTHERN
PANHANDLE TONIGHT.

 FOR TONIGHT THE GALE FORCE LOW WILL CONTINUE TO STRENGTHEN AS IT
ADVECTS NORTHEASTWARD INTO THE EASTERN GULF AS THE MID LEVEL
TROUGH TILTS MORE NEGATIVE. GALE FORCE WINDS WILL PICK UP ALONG
THE OUTER COAST AND WIND ADVY GUSTS WILL BEGIN BY THIS EVENING
ALONG THE SOUTHERN PANHANDLE. ALSO WITH THE STRONG LOW
APPROACHING THE SURFACE PRESSURE GRADIENT OUT OF THE EAST WILL
INCREASE SUBSTANTIALLY...THEREFORE EXPECT GUSTS TO 40 KNOTS OUT
OF INTERIOR PASSES. THE 00Z AND 06Z NAM ADVERTISES AN INVERSION
JUST ABOVE MOUNTAIN TOP IN THE DOWNTOWN JUNEAU AREA TONIGHT AND
WITH THE STRONG CROSS BARRIER FLOW COULD SEE TAKU WINDS DEVELOP
IN DOWNTOWN JUNEAU AND DOUGLAS. HOWEVER THE INVERSION AT
4000 FEET DOES NOT LOOK VERY STABLE AT THIS POINT LATE TONIGHT SO
ONLY EXPECT GUSTS TO 35 MPH LATE. ALSO WITH STRONG NORTHERLY
PRESSURE GRADIENT IN LYNN CANAL TONIGHT COULD SEE WIND ADVY GUSTS
NEAR SKAGWAY LATE. AS THE LOW APPROACHES AND THE PVA AT MID
LEVELS MOVES OVER THE PANHANDLE EXPECTING RAIN TO INCREASE FROM
SOUTH TO NORTH. NORTH OF ICY STRAIT EXPECT MAINLY SNOW AS THE
COLD AIR WILL REMAIN IN PLACE WITH THE STRONG NORTHEASTERLY WINDS
WITH SNOW ACCUMULATIONS OF 1 TO 2 INCHES TONIGHT. THE BEST
OVERRUNNING SCENARIO DOES NOT OCCUR UNTIL AFTER MIDNIGHT TONIGHT
WITH STRONG OMEGA IN THE DENDRITIC GROWTH ZONE FOR JUNEAU AND
POINTS NORTHWARD. IF THE SLOWER STRONGER 06Z NAM SCENARIO
VERIFIES COULD SEE A HEAVIER BAND OF SNOW LATE MONDAY/EARLY
TUESDAY AS A DEFORMATION BAND FORMS NORTH OF THE 850 MB MAX
VORTICITY BAND NORTH OF ICY STRAIT. ALL IN ALL A COMPLICATED
WINDY WEATHER PATTERN THROUGH TONIGHT.

.LONG TERM...A HIGHLY AMPLIFIED AND PROGRESSIVE LONG WAVE PATTERN
CONTINUES OVER THE NORTH PACIFIC...BERING SEA...AND GULF OF ALASKA
THROUGH THE LONG RANGE FORECAST FORECAST PERIOD. THIS CONTINUES TO
RESULT IN GENERALLY GOOD AGREEMENT AMONGST THE MODELS IN THE UPPER
LEVELS. BUT SMALL VARIATIONS IN THE AMPLIFIED UPPER LEVEL PATTERN
ARE GENERATING LARGE DIFFERENCES IN THE SURFACE PATTERNS BEING
DEPICTED IN THE MODELS. AND SO...THE GENERAL FEATURES AT THE
SURFACE ARE ALL BEING REPRESENTED BY THE MODELS BUT THE DETAILS ON
TIMING...TRACK...AND INTENSITY ARE INHERENTLY UNCERTAIN. WEIGHTED
UKMET HEAVILY EARLY ON IN THE LONG RANGE PERIOD BUT THEN FAVORED
ECMWF THROUGH SATURDAY. FINISHED THE LONG RANGE GRIDS WITH GFS BUT
SIGNIFICANTLY WEAKENED THE LOW BEING DEPICTED IN THE NORTH CENTRAL
GULF. DO NOT NORMALLY PUT A LOT OF STOCK IN 06Z MODEL RUNS...BUT
THE 10/06Z GFS LOOKS A LOT MORE LIKE THE ECMWF WHICH TEND TO
SUPPORT THE DECISION TO WEAKEN THIS LOW IN GRIDS.

LONG RANGE FORECAST BEGINS WITH A TRIPLE POINT FEATURE LOCATED
WEST OF CAPE DECISION AND A WEAKENING FRONTAL BAND OVER THE
NORTHERN OUTER COAST GENERATING STRONG EASTERLY GALES OVER THE
NORTHEAST GULF. WINDS RELAX TUESDAY NIGHT AND THEN A LOW THAT
PREVIOUSLY FORMED ALONG THE FRONTAL BOUNDARY CLIPS THE SOUTHERN
PANHANDLE AS IT HEADS INTO BRITISH COLUMBIA. NOT A LOT HAPPENS
WIND WISE AFTER THAT WITH LOW LEVEL ONSHORE FLOW THROUGH THURSDAY
MORNING. A SURFACE RIDGE BRIEFLY BUILDS IN ON THURSDAY AFTERNOON
BUT THEN GETS DISPLACED TO THE EAST BY ANOTHER STRONG LOW.
INITIALLY GENERATED STORM FORCE WINDS OVER THE GULF ASSOCIATED
WITH THIS LOW...BUT DID NOT FEEL CONFIDENT ENOUGH WITH THIS
SCENARIO SO LIMITED WINDS TO GALES. THE LOW IS FORECAST TO
EVENTUALLY COME ASHORE NEAR ICY BAY SATURDAY AFTERNOON...FILLING
AS IT DOES. EVEN SO...HIGH PRESSURE BUILDING IN FROM THE SOUTH
WILL MAINTAIN A STRONG PRESSURE GRADIENT AND KEEP GALES IN THE COASTAL
MARINE FORECAST FROM THURSDAY NIGHT INTO SUNDAY NIGHT.

LOTS OF POP IN THE LONG RANGE FORECAST WITH A BRIEF BREAK THAT
ARRIVES ALONG THE SOUTHERN OUTER COAST THURSDAY MORNING AND MOVES
NORTH THROUGH THURSDAY NIGHT. BY FRIDAY MORNING...BACK TO A HIGH
POP SCENARIO WITH ABUNDANT QPF AS WELL. GENERATED RAIN/SNOW HEAVY
AT TIMES THURSDAY NIGHT THROUGH FRIDAY NIGHT FOR ZONE 17 AS WELL
AS THE SOUTHERN ZONES BUT CONSIDERED THAT MUCH TOO FAR IN THE
FUTURE TO STATE WITH CONFIDENCE IN THE FORECAST...HENCE POST
EDITED IT OUT. ELSEWHERE...COULD SEE UP TO 3 INCHES ACCUMULATION
OF SNOW IN ZONE 20 BETWEEN THE END OF THE SHORT RANGE PERIOD AND
THROUGH VETERANS DAY. POSSIBLY ANOTHER 1 TO 2 INCHES THROUGH
TUESDAY NIGHT. OTHERWISE...NOT A LOT OF SNOW IN THE LONG RANGE FORECAST

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 6 PM THIS EVENING TO 6 AM AKST TUESDAY FOR
         AKZ027.
	 WIND ADVISORY FROM 9 PM THIS EVENING TO 6 AM AKST TUESDAY FOR
 	 AKZ028.
MARINE...GALE WARNING FOR PKZ022-033>036-041>043-051-052.
	 SMALL CRAFT ADVISORY FOR PKZ011>013-021-031-032.

&&

PSS/FRITSCH