708
FXUS02 KWBC 291900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
259 PM EDT THU OCT 29 2009
VALID 12Z SUN NOV 01 2009 - 12Z THU NOV 05 2009
WE HAVE HIGH CONFIDENCE IN A PROGRESSIVE AND DEAMPLIFYING LONGWAVE
PATTERN ACROSS THE LOWER 48 STATES THRU TUE DAY 5. BY TUE DAY
5...MODEL CONSENSUS SHOWS ABOVE NORMAL HEIGHTS OVER THE WRN STATES
AND A BROAD TROF ALONG 80W. BEYOND DAY 5...ENSEMBLE SPREAD IN THE
ERN PACIFIC FROM THE GULF OF ALASKA SEWD TO OFF THE NRN CA COAST
BECOMES QUITE LARGE ESPECIALLY IN THE 00Z/29 ECMWF RUN. THE HIGH
UNCERTAINTY CONCERNS THE POSSIBLE SPLITTING OF A PACIFIC TROF MOST
MODELS SHOW NEAR 150W TUE DAY 5...AS ITS INTERACTS WITH CYCLONIC
FAST FLOW PUNCHING EWD ALONG 50N S OF THE ALEUTIANS. NOT
SURPRISINGLY...OUR CONFIDENCE LEVEL DROPS STEADILY BEYOND DAY 5
DOWNSTREAM OVER THE LOWER 48 STATES.
WHILE THE FORECAST PATTERN OF A DECENT APPALACHIAN/ E COAST TROF
BY THE DETERMINISTIC ECMWF MAY STILL HAVE SOME MERIT DAY 5 AND
BEYOND...A CONSENSUS OF THE 00Z/29 ENSEMBLE MEANS OF THE
ECMWF/GEFS/NAEFS IS LESS AMPLIFIED THAN THE DETERMINISTIC 00ZAND
12Z/29 ECMWF WITH THAT TROF. WE PREFER TO STAY FLATTER THAN THE
ECMWF WITH THE ERN CONUS TROF THE MIDDLE OF NEXT WEEK GIVEN THE
FAIRLY HIGH ENSEMBLE SPREAD OFF THE NRN CA/PACIFIC NW/BC/SRN
ALASKAN COASTS THAT WILL BE GRADUALLY WORKING ITS WAY EWD INTO THE
NW QUADRANT OF THE NATION AT THAT TIME.
DOWNSTREAM OVER THE CONUS...ANOTHER SPLITTING TROF HAUNTS
FORECASTERS HALLOWEEN AND THE DAY AFTER. THE SPLITTING SRN PORTION
OF THE TROF THAT WILL BE EXITING THE FOOTHILLS OF THE ROCKIES IN
THE SHORT RANGE STILL PRESENTS A BIG CHALLENGE FOR MODELS. THERE
IS QUITE A DIFFERENCE FOR SUN DAY 3 IN THE HANDLING OF THIS SYS
BETWEEN THE NAM/GFS/UKMET/CANADIAN/ECMWF. A SLIGHTLY WEAKER/SWD
DISPLACED VERSION OF THE NEW 12Z HIRES UKMET IS OUR PREFERRED
SOLUTION SUN DAY 3 ALONG THE MID ATLANTIC COAST. THIS PRESERVES
OUR UPDATED PRELIM CONTINUITY WHICH WAS LARGELY BASED ON THE
06Z/29 GFS. THE 06Z/29 GFS AND ENSEMBLE SPAGHETTI PLOTS HAD
FAVORED A SOMEWHAT STRONGER SFC WAVE FARTHER N ALONG THE E COAST
THAN DEPICTED BY THE EARLY PRELIM CONTINUITY.
SENSIBLE WEATHER WILL BE QUIET ONCE THE DAY 3 SUN WAVY COLD FRONT
CLEARS THE E COAST OF THE CONUS. A WEATHER PATTERN FEATURING
MOSTLY SEASONABLE TEMPS AND LITTLE OR NO PRECIP WILL CONTINUE
ACROSS MOST OF THE NATION UNTIL THE NEXT ROUND OF PACIFIC ENERGY
DECIDES WHAT IT WANTS TO DO BEYOND DAY 6. THERE IS QUITE A RANGE
IN THE LATITUDE OF SOLUTIONS FROM 12Z/29 DETERMINISTIC MODELS
VCNTY OF 150W FOR WED DAY 6 CONCERNING THE DEVELOPMENT OF ANOTHER
PACIFIC CLOSED UPPER LOW. I WOULD NOT PUT MUCH STOCK IN ANY OF
THESE SOLUTIONS AND JUST SHOW SOME PERIODS OF MOSTLY LIGHT PCPN
AFFECTING THE COASTAL AND CANSCADE RANGES AND FAR NRN ROCKIES
UNTIL A MORE ORGANIZED BATCH OF ENERGY CAN REACH THE W COAST OF
THE CONUS.
FLOOD
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