EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
156 PM EDT SUN MAR 15 2009
 
VALID 12Z WED MAR 18 2009 - 12Z SUN MAR 22 2009
 
THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7 WERE
CONSTRUCTED USING A PROGRESSIVE BLEND FROM THE 00Z/15 ECMWF TOWARD
THE 00Z/15 GEFS MEAN...WHICH SHARE MORE IN COMMON THAN ANY OTHER
GUIDANCE FROM THAT MODEL CYCLE...INCLUDING THE DETERMINISTIC GFS. 
THE NEW FEATURE THIS FORECAST...NEW TO ALL THE MODELS BUT THE GEM
GLOBAL WHICH SHOWED IT AS EARLY AS ITS 00Z/14 RUN...IS THE SHARPLY
SPLITTING TROUGH ALONG THE WEST COAST MID PERIOD.  THERE HAS NOT
BEEN MUCH IN THE WAY OF A DIRECT SYNOPTIC HIT INTO SOUTHERN
CALIFORNIA FOR SOME TIME NOW...SO AM WARY OF THE MOST AMPLIFIED
SOLUTIONS INCLUDING THE 00Z/15 GEM GLOBAL.  THE HEAVY WEIGHTING OF
THE MORE ZONAL GEFS MEAN DAYS 6 AND 7 SHOULD BE ENOUGH TO ADDRESS
THIS UNCERTAINTY.  THE NATION EAST OF THE ROCKIES LOOKS DRY...WITH
THE EXCEPTION OF THE SOUTHERN PLAINS WHERE ENOUGH RETURN FLOW FROM
THE GULF OF MEXICO DURING THE SECOND HALF OF THE FORECAST SHOULD
INITIATE A SHOWERY PERIOD.

NO CHANGES TO EARLY MORNING PRELIMS. ECMWF ENSEMBLES NOT AVAILABLE
AND 06Z GFS AND ITS ENS MEAN FOLLOW THE 00Z RUN. ALL MODELS AND
AVAILABLE ENS MEANS SHOW INCREASING AMPLITUDE WITH THE PAC TROF
APPROACHING THE WEST COAST DAYS 6 AND 7. RECENT VERIFICATION AND
AN OBJECTIVE LAGGED AVERAGE FORECAST TREND OF THE PRECEDING 4
CYCLE RUNS OF GFS AND ECMWF ALONG WITH A SUBJECTIVE LOOK AT
PRECEDING MODEL RUNS SHOW A MORE PROGRESSIVE AND LESSER AMPLIFIED
NATURE AND TREND OF THE PATTERN OVER CONUS. ECMWF IN PARTICULAR
HAS HAD TROF OVERAMPLICATION PROBLEMS BEYOND DAY 5. THUS THE VERY
AMPLIFIED AND CUTOFF SOLUTIONS OF ECMWF AT DAYS 7 AND 8 ARE VERY
SUSPECT AND ENS MEANS OF THE GFS ARE A MORE LIKELY SOLUTION AT
THIS TIME. WHILE LATE MARCH INTO MAY IS CUTOFF SEASON ECMWF HAS
BEEN OVER AGGRESSIVE FORECASTING THESE SOLUTIONS AND THEY HAVE NOT
BEEN VERIFYING. 

12Z GFS CLOSE TO 00Z AND 06Z RUN UNTIL LATE DAY 6 AND 7 WHERE THE
EPAC/WRN TROF IS MUCH FASTER THAN PRIOR RUNS OR ENSEMBLES NEARLY
WITH ITS AXIS TO THE FOUR CORNERS AREA. LATEST CMC CONTS TO BE AS
AMPLIFIED AS ITS 00Z RUN AND UKMET IS ALOS SIMILAR TO ITS PRIOR
RUN. NO CHANGES FOR AFTN FINALS.   
CISCO/ROSENSTEIN