EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
203 PM EDT TUE MAR 17 2009
 
VALID 12Z FRI MAR 20 2009 - 12Z TUE MAR 24 2009
 
THE MODELS AND ENSEMBLES OVERALL SHOW SIGNIFICANT MID-UPPER LEVEL
FLOW AMPLIFICATION FOR NOAM OVER THE NEXT WEEK AS POTENT PACIFIC
ENERGY DIGGING SEWD INTO THE WRN US LEADS TO DOWNSTREAM RIDGING
OVER THE EAST-CENTRAL US AND LINGERING TROFFING OVER THE NERN
US/CANADIAN MARITIMES.  HOWEVER...GUIDANCE SPREAD AND UNCERTAINTY
IS MUCH HIGHER WITH THE STRENGTH AND PROGRESSION OF EMBEDDED
SYSTEMS...ESPECIALLY BY SUN-TUE. 

GUIDANCE DIFFERENCES INCREASE IN THIS FLOW SUN-TUE AND THE
00/06/12 UTC GFS RUNS OFFER SOLUTIONS NEAR THE FASTER EDGE OF THE
FULL ENVELOPE OF SOLUTIONS WHILE RECENT ECMWF AND UKMET/CANADIAN
ARE GENERALLY WITHIN THE MORE AMPLIFIED AND LEAST PROGRESSIVE
CLUSTER OF SOLUTIONS.  00 UTC ECMWF AND CANADIAN ENSEMBLES ARE
MORE AMPLIFIED AND LESS PROGRESSIVE THAN GFS ENSEMBLES...BUT
ALMOST ALL ENSEMBLES SIT SOMEWHERE IN BETWEEN THE MORE
CONTRARY/VARIED DETERMINISTIC GLOBAL MODELS.  THERE ARE SOME
CLIMATOLOGICAL REASONS TO FAVOR AMPLIFICATION.  HOWEVER...EMBEDDED
SYSTEM WAVELENGTH SPACING OUT FROM THE ERN PACIFIC IS RELATIVELY
SMALL HEADING INTO NEXT WEEK AND THE ECMWF HAS EXHIBITED A BIAS
TOWARD OVER-AMPLIFICATION AT LONGER TIME FRAMES RECENTLY. 
ACCORDINGLY...PREFER TO MAINTAIN HPC CONTINUITY WITH OUR FINAL
GUIDANCE PACKAGE AND STAY WITH PREFERERENCE FOR A COMPROMISE 70%
ECMWF ENSEMBLE MEAN AND 30% GFS ENSEMBLE MEAN BLENDED SOLUTION
THAT LEANS TOWARD REASONABLY DEEP FLOW AMPLIFICATION AND FAIRLY
SLOW SYSTEM PROGRESSIONS.   

SCHICHTEL