MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1232 AM EDT WED APR 08 2015 VALID APR 08/0000 UTC THRU APR 11/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SURFACE LOW OVER THE MID MS VALLEY THROUGH EARLY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE ONLY MINOR TIMING DIFFERENCES REMAIN WITH THIS LOW BEFORE DISSIPATING LATER TODAY. A GENERAL MODEL COMPROMISE IS PREFERRED TO SMOOTH OUT LINGERING DETAIL DIFFERENCES. WRN UPPER TROUGH AXIS REACHING THE CNTRL PLAINS THU MORNING ACCOMPANYING SURFACE LOW TRACKING INTO THE GREAT LAKES THU NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z NAM/GFS AND 12Z UKMET CONFIDENCE: SLIGHTLY BELOW AVERAGE SOME WEAKER TRENDS HAVE BEEN NOTED IN THE DETERMINISTIC/ENSEMBLE GUIDANCE REGARDING THE SHORTWAVE AS IT REACHES THE CNTRL PLAINS EARLY THU...BUT THE 12Z ECMWF CONTINUES TO BE WEAKEST AND UNSUPPORTED BY THE LATEST 500 MB ENSEMBLE SPAGHETTI HEIGHTS. INTO FRI AND SAT...THE 00Z NAM/GFS ARE TOWARD THE FASTER EDGE OF THE ENSEMBLE SPREAD...WITH THE 12Z UKMET TOWARD THE MIDDLE TO SLOWER SIDE OF THE SPREAD. IN TERNS OF INTENSITY...THE NAM/GFS/UKMET ARE SIMILAR...BUT A BLEND OF THEIR TIMING DIFFERENCES IS PREFERRED...WITH THOUGHTS THAT THE 12Z CMC IS TOO SLOW AND THE 12Z ECMWF A BIT TOO WEAK. MID LEVEL SHORTWAVE TROUGH DROPPING INTO THE N-CNTRL U.S. FROM CANADA THU-FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z NAM/GFS AND 12Z UKMET CONFIDENCE: SLIGHTLY BELOW AVERAGE THE MODELS CONTINUE TO STRUGGLE WITH THE DEGREE OF SHORTWAVE ENERGY THAT DROPS DOWN INTO THE NORTHERN U.S. THU NIGHT AND FRI BUT BETTER RUN TO RUN CONTINUITY EXISTS TONIGHT COMPARED TO MON NIGHT. THE 12Z ECMWF REMAINS UNSUPPORTED EXCEPT FOR THE 12Z ECMWF MEAN TO SOME DEGREE...WHICH SHOWS MORE AMPLIFICATION THAN THE 12Z ECMWF. THE 12Z CMC IS TOWARD THE AMPLIFIED/WESTERN EXTREME OF THE LATEST MODEL SPREAD WITH THE 00Z NAM/GFS AND 12Z UKMET MAKING UP AN AGREEABLE COMPROMISE IN THE MIDDLE...CLOSEST TO THE LATEST SREF/GEFS/EC ENSEMBLE MEANS. CONFIDENCE REMAINS LIMITED WITH THIS FEATURE DUE TO THE POTENTIAL FOR PHASING/INTERACTION WITH THE ENERGY JUST TO ITS SOUTH. SURFACE WAVE EXITING OFF THE MID-ATLANTIC COAST TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z NAM...00Z GFS AND 12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z UKMET AND 12Z CMC ARE A BIT FARTHER NORTH WITH THE SURFACE LOW PLACEMENT...AWAY FROM THE REMAINING DETERMINISTIC AND ENSEMBLE MEAN CONSENSUS. THE NAM/GFS/ECMWF SHOW GOOD AGREEMENT AND A BLEND OF THESE THREE MODELS FORMS A GOOD COMPROMISE. SHORTWAVE TROUGH APPROACHING THE NORTHWEST ON FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW RELATIVELY MINOR DIFFERENCES WITH A TROUGH APPROACHING THE PACIFIC NORTHWEST BY FRI SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO