MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 250 PM EDT THU APR 24 2014 VALID APR 24/1200 UTC THRU APR 28/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...SHORTWAVE TROUGH/SURFACE LOW IMPACTING THE MID MS/OH VALLEYS/MID-ATLANTIC/NORTHEAST... PREFERENCE: 12Z ECMWF/12Z UKMET COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE A SHORTWAVE TROUGH AND DEVELOPING SFC LOW OVER THE CNTRL PLAINS THIS MORNING WILL ADVANCE PROGRESSIVELY EASTWARD TODAY THROUGH THE MID MS VLY...AND THEN CROSS THE OH VLY ON FRI. THE MODELS ARE IN GOOD AGREEMENT IN TAKING THIS ENERGY THROUGH THE NRN MID-ATLANTIC AND THE NORTHEAST FRI NIGHT AND EARLY SAT WHILE ALSO SUGGESTING IT WILL WEAKEN AND DAMPEN OUT BY LATE SAT IN FAVOR OF STRONGER UPSTREAM HEIGHT FALLS APPROACHING. THE 12Z GFS OVERALL IS THE STRONGEST SOLN...WITH THE 12Z GEM THE WEAKEST. THE 12Z NAM/12Z UKMET AND 12Z ECMWF SPLIT THE DIFF AND ESSENTIALLY REPRESENT THE MULTI-MODEL CONSENSUS. WILL MAINTAIN CONTINUITY ATTM...AND CONTINUE TO PREFER A ECMWF/UKMET COMPROMISE. ...SHORTWAVE TROUGH/CLOSED LOW ADVANCING FROM THE NORTHERN PLAINS TO THE GREAT LAKES/NORTHEAST... PREFERENCE: 12Z ECMWF/12Z UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW A SHORTWAVE TROUGH CURRENTLY OVER THE NRN PLAINS ADVANCING EASTWARD OVER THE NEXT FEW DAYS AND AMPLIFYING SOMEWHAT AS IT CROSSES THE GRT LAKES REGION. THE ENERGY SHOULD DIG INTO THE NORTHEAST BY SAT AND CAPTURE THE REMNANTS OF THE INITIAL SHORTWAVE CROSSING THROUGH MID MS/OH VLYS TODAY AND FRI. THE 12Z NAM AND 12Z GFS ARE THE STRONGEST SOLNS WITH THE EVOLUTION OF THE CLOSED LOW THAT DEVELOPS. THE 12Z GEM/12Z UKMET AND 12Z ECMWF ARE WEAKER BUT NOT SUBSTANTIALLY WEAKER THAN THE NAM/GFS CAMP. OVERALL...THE STRONGEST MODEL CLUSTERING SUPPORTS A COMPROMISE OF THE ECMWF AND UKMET AND THERE IS SUFFICIENT AGREEMENT FROM THE LATEST GEFS MEAN AND ECENS MEAN THAT THIS WILL BE THE PREFERENCE ATTM. ...DEEP UPPER TROUGH/CLOSED LOW CROSSING THE SOUTHWEST/FOUR CORNERS REGION THIS WEEKEND... ...POWERFUL SURFACE LOW DEVELOPING ACROSS THE MIDDLE OF THE U.S... PREFERENCE: 12Z GFS/12Z ECMWF COMPROMISE CONFIDENCE: ABOVE AVERAGE THROUGH ABOUT 72 HRS...AVERAGE THEREAFTER THE FLOW REALLY BEGINS TO AMPLIFY ACROSS THE SOUTHWESTERN CONUS BY EARLY THIS WEEKEND AS STRONG SHORTWAVE/JET ENERGY DIGS IN OFF THE ERN PAC OCEAN AND ACROSS CA. THE 12Z GEM/12Z UKMET AND 12Z ECMWF HAVE TRENDED JUST A TAD FASTER AND TWD THE ALREADY SLIGHTLY FASTER 12Z NAM/12Z GFS SOLNS IN EJECTING THIS AMPLIFYING TROUGH INTO THE FOUR CORNERS REGION ON SAT AND THEN THE HIGH PLAINS ON SUN BY WHICH TIME THE UPPER TROUGH WILL HAVE GONE NEG-TILT AND CLOSED OFF. OVERALL THERE IS NOT A PARTICULARLY LARGE AMT OF SPREAD ALOFT WITH THE MASS FIELDS AT LEAST UNTIL ABOUT 72 HRS OUT. AFTER ABOUT 72 HRS...THE 12Z NAM PLACES ITS CLOSED LOW SOUTHEAST OF THE GLOBAL MODEL CONSENSUS. THE 12Z UKMET LIFTS IT THE FARTHEST TO THE NORTH. THE 12Z GEM TRENDED FARTHER NORTH...BUT NOT QUITE AS FAR NORTH AS THE UKMET. THE 12Z ECMWF ALSO TRENDED A LITTLE FARTHER NORTH AND CLUSTERS WELL NOW WITH THE 12Z GFS. BOTH THE GFS AND ECMWF ARE IN BETWEEN THE GEM AND NAM SOLNS. GIVEN THE RATHER STRONG MODEL CLUSTERING AND GOOD SUPPORT FROM THE LATEST GEFS MEAN AND ECENS MEAN...WILL PREFER A GFS/ECMWF COMPROMISE. ...SHORTWAVE TROUGH EDGING INTO THE NORTHWEST SAT AND SUN... PREFERENCE: GENERAL MODEL CONSENSUS CONFIDENCE: ABOVE AVERAGE ALL OF THE MODELS INDICATE A NEW PACIFIC TROUGH AND AN ASSOCD COLD FRONT GRADUALLY ADVANCING EAST INTO THE NORTHWEST THIS WEEKEND. ON THE LARGER SCALE THERE IS VERY GOOD AGREEMENT...AND SO WILL PREFER A GENERAL MODEL COMPROMISE TO RESOLVE ANY SMALLER SCALE DIFFS. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON