MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1240 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 AND GFS ...SHORTWAVE TROUGH/SURFACE LOW IMPACTING THE MID MS/OH VALLEYS/MID-ATLANTIC/NORTHEAST... PREFERENCE: 00Z ECMWF/00Z 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 00Z GEM THE WEAKEST. THE 12Z NAM/00Z UKMET AND 00Z 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: 00Z ECMWF 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 00Z GEM/00Z UKMET SOLNS ARE A BIT WEAKER. THE 00Z ECMWF TENDS TO SPLIT THE DIFF WITH THE DEPTH AND ACTUALLY OVERALL CLUSTERS RATHER WELL WITH THE LATEST GEFS MEAN AND ECENS MEAN. WILL PREFER THE ECMWF AS A RESULT. ...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: 00Z ECMWF/00Z GEM COMPROMISE CONFIDENCE: ABOVE AVERAGE THROUGH ABOUT 72 HRS...AVERAGE THEREAFTER THE FLOW REALLY BEGINS TO AMPLIFY ACROSS THE SOUTHWESTERN CONUS BY EARLY THIS WEEKEND. THE 12Z NAM AND 12Z GFS ARE AGAIN A BIT QUICKER IN EJECTING THIS SYSTEM INTO THE FOUR CORNERS REGION ON SAT AND THEN THE HIGH PLAINS ON SUN. THE 00Z GEM AND 00Z ECMWF ARE THE SLOWEST WITH THE 00Z UKMET SPLITTING THE DIFF. THE NCEP MODELS HAVE BEEN PERSISTENTLY A LITTLE FASTER THAN THE NON-NCEP SOLNS AS COMPARED TO THE LAST FEW MODEL CYCLES. HOWEVER...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 00Z UKMET LIFTS IT THE FARTHEST TO THE NORTH. THE 00Z GEM AND 00Z ECMWF CLUSTER VERY WELL AND SPLIT THE DIFF. THE 12Z GFS AFTER 72 HRS IS IN BETWEEN THE UKMET AND GEM/ECMWF CAMPS. AT THE SFC...ALL OF THE MODELS SHOW A VERY STRONG SFC LOW DEVELOPING IN THE LEE OF THE CNTRL ROCKIES...AND THERE IS RATHER SOLID AGREEMENT WITH ALL OF THE MODELS WITH THE PLACEMENT OF SFC LOW PRESSURE BY EARLY SUN. HOWEVER...JUST AFTER THIS PERIOD...THE SAME MODEL SPREAD SEEN ALOFT BECOMES NOTABLE AT THE SFC AS WELL. BASED ON MODEL CLUSTERING AND SUPPORT FROM THE LATEST ECENS MEAN...WILL MAINTAIN CONTINUITY AND CONTINUE TO PREFER A SOLN TWD THE ECMWF/GEM CAMP. ...SHORTWAVE TROUGH EDGING INTO THE NORTHWEST SAT AND SUN... PREFERENCE: NON-UKMET CONSENSUS CONFIDENCE: ABOVE AVERAGE ALL OF THE MODELS INDICATE A NEW PACIFIC TROUGH GRADUALLY ADVANCING EAST INTO THE NORTHWEST THIS WEEKEND. ON THE LARGER SCALE THERE IS VERY GOOD AGREEMENT...BUT THE UKMET IS A LITTLE STRONGER THAN THE MULTI-MODEL CONSENSUS WITH THE ENERGY EARLY SAT MOVING INTO WA STATE. THE UKMET ALSO HAS A STRONGER SFC LOW NEAR VANCOUVER ISLAND EARLY SUN COMPARED TO THE REST OF THE GUIDANCE. WILL PREFER A NON-UKMET CONSENSUS. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON