MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 233 PM EDT MON APR 18 2016 VALID APR 18/1200 UTC THRU APR 22/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/CMC AND ECMWF ...TROUGH/FRONT MOVING INTO THE NORTHEAST LATE MON/TUES WITH SURFACE CYCLOGENESIS OFF NEW ENGLAND TUES... PREFERENCE: NON-GFS CONSENSUS CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT IN DROPPING A SHORTWAVE SOUTHEAST ACROSS THE NORTHEAST BY EARLY TUES AND THIS WILL BE ACCOMPANIED BY A SURFACE COLD FRONT. A WEAK AREA OF LOW PRESSURE WILL CROSS SOUTHERN NEW ENGLAND AND THEN INTENSIFY OFFSHORE BY LATE TUES. THE 12Z GFS GRADUALLY BECOMES A DEEPER OUTLIER COMPARED TO THE OTHER MODELS. THE REMAINING GUIDANCE IS WELL CLUSTERED...AND SO A NON-GFS CONSENSUS WILL BE PREFERRED. ...INTERMOUNTAIN WEST CUTOFF UPPER LOW SHIFTING INTO THE PLAINS WED AND UPPER MIDWEST BY THURS... PREFERENCE: 12Z GFS CONFIDENCE: AVERAGE THE MODELS TAKE THE CURRENT UPPER LOW OVER THE CENTRAL ROCKIES VERY SLOWLY OFF TO THE EAST OVER THE NEXT FEW DAYS WHICH WILL TAKE THE SYSTEM EAST ACROSS THE MIDWEST AND INTO THE GREAT LAKES/OH VALLEY REGION. THE 12Z NAM AND 12Z UKMET ARE A LITTLE FASTER THAN THE MULTI-MODEL CONSENSUS...WITH THE 12Z CMC SLOWER. THE 12Z ECMWF HAS TIMING COMPARABLE TO THE 12Z GFS WITH THE MAIN UPPER LOW WHICH SPLITS THE DIFFERENCE BETWEEN THE SLOWER CMC AND THE FASTER NAM/UKMET...HOWEVER...THE ECMWF HAS A STRONGER AND RATHER SPURIOUS LOOKING SHORTWAVE TROUGH DIGGING DOWN THE WEST SIDE OF THE UPPER LOW BY THURS ACROSS THE CENTRAL PLAINS WHICH IS NOT WELL SUPPORTED BY THE REMAINING MODELS. THE 12Z GFS GENERALLY REFLECTS THE MODEL CONSENSUS THE BEST AND THIS MODEL WILL BE PREFERRED. ...SHORTWAVE MOVING TOWARD THE GREAT LAKES BY THURS... PREFERENCE: NON-CMC CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z CMC IS A TAD SLOW WITH THIS SYSTEM. THE REMAINING MODELS ARE REASONABLY WELL CLUSTERED WITH TIMING AND DEPTH AND SO A NON-CMC CONSENSUS WILL BE PREFERRED. ...UPPER LOW ENTERING CENTRAL WEST COAST WED MORNING... ...SHEARING OUT OVER COASTAL WA/OR BY THROUGH THURS MORNING... PREFERENCE: 12Z UKMET CONFIDENCE: AVERAGE THE 12Z GFS AND 12Z CMC ARE BOTH A BIT DEEPER AND SLOWER THAN THE MODEL CONSENSUS WITH THIS ENERGY. THE 12Z NAM AND 12Z ECMWF ARE NOW THE MOST PROGRESSIVE/WEAKEST SOLUTION...WITH THE 12Z UKMET OVERALL SPLITTING THE DIFFERENCE. WILL LEAN TOWARD THE UKMET FOR NOW AS A COMPROMISE SOLUTION. ...DEEP UPPER TROUGH APPROACHING THE WEST COAST LATE THURS... PREFERENCE: BLEND OF THE 12Z GEFS MEAN AND 00Z ECENS MEAN CONFIDENCE: AVERAGE THE MODELS AGREE IN BRINGING A DEEP LAYER TROUGH TOWARD THE WEST COAST BY LATER THURS. THERE IS RATHER GOOD AGREEMENT WITH THE TIMING OF THE SYSTEM...BUT THERE ARE SOME DIFFERENCES WITH DEPTH. WILL PREFER THE WELL CLUSTERED ENSEMBLE MEANS AS PER THE GEFS MEAN AND ECENS MEAN AT THIS POINT...AS THE 12Z ECMWF AND 12Z CMC APPEAR TO BE DROPPING ENERGY A BIT MORE AGGRESSIVELY DOWN THE WEST SIDE OF THE TROUGH BY LATE THURS. THE 12Z NAM/12Z GFS AND 12Z UKMET ALL HAVE MORE ENERGY STILL LINGERING A LITTLE FARTHER NORTH AND CLOSER TO THE GULF OF AK THROUGH LATE THURS...ALTHOUGH THEY ALL HAVE A FAIRLY DEEP TROUGH APPROACHING THE WEST COAST BY THEN. THIS LATTER CAMP IS SUPPORTED BY THE GEFS MEAN AND ECENS MEAN. WILL STILL FAVOR AN ENSEMBLE MEAN APPROACH AT THIS POINT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON