MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 302 PM EDT WED APR 08 2015 VALID APR 08/1200 UTC THRU APR 12/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...UPPER TROUGH CROSSING THE INTERMOUNTAIN WEST/PLAINS AND MIDWEST... ...ACCOMPANYING SURFACE LOW TRACKING INTO THE GREAT LAKES THURS NIGHT... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THE MODELS ARE GRADUALLY COMING INTO BETTER AGREEMENT WITH THE DETAILS OF THE UPPER TROUGH OVER THE INTERMOUNTAIN WEST THAT WILL EJECT OUT INTO THE CENTRAL PLAINS THURS AND THEN LIFT NORTHEAST INTO THE GREAT LAKES REGION ON FRI. LOW PRESSURE ACCOMPANYING THE HEIGHT FALLS WILL DEVELOP OVER THE CO HIGH PLAINS THIS EVENING AND THEN LIFT NORTHEAST ACROSS THE MIDWEST THURS AND ACROSS NORTHERN LOWER MI BY EARLY FRI BEFORE ADVANCING INTO SOUTHEAST ONTARIO. THE 12Z NAM AND 12Z ECMWF ARE NOW BOTH JUST A LITTLE FASTER THAN THE 12Z GFS AND 12Z UKMET SOLUTIONS. THE 12Z GEM FINALLY TRENDED MORE PROGRESSIVE AND FITS IN CLOSE TO THE GLOBAL MODEL CONSENSUS. SOME MODEST SPREAD STILL EXISTS WITH TIMING DEPENDING ON THE FORECAST HOUR...BUT ON THE LARGER SCALE...THERE IS NOW SUFFICIENT AGREEMENT THAT A GENERAL MODEL COMPROMISE WILL BE PREFERRED. ...NORTHERN STREAM SHORTWAVE DROPPING INTO THE UPPER MIDWEST THROUGH FRI... ...ENERGY TRAVERSING THE NORTHEAST ON SAT... PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 60 HOURS BLEND OF THE 12Z GFS AND 12Z ECMWF...AFTER 60 HOURS CONFIDENCE: AVERAGE A NORTHERN STREAM SHORTWAVE WILL DROP DOWN ACROSS THE UPPER MIDWEST AND THROUGH THE GREAT LAKES REGION IN BEHIND THE AFOREMENTIONED SHORTWAVE TROUGH AND ATTENDANT SURFACE LOW THAT LIFTS NORTHEAST THROUGH THE GREAT LAKES REGION. THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM THROUGH ABOUT 60 HOURS...BUT THE 12Z NAM BECOMES A BIT OF A DEEPER OUTLIER THEREAFTER AS THE ENERGY CROSSES THROUGH THE LOWER GREAT LAKES REGION AND THE NORTHEAST. THE 12Z GEM BECOMES A BIT SLOWER THAN THE THE MULTI-MODEL CONSENSUS AFTER 60 HOURS AS WELL...WITH THE 12Z UKMET TENDING TO BE MOST PROGRESSIVE. THE 12Z GFS AND 12Z ECMWF OFFER THE BEST MODEL CLUSTERING AFTER 60 HOURS...BUT A GENERAL MODEL COMPROMISE WILL BE PREFERRED PRIOR TO THIS TIME FRAME. ...SHORTWAVE MOVING INTO THE NORTHWEST FRI AND SAT... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW RELATIVELY MINOR DIFFERENCES WITH A BROAD TROUGH MOVING INTO THE NORTHWEST FRI AND SAT...SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED AT THIS TIME. ...LEAD SHORTWAVE IMPULSE REACHING THE UPPER MIDWEST BY SAT... PREFERENCE: NON-UKMET CONSENSUS CONFIDENCE: ABOVE AVERAGE THE MODELS DRIVE A SHORTWAVE OVER THE PACIFIC NORTHWEST ON THURS GRADUALLY EASTWARD ACROSS THE NORTHERN PLAINS AND INTO THE UPPER MIDWEST BY SAT. THIS WILL BE IN RESPONSE TO THE UPSTREAM SHORTWAVE ADVANCING INTO THE NORTHWEST THROUGH THE PERIOD. THE 12Z UKMET IS NOW THE QUICKEST TO DAMPEN THIS ENERGY OUT VERSUS THE CONSENSUS OF THE 12Z NAM/12Z GFS/12Z GEM AND 12Z ECMWF WHICH NOW AGREE IN HANGING ONTO AT LEAST SOME IDENTIFIABLE WAVE THROUGH THE PERIOD AS IT MOVES INTO THE UPPER MIDWEST. A NON-UKMET CONSENSUS WILL BE PREFERRED. ...SOUTHERN STREAM TROUGH APPROACHING THE BAJA PENINSULA ON SAT... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: AVERAGE THE MODELS DEVELOP AN UPPER LOW NEAR 35N 134W BY 00Z/FRI AND THEN DRIVE THIS ENERGY SOUTHEAST TOWARD THE BAJA PENINSULA ON SAT. THERE IS BETTER MASS FIELD AGREEMENT OVERALL WITH THE 12Z MODELS...BUT THE NAM IS LIKELY A BIT TOO SLOW CONSIDERING THE REMAINING GLOBAL MODELS AND THE ENSEMBLE MEANS. SO WILL PREFER A NON-NAM CONSENSUS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON