MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 227 PM EDT SAT APR 23 2016 VALID APR 23/1200 UTC THRU APR 27/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SYSTEM MOVING THROUGH NORTHERN PLAINS/GREAT LAKES/NEW ENGLAND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE WHAT APPEAR TO BE MINIMAL DIFFERENCES ALOFT TRANSLATE INTO MODEST SURFACE DIFFERENCES WITH THE FRONTAL ZONE ACROSS THE NORTHERN MID-ATLANTIC STATES TUESDAY MORNING. FOR DAY 2 (SUNDAY 00Z-MONDAY 00Z), THERE HAS BEEN A SUBTLE NORTHWARD TREND IN SOME OF THE DETERMINISTIC AND ENSEMBLE GUIDANCE NEAR THE IL/WI BORDER. FOR DAY 3 (MONDAY 00Z-TUESDAY 00Z), THERE HAS SIMPLY BEEN A TIGHTENING OF THE GLOBAL ENSEMBLE LOW SPREAD, WHICH NOW INCLUDES A THIRD SURFACE WAVE IN THE GULF OF ME. BY TUESDAY MORNING, THE 12Z UKMET LEAVES THE SAFE CONFINES OF THE BEST 00Z GLOBAL ENSEMBLE CLUSTERING, STRAYING TOO FAR NORTH ACROSS NY. TO DEAL WITH THE MODERATE FRONTAL ZONE DIFFERENCE, A COMPROMISE OF THE 12Z NAM/12Z GFS/12Z CANADIAN/12Z ECMWF LOOKS GOOD, WHICH IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. DEEP CYCLONE EMERGING INTO THE HIGH PLAINS LATE TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE DETERMINISTIC GUIDANCE LIES WELL WITHIN THE 00Z GLOBAL ENSEMBLE CLUSTERING AS THE COLORADO LOW DEVELOPS IN THE HIGH PLAINS. TO DEAL WITH LINGERING DETAIL ISSUES SUCH AS SLIGHT DEPTH ISSUES ALOFT AND SLIGHT PROGRESSION ISSUES, A GENERAL MODEL COMPROMISE SHOULD DO WELL, WHICH IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. SYSTEM APPROACHING THE PACIFIC NORTHWEST TUESDAY AFTERNOON TROUGH MOVING THROUGH THE SOUTHERN PLAINS EARLY SUN MORNING UPPER TROUGH MOVING THROUGH THE EASTERN U.S. TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE MODELS HANDLE THESE SYSTEMS SIMILARLY. TO DEAL WITH ANY LINGERING DETAIL ISSUES, A GENERAL MODEL COMPROMISE IS ADVISED WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH