MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1210 PM EDT THU MAY 15 2014 VALID MAY 15/1200 UTC THRU MAY 19/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ...HIGH AMPLITUDE UPR TROF PUSHING VERY SLOWLY EAST ACRS THE EASTERN U.S... PRELIMINARY PREFERENCE: CONTINUITY CONFIDENCE: AVERAGE MOST OF THE MODEL ISSUES HERE ARE MESOSCALE IN NATURE..WHILE IN GENERAL...THERE IS GENL MODEL AGREEMENT IN THE LARGE SCALE MODEL HANDLING/PROGRESSION OF THE HIGH AMPLITUDE UPR TROF AND ASSOCD N/S FRONTAL SYSTEM PUSHING OFF THE SE COAST DAY 1..AND MORE SLOWLY ACRS NEW ENGLAND DUE TO DOWNSTREAM RETROGRADING UPR RIDGE DAYS 2 AND 3. CONTINUITY IS BEST CHOICE HERE IN LIEU OF VERY SLOW MOVEMENT OF SYSTEM AND LITTLE IN THE WAY OF SIGNIFICANT MODEL TRENDS. NAM AND OTHER MODELS ARE NOT LIKELY HANDLING INITIAL MCV OVER NRN FL WELL WHICH WOULD LIKELY IMPACT TIMING AND PLACEMENT OF HEAVIER PCPN DAY 1. SEE QPFPFD FOR PCPN DETAILS. ...WAVE IN NORTHWEST FLOW REACHING THE SOUTHERN PLAINS LATE FRIDAY... PREFERENCE: BLEND OF 00Z OPERATIONAL MODELS...INCLUDING 12Z NAM/GFS CONFIDENCE: AVERAGE THE NAM HAS COME INTO LINE WITH MOST MODELS WITH WEAK WAA EVENT OVER THE SRN PLAINS/LOWER MS VALLEY FRI INTO SAT MRNG IN RESPONSE TO WEAK IMPULSE/JET STREAK IN NW FLOW THRU THE CNTL U.S. A GENL MODEL BLEND HERE APPEARS ACCEPTABLE. ...DEEP TROUGH APPROACHING THE PACIFIC NORTHWEST... PREFERENCE: NON-NAM BLEND CONFIDENCE: AVERAGE THE NAM HAS TRENDED SLOWER BUT STILL REMAINS A SLIGHT FAST OUTLIER WITH THE MDTLY DEEP TROF APCHG B.C. AND THE PAC NW REGION SAT INTO SUN. WHILE SLIGHT TIMING/AMPLITUDE ISSUES EXIST AS THE SYSTEM PUSHES INTO THE PAC NW COAST SAT NIGHT INTO SUN..THE OVERALL SENSIBLE WEATHER IMPACTS DO NOT APPEAR TO BE LARGE. WAS A FAST OUTLIER AS EARLY AS 48 HOURS INTO THE FORECAST. OTHERWISE THERE WAS DECENT AGREEMENT AMONG THE GLOBAL MODELS ON THE LARGE SCALE. WITH THE EXCEPTION OF THE 12Z NAM..A GENL MODEL BLEND FOR SYNOPTIC DETAILS APPEARS USABLE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... SULLIVAN