Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1226 AM EDT Sun Apr 08 2018 Valid Apr 08/0000 UTC thru Apr 11/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z GFS/NAM evaluation with preliminary model preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM initialization errors do not seem to degrade their short range forecasts. System weakening as it approaches West Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-Canadian blend; slightly above ave confidence The 12z Canadian was a slow outlier with this system's progression -- its usual bias. A compromise of the strong 12z ECMWF, 12z UKMET, 00z NAM, and 00z GFS is preferred to deal with lingering detail issues with slightly above average confidence. Strong closed low and trough impacting Northwest through Sun Shortwaves composing amplifying trough moving into East Low offshore the East coast Monday into Wednesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend; confidence slightly above ave The 00z NAM is deeper/broader with an initial shortwave moving through the East on Tuesday which leads initially to a more northerly, and then easterly low track between Bermuda and the East coast. It is unique within the deterministic and 12z global ensemble guidance and is not preferred. Otherwise, despite the 00z GFS slightly flatter and quicker upper trough progression by Wednesday morning, the remainder of the guidance is in good agreement on the surface low track. A compromise of the 12z UKMET, 12z ECMWF, 00z GFS, and 12z Canadian is preferred with only average confidence as the 12z global ensemble guidance shows greater dispersion than normal offshore NC. This should also help resolve difference in light precipitation across the central Plains Monday morning. Shortwaves moving across the Great Lakes Monday/Tuesday morning System lifting out of New England into Atlantic Canada tonight Deepening cyclone moving offshore East coast Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The guidance shows good agreement with these systems. A compromise of the 00z GFS, 00z NAM, 12z ECMWF, 12z Canadian, and 12z UKMET is preferred with above average confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Roth