Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 302 PM EDT Fri May 03 2019 Valid May 03/1200 UTC thru May 07/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...General overview of the CONUS through 00Z/07... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z UKMET/ECMWF Confidence: Slightly above average ...19Z update... Across the eastern U.S., the 12Z ECMWF adjusted a little flatter with the mid-level shortwave approaching the Mid-Atlantic region while the 12Z UKMET only made minor adjustments (slight shift north with surface low) compared to their previous 00Z cycles. The 00Z meanwhile adjusted less amplified but it's surface low is displaced some from the remaining consensus. Across the Northwest, the ECMWF/UKMET/CMC adjusted toward the somewhat similar 12Z NAM/GFS with the amplitude and timing of the shortwave early Monday. Otherwise, changes across the CONUS were minor. ...previous discussion follows... A longwave trough that covers most of the northern half of the nation from the Northwest to the Great Lakes will flatten some and slowly edge east over the next 3 days. Meanwhile, a weak southern stream perturbation will enter Texas later today and reach the East Coast for Sunday as a closed low reaches California. There is broad agreement with the mass fields for many of these features but there are two differences worth noting. First, the ensembles show better agreement with the 00Z ECMWF/UKMET with the shortwave tracking from Texas to the East Coast and the resulting frontal wave near the Mid-Atlantic region for Sunday. The 00Z CMC is more amplified as is the case with other features in the northern stream and is not preferred. The 12Z NAM/GFS meanwhile show timing differences with the 12Z GFS significantly faster. The other feature to note is across the Northwest with a shortwave amplifying toward the northern Rockies by Monday. Here, the 00Z ECMWF/UKMET show more amplification in the base of the trough compared to the flatter 12Z NAM/GFS, with the ensemble means more closely aligning with the ECMWF/UKMET solutions. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto