Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1259 PM EDT Wed May 01 2019 Valid May 01/1200 UTC thru May 05/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM, 12Z GFS, 00Z ECMWF blend Confidence: Average The upper level pattern across the nation through Saturday evening will feature a longwave trough over the north-central U.S. with a series of shortwaves to travel through the base of the trough. A southern stream jet in place from the Baja Peninsula into the Southern Plains and then northeastward toward the Mid-Atlantic region will carry a number of shortwaves, some of which will be convectively driven, with waves of low pressure moving along a frontal boundary draped from roughly the Northeast to Texas. Regarding the timing of shortwaves through the central U.S. around the longwave trough across the North and through the southern stream jet over Texas, a 12Z NAM timing appeared best, closer to the middle of the somewhat faster 12Z GFS/GEFS and slower 00Z ECMWF. The 00Z CMC showed the least support from remaining available guidance and the 00Z UKMET was in the middle with shortwave timing but appeared to have a convective feedback bulls eye originating over Texas/Arkansas on Thursday which carries through into the Ohio Valley and Northeast. A 700-500 mb wave currently over the Caribbean shows good agreement in the ensemble means best represented by a 12Z NAM, 00Z ECMWF, 00Z UKMET blend with the 00Z CMC significant faster/north while the 12Z GFS is slightly faster/north than the better ensemble consensus. Outside of the 00Z CMC, the bulk of the heaviest precipitation appears to stay offshore from this feature, so even the 12Z GFS does not appear too deviant of a model when included as part of a blend. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto