Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1236 PM EDT Mon May 27 2019 Valid May 27/1200 UTC thru May 31/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Model Evaluation Including Initial Preferences and Forecast Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall CONUS Overview... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS and 00Z ECMWF/UKMET Confidence: Slightly Above Average An amplified and active weather pattern will continue over the CONUS through the next 3 days. The anomalous closed low moving northeast across the Four Corners region today and tonight will slowly move northeast across the central Plains Tuesday into Wednesday before being sheared and drawn into a deep cold core low over James Bay through Thursday as a secondary shortwave trough rounding the parent trough across the West catches up to the remnant low over the Midwest on Thursday. Meanwhile the strong subtropical ridge over the southeast US is slowly shunted south. Progression of this main low, the deep trough out west (with a shortwave trough rounding it) and the subtropical ridge suppression are all well handled by 00Z/12Z guidance with only minor details to the rate of decay of the low over the central Plains and timing of the shortwave trough in question. Particularly good agreement with these features is seen in the 12Z GFS and 00Z ECMWF/UKMET with very similar Day 2/3 QPF. The 12Z NAM is the strongest with the western shortwave trough as it digs south of AZ/NM on Wednesday and therefore has a slightly flatter QPF depiction for Day 2 across the southern Plains. This places the focus of QPF from the 12Z NAM on Day 3 farther east with the shortwave than the remnant parent low which is different than the consensus. The 00Z CMC maintains the closed parent low longest over the central Plains and therefore has a northward displacement of the main precip axis, into the Great Lakes for Day 3. Therefore the 12Z GFS and 00Z ECMWF/UKMET are preferred with slightly above average confidence. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Jackson