Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 343 PM EDT Wed May 15 2019 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 with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Low pressure and trough moving across the West to the Southern Plains by Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z ECMWF/UKMET/NAM Confidence: Slightly above average Low pressure moves into the far northern CA coast tonight, opens into a trough centered over the Great Basin Thursday night, digs to the southern Rockies Friday night and onto the southern Plains Saturday. 12z guidance is in decent agreement with this progression with the main differences the depth and intensity of the trough over the northern Rockies. The 12z UKMET/CMC no longer close the low over the southern plains on Saturday, but they both close the mid-level low over WY Friday night which is earlier than the GFS/ECMWF/NAM. The 12z GFS closes this low over the northern plains on Day 3 which draws the surface low farther north. The 12z ECMWF and UKMET have similar trough structure to the 12z NAM which is flatter over the southern plains with a surface low over western OK by 19/00z while the 12z CMC is more progressive. There is good agreement in QPF with the 12z ECMWF/UKMET/NAM on Day 3 which is preferred. Since the 12z GFS/CMC which have the Day 3 heavy rain displaced farther north into the central plains rather than TX/OK like the rest, they are not preferred. ...Overall Pattern for the rest of the US focusing on the northern CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Above average Good 12z agreement on a shearing low over Hudson Bay that ejects southeast across northern Ontario Thursday night and crosses New England Saturday and a low over New England today lifting north with a resultant trough over New England through Thursday. The synoptic ridge axis up the Great Plains into the Canadian Prairies persists through Friday and focuses a northwesterly jet stream from the Canadian Prairies to New England and allows weak disturbances to result in precip from MT across the southern Great Lakes for both Days 2 and 3. 12z precip axes are rather similar for the most impactful areas such as the southern Great lakes on Day 2 and the northern plains into the upper Midwest on Day 3. Even the lighter QPF areas have good agreement such as northern Maine where in spite of the 12z NAM having a lagging surface low, there is little impact to the QPF placement. Therefore a general model blend is preferred. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Jackson