Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1235 PM EDT Tue Apr 16 2019 Valid Apr 16/1200 UTC thru Apr 20/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Model Evaluation...with Initial Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS and 00Z ECMWF/UKMET Confidence: Slightly above average The main weather maker across the CONUS through Friday is the long wave trough digging down the Great Basin today with the southern portion closing into a low as it crosses the southern Rockies late tonight into Wednesday. There is good agreement among the global deterministic models until late Wednesday when the 12Z NAM remains more amplified and the ECMWF is the least amplified on Day 2. However, through which has impacts on the heavy QPF across the southern CONUS in the Day 2/3 time frame. 12Z NAM/GFS remain close to the consensus as the long wave trough lengthens over the Southwest and Southern Plains during Day 2. The northern stream portion of the trough digs down the Great Plains on Day 2 which interacts with the southern stream portion Thursday night. The 12Z NAM is the strongest with the resultant low on Friday which makes for the slowest progression and is the largest outlier. The 12Z GFS became more progressive on Day 3 which is now a little faster than the 00Z ECMWF, but is still fairly close to the 00Z ECMWF/UKMET. The 00Z CMC is the second strongest with the low over the southeast on Day 3 which is a bit of an outlier compared to the preferred blend of the 12Z GFS and 00Z ECMWF/UKMET. There are some timing and amplitude differences with the next short wave reaching the Pacific Northwest on Friday. The 12Z GFS remains faster than the consensus, with the 00Z CMC much more amplified and the 00Z ECMWF slower. Since QPF is mainly topographically determined in the Pac NW the only notable difference among global deterministic guidance is the 00Z CMC, so a non-CMC blend is recommended for the Pacific Northwest for Days 2/3. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Jackson