Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 313 AM EDT Fri Mar 20 2020 Valid Mar 20/0000 UTC thru Mar 23/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00z Model Evaluation with Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Low pressure and cold front crossing the Upper Great Lakes and Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average For the big surface low exiting the Great Lakes region Friday and the trailing cold front across the Appalachians and reaching the East Coast Friday night, a multi-deterministic model blend should suffice given good agreement on timing of cold frontal passage. ...Mid level troughs affecting the Northern Plains into the Upper Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/00Z ECMWF Confidence: Average For the first short wave tracking out of central Manitoba, the 00Z NAM is still a little stronger than the other guidance as it reaches North Dakota midday Saturday, but not to the degree indicated in earlier runs, and the 00Z CMC is slightly slower compared to the consensus with regard to timing. For the second short wave tracking from Alberta into the Northern Plains by Sunday morning, the 00Z NAM is more amplified with the wave and the UKMET is slightly slower. The GFS becomes more progressive by Sunday night as the wave crosses Minnesota. A blend of the GFS/ECMWF should serve well as a starting point in the forecast since they have good ensemble support. ...Mid level trough crossing the Southwest Saturday... ...Closed mid level low approaching Central California Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/00Z ECMWF Confidence: Average A lead shortwave trough approaching southern California Saturday morning is forecast to track across the Desert Southwest and reach the central Plains by Sunday. The deterministic models are in good agreement on timing through Saturday, with the exception of the slightly weaker EC mean. By Sunday morning the NAM is more amplified and is not favored. A closed mid level low follows behind this shortwave and wobbles toward the Central and Southern California coast by Sunday night. With this feature, the 00Z ECMWF trended faster although its mean is slightly slower than the other guidance by Sunday night, and the GFS is closer to the consensus timing compared to earlier runs. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick