Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1245 AM EDT Mon Mar 16 2020 Valid Mar 16/0000 UTC thru Mar 19/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep upper trough/closed low impacting the West... ...Cyclogenesis over the central High Plains Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours Non-NAM blend...after 60 hours Confidence: Slightly above average A deep upper trough and embedded closed low along the West Coast will continue to settle south over the next couple of days, and then begin to pivot inland into the Intermountain West by Wednesday which will foster lee-side cyclogenesis over the central High Plains. The guidance is in good agreement through about 60 hours, but thereafter the 00Z NAM tends to edge its height falls faster off to the east which fosters stronger low pressure development over eastern CO and southwest NE. The global models, especially led by the non-NCEP guidance, is a bit slower and not quite as deep with low pressure by the end of the period over the central High Plains. The consensus of ensemble guidance supports a non-NAM blend at this point, and so this will be the preference after 60 hours. A general model blend should suffice prior to this. ...Trough crossing the Upper Midwest/Great Lakes by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A northern stream trough will cross the northern Plains, Upper Midwest and Great Lakes region by Tuesday, with an accompanying cold front sweep from the Midwest into the eastern U.S. This front will then sweep off the East Coast by Wednesday as the upper trough quickly exits the Great Lakes and crosses the Northeast. Given good model agreement, a general model blend will be preferred at this time. ...Trough arriving over the northern High Plains Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The models bring a second northern stream trough down toward the northern High Plains by late Wednesday. The 00Z NAM is a bit slower and deeper than the global models with this system. Given the good global model agreement, a non-NAM blend will be preferred with this system. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison