Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1213 PM EDT Thu Mar 14 2019 Valid Mar 14/1200 UTC thru Mar 18/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Powerful deep closed low exiting the Midwest/Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show very good agreement in taking the deep layer closed low over the Midwest northeast across the Great Lakes tonight and then across southeast Canada on Friday. Meanwhile, a trailing cold front will sweep across the eastern U.S. with the front moving off the East Coast Friday night with exception of the lower part of the FL Peninsula where the boundary is expected to slow down and only gradually shift south. Given very good model mass field agreement, a general model blend will be preferred. ...Shortwave energy over the northern Plains/Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Slightly above average In the wake of the exiting deep cyclone over the Midwest and Great Lakes will be an intrusion of northern stream shortwaves from southern Canada which will cross the northern Plains and Midwest through the weekend. The 12Z NAM is overall a bit sharper with the shortwave impulses and consequently drives a bit heavier QPF versus the global models. Will recommend a non-NAM blend at this point given the reasonably good global model mass field agreement. ...Weak upper trough reaching the West Coast tonight... ...Digging into the Southwest on Fri/Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-ECMWF blend Confidence: Above average A weak upper trough will approach the West Coast by tonight and then separate out from the westerlies and dig into the Southwest on Friday and Saturday. The guidance agrees in developing a weak closed low feature over AZ by early Saturday, with the closed low then gradually elongating and shifting off to the east across portions of NM through Sunday. The 00Z ECMWF is overall the deepest solution with the closed low, and especially by Sunday. As a result, the ECMWF is also a bit wetter than the remaining guidance. Given reasonably good model mass field agreement seen otherwise, a non-ECMWF blend will be preferred. ...Shortwave over the northern Rockies by Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-GFS blend Confidence: Above average The 12Z GFS is a stronger outlier with the shortwave rounding the mean layer ridge along the West Coast on Sunday and dropping down over the northern Rockies. The remaining guidance is rather well clustered, so a non-GFS blend will be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison