Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 236 PM EDT Fri Apr 10 2020 Valid Apr 10/1200 UTC thru Apr 14/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep cyclone exiting the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The anomalously deep closed low impacting the Northeast today will be ejecting northeast across southeast Canada tonight and Saturday. The guidance shows very good large scale agreement with the mass-field evolution, so a general model blend will be preferred as this system begins to exit. ...Closed low exiting the Southwest... ...Energy ejecting toward the lower MS Valley by Sunday... ...Powerful surface low over the Great Lakes by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/12Z UKMET/00Z ECMWF and ECENS/GEFS blend Confidence: Average...through 60 hours Becoming below average...after 60 hours The large, slow-moving cut-off southern stream low over southern California will gradually move toward southern AZ/NM on Saturday and then open up into a progressive shortwave across the southern Plains by early Sunday. By late Sunday, this energy will begin to take on a negative tilt over the lower MS Valley and quickly reach the OH Valley by early Monday. The energy coupled with increasing influence from a strong northern stream trough amplifying over the Upper Midwest Sunday and Monday will lead the way for a powerful surface cyclone to lift over lower MI on Monday. The guidance has generally come into better agreement with the evolution of the shortwave energy across the South, with multi-cycle trends of the GFS coming in slower and toward the non-NCEP model camp. Today's differences are much more focused on the OH Valley and Great Lakes region. The 12Z NAM ends up with a somewhat faster shortwave progression up north across the OH Valley into lower MI, and a low track on the left side of the deterministic model spread. The 12Z CMC overall is an outlier in being the weakest solution but also reflects a track farther northwest across the western Great Lakes. The 12Z ECMWF though which had been farther southeast has made a sizable jump with its track to the northwest and toward the NAM/CMC camp. However, the 00Z ECENS/12Z CMCE suites and especially the 00Z/06Z/12Z GEFS suites favor a solution that is quite deep, but with a low track still southeast of the 12Z NAM/CMC/ECMWF solutions. Having said that, there is a camp of EC ensemble members that do take the low off farther to the northwest, and the key for this to verify will be the intrusion of stronger northern stream energy from the Upper Midwest and subsequent phasing. The new ECMWF reflects this possibility. Confidence is somewhat limited late in the period as there is room for a somewhat deeper low to track farther west over the Great Lakes, but based on the latest clustering from the 12Z GFS, 12Z UKMET, and former 00Z ECMWF solutions, a blend of these solutions will be preferred, and in conjunction with the ensemble means. ...Amplifying upper trough over the northern U.S. by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models bring amplifying shortwave/jet energy southeastward from the southern coast of AK and the adjacent Yukon territory down across southwest Canada and out across the northern Rockies and northern Plains by Sunday. By Monday, this energy will amplify into a deep longwave trough over the northern U.S. that will gradually phase with the aforementioned southern stream energy ejecting across the South and lifting toward the Great Lakes region. The models are in good agreement with the details of the longwave trough evolution. So, a general model blend will be preferred with this. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison