Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1249 AM EDT Thu Aug 13 2020 Valid Aug 13/0000 UTC thru Aug 16/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Preliminary Model Evaluation Including Preferences and Forecast Confidence ...Longwave trough moving from the Northwest to the Western Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GEFS/ECENS/NAM/CMC blend Confidence: Average An upper level trough with an embedded strengthening vort max digging through its base will move from the NW through the Western Great Lakes by Saturday. The key feature here is that vort max which may spawn a wave of low pressure and will drag a cold front eastward beneath it. Other than the GFS, which is a bit fast, the timing envelope is small among the global models. However, the ECMWF is a shallow solution compared to the other solutions, while the UKMET produces QPF which is quite a bit higher than any other solution. A compromise of the GEFS/ECENS/NAM/CMC leaves a reasonable solution for the progression and amplitude of this feature, with heavy rainfall possible across the upper midwest associated with this trough. ...Large trough developing across the eastern CONUS through Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GEFS/ECENS/SREF/CMC Confidence: Below Average An upper level trough will gradually envelop the entire eastern CONUS, while a shortwave ridge blossoms into southern Canada. This leaves a weakness in the height fields across the Ohio Valley into which a secondary trough or even a closed low may develop Saturday. There continues to be quite a bit of spread in both the amplitude of this trough, and position/intensity of the mid-level wave/closed low developing in the Ohio Valley. There are also significant differences which arise by Saturday across New England owing to the position of the shortwave ridge and its interaction with the OH VLY feature. The deterministic models are all over the place, but the GEFS/SREF means suggest a rather similar evolution so are weighted heavily in the blend. Despite being more shallow, the ECENS has shown decent consistency, and of the deterministic models the CMC is the one which most closely resembles the preferences from the means. However, at this time there remains below average confidence, and while a trough across the east seems likely, its intensity, and where the secondary low may develop to enhance rainfall potential, remain quite uncertain. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml This product will terminate August 15, 2020: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Weiss