Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1244 AM EDT Wed Jun 24 2020 Valid Jun 24/0000 UTC thru Jun 27/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low over Ontario/Quebec Trough crossing the eastern U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The upper level low in place over the northern Great Lakes is expected to lift north/northeastward over the next few days while there will be some southward expansion on the longwave trough over the eastern U.S., which pushes a cold front through much of the Mid-Atlantic and New England before washing out over the Southeast. From a synoptic point of view, mass fields are in good shape in the region and a general model blend is preferred. Shortwave crossing the Pacific Northwest and Plains Energy digging into the Southwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS, 12Z ECMWF Confidence: Average Guidance has trended better over the last few runs and now shows fairly good agreement in the synoptic pattern as a shortwave trough skirts across the Pacific Northwest into the northern Rockies. The UKMET is a faster outlier and while the GFS is on the slower side of the guidance, it is closer to the overall means and ECMWF/NAM. Bigger differences are noted on the southern end, where some of the models advertise some energy separating out and digging further south over southern California. The ECMWF holds back the energy the most while the GFS is a bit flatter/faster. Given the two areas of differences, from a mass field perspective, a blend of the GFS/ECMWF/NAM is preferred. Lower to Mid MS River Valley...Deep South ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the ECENS/GEFS/CMC/NAM Confidence: Below Average Weak flow aloft with pieces of shortwave energy becoming removed from the westerlies will drift over the Texas gulf coast and lower MS Valley. The models are struggling with what to do with this energy as it attempts to get lifted back northeast into the larger longwave trough. The UKMET is the most aggressive with this idea, developing a stronger shortwave over the Southeast toward the NC coast by the end of day 3. The other models all have some flavor of holding the energy back, closer to the Gulf Coast, which is generally favored. The ECMWF/NAM show the slowest/western solution while the GFS tries to lift it northeast by day 3. Given the messy mass fields and weak flow generally, the sensible weather is also messy and low confidence. As such, the day 2 and particularly the day 3 preferences for a heavy weight of the ECENS/GEFS means with some inclusion of the CMC/NAM Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor