Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1236 PM EDT Wed Aug 07 2019 Valid Aug 07/1200 UTC thru Aug 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Model Evaluation with Initial Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Model mass fields are in very good agreement into Friday Night, with the main issues with QPF on placement and magnitude along a slow moving cold front over the south-central CONUS on Friday and ahead of another cold front over the northern Plains on Saturday. A broad-based model blend is preferred for mass fields with higher resolution for QPF given their ability to place convective precip farther toward instability pools. A cold front stalls over the south-central CONUS late Friday with associated precip for Day 2 varied in placement and magnitude along this front. One note is the 06Z GEFS QPF mean and 00Z ECENS QPF mean are the farthest north while operational runs of those models as well as other deterministic guidance are farther south toward instability. However, the 3km NAM nest is in similar latitude (northern OK/AR) as the GFS/ECMWF, so the answer is not simply farther south. A broad based model approach to QPF is recommended to account for differences in the frontal placement which will be determined by convective processes. Differences in the synoptic scale begin to emerge Friday night with the progression of a trough into the West Coast. The 12Z GFS is the most progressive inland which would create differences in shortwave trough progression downstream around the northern high plains ridge axis to the trough over the northeast CONUS. However, little QPF difference is noted between the 12Z GFS and other 12Z/00Z guidance, so a general model blend is recommended. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Jackson