Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1222 PM EDT Mon Jul 06 2020 Valid Jul 06/1200 UTC thru Jul 10/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z GFS/NAM Evaluation with Preliminary Model Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ NAM/GFS initialization errors do not seem to degrade their short range forecasts. New trough moving into the Pacific Northwest Thursday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM compromise Confidence: Above average Outside of the quick 12z NAM, the guidance shows good agreement with the depth and progression of this feature into Thursday afternoon. A compromise of the 12z GFS, 00z ECMWF, 00z UKMET, and 00z Canadian is preferred (which best fits in the 06z GEFS/00z ECMWF ensemble mean solutions) with above average confidence. Closed low moving east along the western & central US/Canadian border ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-NAM compromise Confidence: Above average The guidance shows good agreement with this feature moving east from the Pacific Northwest through Tuesday night before the 12z NAM becomes a slow/deep outlier in south-central Canada -- its traditional bias. Since the flow pattern in which it is embedded is fairly zonal, will prefer a compromise of the 12z GFS, 00z ECMWF, 00z UKMET, and 00z Canadian (which best fits in the 06z GEFS/00z ECMWF ensemble mean solutions) with above average confidence. Deep layer cyclone edging east-northeast near the VA/NC border ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-Canadian Compromise Confidence: Above average A deep layer cyclone is expected to move slowly east-northeast as a mid-level ridge builds to the north across the northern Appalachians and New England. The 00z Canadian was north of the other guidance while the 00z UKMET was the most eastward/quickest. The progressive ridge moving over the top of the system argues for slowly progression than the UKMET. The apex of the northern stream ridge (56-57N) argues for the latitude of the closed cyclone underneath for be centered in the 36-37N range, south of the 00z Canadian. Will prefer a compromise of the 12z GFS, 12z NAM, 00z UKMET, and 00z ECMWF (which naturally weights towards the slower guidance) with above average confidence. Shortwave trough moving by New England Wednesday Persistent 700 hPa trough across NV/CA through Thursday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The guidance shows good agreement with the progression and depth of these features, so prefer a compromise of the 12z NAM, 12z GFS, 00z UKMET, 00z Canadian, and 00z ECMWF with above average confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Roth