Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 124 AM EDT Tue Jul 07 2020 Valid Jul 07/0000 UTC thru Jul 10/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation with Model Preferences/Confidence Intervals ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS initialization errors do not seem to degrade their short range forecasts. New trough moving into the Pacific Northwest Thursday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Model Blend Confidence: Slightly above average The guidance shows general agreement with the depth and progression of this feature into Thursday afternoon, though there has been a slight quickening trend seen in the 12z Canadian and 12z UKMET solution which adds merit to the quicker 12z NAM forecast. A compromise of the 12z GFS, 12z ECMWF, 12z UKMET, 12z NAM, and 12z Canadian is preferred (which best fits in the 12z GEFS/00z ECMWF ensemble mean solutions) with slightly above average confidence. Closed low moving east along the western & central US/Canadian border ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-NAM compromise Confidence: Slightly 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 -- and the 12z UKMET becomes the quickest. Since the flow pattern in which it is embedded is fairly zonal, will prefer a compromise of the 12z GFS, 12z ECMWF, 12z UKMET, and 12z Canadian (which fits in well with the 12z GEFS/00z ECMWF ensemble mean solutions) with slightly above average confidence. Deep layer cyclone edging east-northeast near the VA/NC border ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Model Blend 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 12z Canadian has trended south while the 12z UKMET has shifted west a little, leading to converging guidance. The progressive ridge moving over the top of the system argues for a slower 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, agreeable with the current guidance. Will prefer a compromise of the 12z GFS, 12z NAM, 12z UKMET, 12z Canadian, and 12z ECMWF with above average confidence. Shortwave trough moving by New England Wednesday Weakening 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