Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1134 AM EST Wed Feb 26 2020 Valid Feb 26/1200 UTC thru Mar 01/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12z NAM/GFS Model Evaluation with Initial Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Eastern Half of North America... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The 12z NAM/GFS are close to the consensus taking the lead short wave in the evolving long wave trough from western TN into western PA this evening, before closing off over Ontario/Quebec after 28/00z. Secondary surface development occurs at the triple point of the lengthening occlusion over the southwest ME coast after 27/18z. There is good model consensus with fairly tight clustering with the surface low through this time. As the mid level system closes off over Quebec/northern ME through the end of the period, there is some spread on the track of the weakening surface low moving across the same area. The 12z GFS is the westernmost solution in the envelope by 01/00z, though by this time much of the sensible weather remains in Quebec. With the increasing model agreement, a general model blend is preferred, though some spread at the end of the forecast period keeps forecast confidence at average. ...Western U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-12z GFS blend Confidence: Average Evolving short wave energy near 46N 154W after 27/12z attempts to close off as it approaches WA state after 29/00z, before tracking into Alberta/Manitoba by the end of the period. The 12z GFS is faster than the consensus with the short wave almost immediately, with the greatest difference in timing occurring as it reaches the Pacific Northwest after 29/00z. The 00z NAM, by contrast, remains closer to the consensus throughout the period. After briefly closing off a mid level circulation over Vancouver Island near 29/00z (which the 12z NAM does 6 hours later), the 12z GFS begins slowing as it encounters mid level ridging over the Northern Rockies and west central Canada. By 01/00z, the 12z GFS rejoins the pack with the mid level feature and surface low over southern Manitoba. Because of its faster solution through the first half of the forecast period, the 12z GFS is omitted from the preference. Some spread in the placement of the surface low late, in addition to the timing issues with the 12z GFS, results in average forecast confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hayes