Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1146 PM EST Sun Nov 25 2018 Valid Nov 26/0000 UTC thru Nov 29/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z NAM/GFS Evaluation...with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM...00Z GFS...12Z ECMWF blend Confidence: Average The upper pattern starts off rather amplified over the lower 48 with broad troughing off of the Pacific Northwest, followed by sharp upper ridging over the Pacific Northwest into western Canada and longwave troughing over the Great Lakes/Mid-Mississippi Valley. A powerful shortwave responsible for ongoing blizzard conditions over portions of the upper Midwest will track toward the Northeast with secondary low development over New England early Tuesday morning. Meanwhile a large closed low will form over the Great Lakes and track eastward through Wednesday night as it reaches Nova Scotia. The flow pattern over the western U.S. will flatten into mid-week before the arrival of a powerful shortwave to reach northern California early Thursday morning. Out West, the biggest difference was with the approach of a strong shortwave and surface low toward northern California early Thursday morning. The 00Z GFS has held decent run to run continuity over its past 3 cycles with a broad trend from the other models toward the GFS since 3 cycles back. Ensembles show the 12Z UKMET/CMC to be a bit slow and the ensemble scatter low plots have been trending south valid 12Z Tuesday. While the 00Z GFS is just south of the middle of the latest ensemble scatter low plots, it has held good continuity and when blended with the 00Z NAM and 12Z ECMWF, a favorable middle ground is reached. The models were fairly agreeable with the evolution of the storm system approaching the Great Lakes and redevelopment for New England. Ensemble scatter low plots still show some room for adjustment with the 00Z GFS/18Z GEFS along the western side of the model spread Northeast early Tuesday but the trend since yesterday has been to take the low farther inland. A general model blend appears reasonable here. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto