Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 154 PM EST Fri Mar 08 2019 Valid Mar 08/1200 UTC thru Mar 12/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Final Preference and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Departing shortwave over the eastern U.S. today... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model compromise Confidence: Above average The models remained good agreement with their previous runs and with each other. The 12Z NAM remains on the deeper side of the guidance while the 08/00Z Canadian was flattest. Otherwise, the differences are small, and a general model compromise is preferred. ...Shortwave initially in Alberta/Saskatchewan tracking east and merging with another shortwave from the north over Saskatchewan/Manitoba on Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 08/12Z CMC blend Confidence: Average The 12Z NCEP guidance was comparable with their previous runs. The 08/12Z Canadian largely maintained continuity with its previous run...which leaves it on the slower/stronger side of the guidance with the positively tilted trough axis over western Ontario late Sunday. A non 08/12Z CMC blend is still preferred. ...Surface low tracking across the Upper Midwest/Great Lakes this weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 08/12Z CMC blend Confidence: Slightly above average Overall, the trend towards converging solutions has continued as the start of the event approaches with only modest changes noted in the 12Z suite of numerical guidance when compared with their previous runs. The 08/12Z Canadian was only a bit weaker than its previous run, so it remains one of the stronger solutions while the 08/12Z ECMWF sped up a small amount and was slower than the NCEP guidance but closer to the ensemble mean. For timing and strength purposes, a non 08/00Z CMC blend will work. ...Closed low over Washington this morning, interacting with the next Pacific trough/surface low nearing California on Saturday, developing into a large closed low over or just offshore of California Monday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 08/12Z NAM/GFS/ECMWF blend Confidence: Average Several pieces of energy coming out of the eastern Pacific will eventually carve out a deeper trough over the west coast late in the weekend, while interacting with a retrograding closed low over the Pacific Northwest. There is fairly good agreement with a surface low tracking south off of the West Coast and the eventual formation of a large closed low that develops near the California coast. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Bann