Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 130 PM EST Sat Mar 09 2019 Valid Mar 09/1200 UTC thru Mar 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Positively tilted shortwave trough moving east into Manitoba and Ontario this weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model compromise excluding 09/12Z UKMET Confidence: Slightly above average The 12Z guidance largely kept continuity with this feature, leaving the 09/12Z UKMET on the slow/sharper side of the guidance. The 12Z Canadian continued toward the consensus value and is probably in good enough position to be included in the blend. ...Surface low tracking across the Upper Midwest/Great Lakes through Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model compromise excluding the 09/12Z UKMET/NAM Confidence: Slightly above average Overall, the models and the ensemble guidance remained in fairly good agreement with this system, but the Canadian remains displaced west of the consensus with its 500 mb low by Sunday morning over the Great lakes region and the NAM appeared to be overly aggressive with a trailing shortwave that closes off a mid-level low briefly near the western tip of Lake Superior at the start of the Day 2 forecast period. Otherwise, a blend of remaining models tends to show good agreement and is recommended here. ...Closed low over Washington this morning, interacting with the next Pacific trough/surface low nearing California later today, developing into a large closed low over or just offshore of California Monday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The 12Z NCEP guidance maintained good continuity with the large scale picture and the smaller scale details from their earlier runs...thus maintaining a good degree of agreement between the operational runs, ensemble guidance and the latest non-NCEP runs. Made no change to the model preference. ...Progressive upper trough approaching the Pacific Northwest Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 09/12Z NCEP/ECMWF blend Confidence: Average Model agreement was not as good with this system compared with the ones above. The ensemble means differ on the timing of the next shortwave trough to affect the Pacific Northwest Monday night into Tuesday. The 12Z NCEP and ECMWF models were closest to the ensemble means, which is probably the best place to be given the spread in the guidance. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Bann