Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 110 AM EDT Tue Mar 31 2020 Valid Mar 31/0000 UTC thru Apr 03/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Central Plains shortwave and southern U.S. surface low... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model compromise Confidence: Above average Differences are relatively minor with this system resulting in a general model blend for the preference. However, the 00Z GFS appeared a bit too fast with the mid-level shortwave as it reaches the Southeast, and the 00Z NAM was the farthest north and/or west with the resultant surface low which tracks into the western Atlantic. The preferences is toward the latest ensemble means given good clustering from ensemble scatter low plots and spaghetti heights. ...Broad upper level gyre over Northwest... ...Shortwave "spoke #1" tracking from the northern High Plains into Saskatchewan/Manitoba Wednesday into Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/12Z ECMWF blend Confidence: Slightly below average The 00Z GFS is an eastern outlier with this feature, having trended even farther away from the edge of the ensemble spaghetti height plots early Thursday. The 12Z CMC is ill defined with this shortwave and is a weaker outlier with respect to ensemble spaghetti heights. The 12Z UKMET is a bit slower than the consensus. The best compromise at this time is of the stronger 00Z NAM and weaker 12Z ECMWF given they are in similar locations and in decent agreement from the ensemble means. ...Broad upper level gyre over Northwest... ...Shortwave "spoke #2" tracking from WA/OR Wednesday morning to the Northern Plains by Friday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/12Z UKMET blend Confidence: Below average The models have broad agreement on a positively tilted shortwave trough over the Great Basin for Thursday, ejecting out into the Northern Plains by Friday morning, perhaps as a negatively tilted trough. The 12Z ECMWF/CMC are faster than the remaining guidance with this feature with the 12Z CMC rather strong as well. The 00Z GFS is slower than the remaining consensus while the 00Z NAM and 12Z UKMET form a relatively good compromise in the middle of the available models. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto