Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1206 PM EST Wed Mar 06 2019 Valid Mar 06/1200 UTC thru Mar 10/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preference and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep trough over the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Deep cyclonic flow will remain in place over the Northeast US and New England through the end of the week. Another shortwave trough will work through the region later tonight into Thursday, with the only sensible weather impact being additional lake effect snows. Overall, model agreement is very high and a general model blend is preferred. ...Closed low in Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET, non-NAM blend Confidence: Slightly above average Closed low over the Northwest will slowly track eastward through the rest of this week. Overall, across the Northwest and Northern Rockies, model agreement is fairly good. A piece of the energy does shear off and become absorbed with the CA energy that leads to the strengthening weekend system (see below). There is fairly strong agreement with the ensemble guidance as well with the largest outliers being the 00z UKMET and 12z NAM. As a result, a blend not incorporating those 2 solutions is preferred at this time. ...Upper Midwest Deepening Surface Low This Weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Slightly below average A cyclone will develop in the lee of the Rockies Friday evening before lifting toward the Upper Midwest on Saturday as it rapidly deepens. This is in response to a strong negatively titled shortwave trough working through the Central Plains. There remains some spatial differences in the low track as it gets toward the Upper Midwest. The CMC is furthest NW, with its low center in NW Iowa compared to the GFS which is across eastern IA by 00z Sunday. The UKMET is further south while the ECMWF is a good compromise. Forecast confidence remains less than normal given some of the spread this far out. For now, a non-NAM blend is preferred with more weight given toward the GFS/ECMWF at this point. ...Next Pacific trough and surface low nearing Central West Coast Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00z ECMWF/UKMET, 12z GFS blend Confidence: Slightly above average Another shortwave trough will approach the West Coast by Saturday, apart of trough carving out across the Pacific Northwest. The models continue to slow its progression eastward, with most of the energy staying offshore. The GFS is a bit faster and also closes off closer to the coast compared to the 00z ECMWF/UKMET/CMC. The NAM is more of a consensus between the two solutions. Overall, given the slowing trend and looking at the ensemble guidance, a blend of the 00z ECMWF/UKMET with some of the 12z GFS is preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor