Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1146 AM EST Fri Mar 6 2020 Valid Mar 6/1200 UTC thru Mar 10/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Initial model evaluation with preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overall Pattern Across the Continental United States ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12Z Sunday, then a GFS/ECMWF blend after Confidence: Slightly above average A synoptic scale trough initially over the northeastern U.S. is forecast to evolve into a closed upper low south of Nova Scotia by Saturday morning and support a rapidly developing oceanic surface low through Saturday night, with the vast majority of the impacts confined to the offshore waters. There is now enough model agreement with respect to speed and placement to merit a multi-model deterministic blend for this event. In the wake of that system, upper level ridging and surface high pressure dominates much of the central and eastern U.S. for the upcoming weekend. By Saturday night, a shortwave trough reaches California and tracks across the Intermountain West and then reaches the western High Plains by Monday, at which point the GFS is more progressive with the trough and the NAM/CMC are a little less amplified. At the surface, the 00Z UKMET appears displaced farther north than the model consensus. A second system is progged to reach the Pacific Northwest Sunday morning and track eastward near the Canadian border through Monday night, with the NAM a bit more amplified and faster, and the GFS is slower than the model consensus. A closed upper level low then meanders off the California coast at 84 hours, but its influence on sensible weather holds until after the period. Overall a general model blend is favored through 48 hours, then a ECMWF/GEFS mean blend should serve well as a starting point in the forecast process. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick