Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1212 AM EST Thu Mar 05 2020 Valid Mar 05/0000 UTC thru Mar 08/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model preliminary evaluation with final preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deepening northern stream low moving out of the Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z UKMET/ECMWF/ECENS/CMC through 36 hours, 12Z UKMET/ECENS/ECMWF thereafter Confidence: Slightly above average A southern stream wave lifting out of the Gulf Coast will weaken today as the northern stream becomes dominant. Shortwave moving across the Great Lakes will deepen into a closed low as it digs southeast towards the Mid-Atlantic Friday. The GFS/NAM are well aligned with the translational speed of this feature, as well as the intensity, but they are both slower than then non-NCEP consensus, and the GEFS mean. The non-NCEP suite is in very good agreement with the low deepening to a closed low tonight, with slight interaction with the southern stream impulse Friday. This will lead to an area of deformation across upstate NY and southeast into the Mid-Atlantic, with some enhanced QPF. The CMC beyond 36 hours features a significant capture of the southern stream impulse, leading to an eastward shift and strong wrap up of the closed low, and spreads QPF much further north and west into New England. This is a clear outlier and should be used with caution beyond 36 hours. ...Longwave trough moving into the West Coast Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Slightly above average A deepening longwave trough dropping from the Gulf of Alaska will approach the Pacific Northwest today and then extend down towards the CA coast Friday before lifting onshore by the weekend. The NAM is much sharper and deeper with this feature when compared to the other available guidance, which are otherwise well clustered, and tries to pivot the southern periphery of the trough negatively into CA. While this feature weakens quickly after coming onshore, the significantly different strength of the NAM leads to its exclusion from the preference. Otherwise, the remaining guidance all seems reasonable. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Weiss