Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 103 AM EDT Sun May 10 2020 Valid May 10/0000 UTC thru May 13/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Exiting deep layer cyclone impacting the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement with the details of the deep layer cyclone currently impacting the Northeast, which will be lifting off to the northeast across the Canadian maritimes through tonight and Sunday. A general model blend is preferred. ...Compact shortwaves/surface low impacting the northern Plains and Midwest this weekend... ...Energy amplifying from the OH Valley to the Northeast Mon and Tues... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The guidance takes the vigorous compact shortwave and associated surface low over the northern Plains southeastward across the Midwest going through Sunday. On Monday this lead energy and a fast-moving secondary shortwave in its wake will consolidate and transit the OH Valley. As the energy rounds the base of the larger scale troughing that will be persisting from the Great Lakes region into much of south-central and southeast Canada, this OH Valley energy should amplify, and by Tuesday all of the models support the idea of a negatively tilting shortwave and possible closed mid-level low crossing New England along with an intensifying surface low center. Early trends in the 00Z models suggest models are moving into better agreement with their handling of this consolidating shortwave moving from the Ohio valley into the Northeast on Monday. The NAM which had shown a more amplified shortwave moving from Canada into the Northeast late Tuesday, has backed away some from that solution with its 00z run - putting into better agreement with the overall model consensus. The GFS has also trended toward the consensus as well. While its 12Z run was faster than most models lifting the shortwave across the Northeast late Monday into early Tuesday, the 00Z GFS is now slower. This puts most of the deterministic guidance into fairly good agreement through 12Z Tuesday as the leading feature moves from northern New England into the Canadian Maritimes. ...Shortwave energy crossing the Southwest this weekend... ...Energy shearing across the southern Plains by Tues... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models show a weak shortwave crossing the Desert Southwest on Sunday. This energy is then expected to gradually shear off to the east and reach the southern Plains by Tuesday and the lower Mississippi valley by early Wednesday. While differences in the finer details persist - with low predictability regarding the timing/amplification of the embedded energy moving across the southern Plains - overall spread with respect to the larger scale pattern is modest. ...Upper trough/closed low lifting along the Northwest Coast Mon-Tue... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS and 12Z ECMWF Confidence: Slightly above average An upper trough and associated closed low will be approaching the West Coast by Tuesday as the larger scale blocking pattern across western North America begins to break down. The NAM remains the general outlier here - bringing an upper low over western Canada farther west, drawing the low off of the coast farther east than the model consensus. Nevertheless, all of the models increase the onshore flow into the West Coast, especially from northern CA to the Pacific Northwest as surface low pressure lifts northeast up off the coast. Based on very good model mass field clustering and ensemble support, a blend of the GFS and 12Z ECMWF remains preferred at this point. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Pereira/Orrison