Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 137 AM EST Sun Feb 24 2019 Valid Feb 24/0000 UTC thru Feb 27/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Phasing trough/closed low over Midwest/Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement with the strong closed low moving across IA which will lift northeast across the Midwest and Great Lakes region through Sunday. The system will be phasing with an intrusion of northern stream shortwave energy as it does so, and allowing for rapid surface pressure falls over the Great Lakes region and resulting in a large scale high-wind event that will impact large areas of the Great Lakes, OH Valley, northern Mid-Atlantic and Northeast Sunday into Monday. A general model blend will be preferred at this time concerning the mass fields with this system. ...Deep closed low/trough over the Pacific Northwest... ...Undercutting shortwave arriving over northern CA Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Average The guidance overall shows rather good agreement with the evolution of a slow-moving, positively tilted upper trough and developing closed low that drops over and just offshore of the Pacific Northwest by Sunday night through early Tuesday. A related surface low off the West Coast is expected to arrive across southwest OR by early Monday and move inland across the southern and then eastern portions of the state. There are some timing differences with this as the 00Z NAM is the slowest solution, but all of the global models are clustered toward a more progressive solution by comparison. As this energy quickly advances inland on Monday, there will be another system approaching the West Coast with a focus on northern CA by early Wednesday. This system will be the remnants of an upstream closed low that will weaken and undercut the evolving deep closed low over the Pacific Northwest, but there will be another surface low associated with this. The 00Z GFS is a bit more aggressive with this energy arriving over northern CA compared to the remaining model guidance which cluster toward a more dampened shortwave. The 00Z ECMWF is a bit faster with the timing of this feature compared to the other models, but there is some ensemble support for a more progressive solution. Accounting for the details and spread within the guidance, the preference right now will be to lean toward a non-NAM blend with all of the energy impacting Northwest and the West Coast for this period. ...Remainder of the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average The remainder of the country will feature northern stream energy dropping down across the northern Plains and Upper Midwest by Wednesday, as the southern tier of the country sees strong, zonal westerly flow along with an active subtropical jet (and embedded shortwave perturbations) impacting the Gulf Coast and FL Peninsula. The 00Z NAM appears too strong/amplified with its energy across the northern Plains and Upper Midwest, and is a bit out of tolerance with the global models across the South as it tends to back the mid-level flow a little more sharply. A non-NAM blend will be preferred across the remainder of the CONUS as a result. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison