Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1229 AM EDT Tue Oct 15 2019 Valid Oct 15/0000 UTC thru Oct 18/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Initial Model Evaluation with latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Great Lakes closed low and Northeast surface low ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12Z Thursday, then GFS/ECMWF/EC mean Confidence: Average A potent and progressive northern stream shortwave currently over the northern Plains is forecast to evolve into a closed low over the western Great Lakes region by Tuesday evening. It will continue to deepen as it tracks eastward and reaches New England by Thursday morning, acquiring negative tilt in the process. This will support the development of a nor'easter over the Gulf of Maine as the triple point low becomes the dominant low by 12Z Thursday. The deterministic models indicate good overall agreement through about 12Z Thursday. Beyond that time, the 00Z NAM becomes much slower with the low and loses ensemble support. Meanwhile, the 18Z GEFS mean is a bit to the east of the model consensus during this same time. A blend of the GFS/ECMWF/EC mean works well for the last 24 hours of the forecast period. Short wave energy affecting Texas through midweek ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: NAM/CMC/ECMWF blend Confidence: Average A southern stream shortwave trough over the Desert Southwest on Tuesday is expected to become detached from the westerlies. It should slowly track eastward across New Mexico and western Texas while embedded within an upper level ridge. This will support an inverted surface trough over the western Gulf Coast by Thursday. The 00Z GFS is displaced to the east of the model consensus whilst the UKMET is on the western edge of the guidance. The NAM, CMC, and ECMWF appear relatively well clustered across Texas and a blend of these should work well as a forecast starting point. Western U.S. longwave trough ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The upper level ridge over the western U.S. at the beginning of the forecast period will progress eastward across the Plains by midweek as a longwave trough approaches the West Coast. A lead shortwave perturbation will quickly pass across British Columbia Tuesday night, followed by a much stronger shortwave arriving by Wednesday evening. This will spur the development of a surface low and cold front across the Intermountain West that should reach the central and northern Plains by Friday morning. There is enough model agreement to support a general model blend for this trough. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Hamrick