Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 249 AM EDT Thu Oct 10 2019 Valid Oct 10/0000 UTC thru Oct 13/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Final Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Northeast states... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General blend through 00Z Saturday, then NAM/ECMWF/UKMET Confidence: Near Average A nor'easter situated just east of the 40N/70W benchmark has generally leveled off in intensity and is forecast to make a slow counter-clockwise loop over the next couple of days before tracking farther out to sea. This storm is blocked by a large surface to mid-level high over eastern Canada and part of a Rex block pattern. The 12Z ECMWF and its ensemble mean are slightly stronger with the low compared to the GFS and its ensemble mean. The 00Z GFS is in good agreement through about Friday evening, after which it tracks farther to the south during its cyclonic loop near 70W, and this continues going through Saturday. The 00Z ECMWF and its mean are slightly to the north of the model consensus and does not have the system making as large of a loop before pulling away from the coast. Therefore a general model blend works well through 48 hours, and then a NAM/EC mean/UKMET/ blend after that. ...Central U.S. Mid-Latitude Cyclone... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above Average An impressive upper level trough and closed low over the north-central U.S. is spawning cyclogenesis over the western High Plains and will support a rapidly developing surface low that will track from Kansas to northern Minnesota by early Saturday. This will be accompanied by a pronounced cold front and precipitous drop in temperatures across much of the Plains, along with potentially record snowfall for parts of the Dakotas and northwestern Minnesota. The models remain in very good agreement with this large scale storm system through the forecast period. The GFS does become slightly more amplified by Friday across the central Plains and Midwest and then becomes stronger with the surface low near the Canadian border, but close enough to be incorporated into the forecast. The 00Z UKMET has come into better timing agreement with the cold frontal passage across the Great Lakes and Ohio Valley compared to its 12Z run. ...West Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of ECMWF/EC mean/CMC Confidence: Average A complicated merger of two streams west of 130W eventually leads to a more consolidated open trough approaching the west coast by Saturday night into Sunday. The NAM becomes more progressive with the trough axis over the Pacific Northwest by Saturday night and stronger with the southern portion off the coast of California, and the UKMET is weaker compared to the model consensus. The 12Z EC mean is now among the strongest with this overall trough given a trend to slightly less amplified solutions during the 00Z model run cycle. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Hamrick