Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 247 AM EDT Sun Oct 13 2019 Valid Oct 13/0000 UTC thru Oct 16/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Final Model Evaluation with latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Deep Plains/Upper Midwest Cyclone ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The anomalously deep layer cyclone over the north-central U.S. will gradually weaken as it lifts northeastward across Ontario, Canada over the next couple of days. The initial cold front from this low has reached the East Coast but is forecast to stall across the Southeast on Sunday and going into Monday, and a secondary cold front crosses the Great Lakes and Ohio Valley through Sunday night. The models remain well clustered with this system and therefore a deterministic model blend is preferred. Pacific Northwest to the Great Lakes through Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM consensus Confidence: Slightly above average The next feature of interest to affect the western U.S. will be a progressive upper-level trough and associated cold front that should reach the West Coast by early Sunday, and then advance inland across the northern Rockies on Monday. By Monday night, the height falls start arriving across the High Plains and induces lee-side cyclogenesis over the central Plains to Upper Midwest. The GFS and ECMWF global models are fairly aligned with their ensemble means. However, the NAM becomes too amplified over the northern Plains by Tuesday morning and even more so by Wednesday morning, so a GFS/ECMWF compromise is a good starting point. Southwestern U.S. to southern Plains ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: EC mean/GFS/UKMET Confidence: Average Troughing moving through the western US will eventually pinch off a southern stream shortwave across southern California early Monday. It remains the case that the CMC and now the 00Z ECMWF are more amplified aloft across the Southwest early in the week compared to the other guidance. By Tuesday morning, the GFS is more progressive across the western High Plains and the amplified CMC and ECMWF are slower. At the surface, the 00Z UKMET has trended closer to the consensus with the surface low over the central Plains compared to its 12Z run. Taking these factors into account, a blend of the EC mean/GFS/UKMET should suffice for now. Pacific Northwest by midweek ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Deterministic model blend Confidence: Above average A strong storm system originating from the Gulf of Alaska is expected to begin approaching the Pacific Northwest coast by Wednesday morning after a period of quiet weather early in the week. Although the surface cold front is forecast to pass through the region mid-week, the parent surface low is expected to remain well to the north across western Canada. There are only minor model differences with the synoptic scale features at this time, so a blend of the deterministic guidance should work well. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Hamrick