Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 149 AM EST Mon Nov 18 2019 Valid Nov 18/0000 UTC thru Nov 21/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Less weight on the 00Z GFS after 20.12Z Confidence: Average ---06Z UPDATE--- The 00Z CMC has trended closer to the other models with the shortwave digging into the Great Lakes later in the period, so it could be incorporated into a model blend. The 00Z GFS still seems to be spreading height falls out of the Southwest too fast compared to the remainder of new 00Z model runs. One other notable model difference has developed near the U.S.-Canada border with some disagreement on the latitude of a shortwave that will be getting sheared out over the Northern Rockies. This leads to disagreement in the placement of a swath of QPF. A compromise is preferred at this point. ---PREVIOUS DISCUSSION--- For the next several days, models are in reasonably good agreement with the synoptic pattern, and the general placement and magnitude of QPF. Some of the more substantial spread by mid-week will be related to typical timing bias, as the 00Z GFS and ensemble members are faster with pulling the closed upper low out of the Southwest, while the 12Z ECMWF and ensemble members are slower. Given the strength of the upper level low, and a ridge building over the top of it in the Pacific Northwest, the preference is to lean on the slower side of the model spread, with less weight on the 00Z GFS by Wednesday. There is also some timing spread with a shortwave digging from Canada into the Great Lakes. In this case, the fastest model is the 12Z CMC, with most of the other deterministic models slower and in better agreement. The preference is to lean toward model consensus for this wave, with less weight on the 12Z CMC by Wednesday as well. Thus, the overall model preference could be characterized by a general model blend, shifting toward greater weight on the 12Z ECMWF, 12Z UKMET, and 00Z NAM by Wednesday, and less weight on the 00Z GFS and 12Z CMC. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers