Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 132 PM EST Mon Dec 02 2019 Valid Dec 02/1200 UTC thru Dec 06/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average 19Z update: No significant changes to the model preference with the rest of the 12Z guidance now available. There still is reasonable agreement with the shortwave troughs over the northern tier and Northeast U.S. and with the approaching storm system for southern California and the Southwest U.S. by mid to late week. Anomalously deep upper trough over the Mid-Atlantic and Northeast U.S. is well agreed upon with the latest model guidance through the next 24 to 36 hours and any model differences remain on the smaller scale and likely driven by mesoscale processes. Other notable features of interest in the next 3 days include another shortwave trough moving through the northern Plains and Great Lakes through Tuesday that will reinforce the large scale troughing over the eastern U.S. through mid-week. Here, models are in fairly good agreement though the 12Z GFS is a bit flatter with the shortwaves by Thursday and therefore faster than the rest of the guidance. The ECMWF/CMC are on the slower side of the guidance envelope while the UKMET and the NAM to some degree offer a compromise solution. Out west, a closed low off the northern California coast will drop southward and then move inland by 48-60 hours across southern California. Through 60 hours, there is fairly good agreement with the large scale setup though between 60-84 hours as the wave ejects into the southern/central Plains, the UKMET is considerably slower. The GFS/NAM offer a more amplified solution with the shortwave and the ECMWF would be a good consensus approach at this time. Another significant west coast system will begin to approach the west coast by the end of the forecast period /Thursday night/ and at this point, model guidance is in fairly good agreement. Given the relative good model agreements (outside typical model biases seen), a general model blend would suffice for the large scale mass fields. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor