Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 147 PM EST Thu Nov 07 2019 Valid Nov 07/1200 UTC thru Nov 11/0000 UTC ..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... ...12Z Model Evaluation with Final Preferences and Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwaves cutting into the Pacific Northwest Ridge... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 07/00Z ECMWF Ensemble Mean and the 07/12Z NAM and ECMWF Confidence: Slightly Below Average The 12Z suite of numerical guidance continues to struggle in how the handle numerous and hard-to-time shortwave troughs riding around the periphery of an anomalously strong mid/upper level ridge over the Eastern North Pacific Ocean. The 07/12Z GFS has more energy, and therefore a stronger/faster frontal progression into the U.S. Pacific Northwest while the 07/12Z NAM and ECMWF clustered better together. Even though the CMC/UKMET were more aggressive than the ECMWF with the pattern, those models remainder closer to the NAM/ECMWF idea than they did with the GFS. No change in the preference based on the 12Z non-NCEP suite. ...Remainder of overall pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through Day 2, then less weight to GFS on Sunday Confidence: Slightly above average The start of the short range period shows broad troughing along the eastern 2/3 of the northern U.S., preceded upstream by anomalous ridging over the eastern Pacific into the Pacific Northwest. By Saturday/Sunday, the flow is expected to flatten a bit although another shortwave should send another arctic front into the northern U.S.. Except for the GFS being marginally stronger with the departing trough over the eastern U.S. on Saturday, the model agreement was generally good in terms of both position and intensity. However, shortwave energy dropping out of Canada late Saturday or early Sunday was stronger in the GFS than other global models which resulted in it having mass fields that were deeper/stronger from the Upper Midwest to Northern Rockies with correspondingly colder thermal fields. For that reason, think a general model blend works early on day 3...although increasingly less weight of the GFS should probably be used as during Day 3. One caveat is that cold air surging from Canada often times progresses southward faster than indicated by the models...which means the GFS idea can't be ruled out entirely. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Bann