Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1233 AM EDT Wed Mar 11 2020 Valid Mar 11/0000 UTC thru Mar 14/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed Low Affecting the Southwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A closed low off the California coast currently will slowly move eastward toward the southwest U.S., with several mid-level vorticity centers revolving around the common center of the low. Overall, the latest deterministic and ensemble guidance shows very similar large scale mass field depictions through the next 84 hours. The main differences are the orientation and axis of heavier QPF tied to the plume of atmospheric moisture. The ECMWF QPF is displaced further to the west (southern CA/NV), similar to the CMC and UKMET. While the GFS/NAM depicts higher amounts to the east over AZ. So while the mass fields are similar and a general model blend is preferred, there are some important differences noted in the QPF fields, particularly in the day 2/3 time frame. ...Northern stream trough tracking from the northern Rockies, Upper Midwest toward the Northeast through Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GFS/ECMWF blend Confidence: Slightly above average A lower amplitude longwave trough will track through the northern CONUS from Wednesday through Friday. At the surface, a cold front will steadily track to the east and south. The UKMET appears to be too fast with the trough progression while now, the 00Z NAM is on the slower end of the model spread. As the surface low deepens north of the Great Lakes, the NAM is displaced to the northwest further than the rest of the models while the CMC's depiction of the cold front is slower across Great Lakes / Mid-Atlantic region. For now, will favor a GFS/ECMWF blend which seems to be a consensus approach compared to the ensembles. ...Closed Low Developing Over Pacific NW Friday/Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM Confidence: Slightly above average Shortwave energy rounding the base of a ridge extending into the Gulf of Alaska is expected to quickly drop south/southeast along the western coast of North America, eventually evolving into a large closed low over the Pacific Northwest late in the week and this weekend. Overall the guidance is in reasonable shape for the mass fields, the exception being the 00Z NAM which is deeper and slower than the rest of the deterministic guidance. The 00Z GFS trended slower compared to its earlier runs and is a bit slower compared to the 12Z non-NCEP guidance. Based on the setup, this makes sense and the other guidance is likely to trend that way. For now, a non-NAM blend is preferred for this region. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor