Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 255 AM EDT Fri Mar 27 2020 Valid Mar 27/0000 UTC thru Mar 30/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level trough tracking from the West Coast to the Upper Midwest and into Quebec by Monday morning... ...Surface low moving from eastern CO into the Mid/Upper MS Valley and Ontario/Quebec... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/ECMWF/CMC (with slightly less weight by Sunday) Confidence: Slightly above average Models are coming into better agreement with respect to a mid-level trough tracking across the southwest into the midsection of the country Thursday into early Friday. However, the guidance starts to diverge once the mid-level wave becomes a closed low in the central Plains. The 00Z NAM is too progressive and farther north with both the mid level low and surface low. Conversely, the 12Z UKMET is too slow and thus the surface low lags behind. Meanwhile, the 00Z GFS/EC/CMC are in lockstep through much of this storm systems evolution. While the 12Z CMC was weaker and outpaced the rest of the guidance later Saturday into Sunday, the 00Z CMC is now in better agreement with the GFS/EC. Thus, the middle of the road would support the deterministic 00Z GFS/12Z EC falling in line with both of their corresponding ensemble means. It should be noted that while the track of this system is in fairly good agreement with the blend of choice, the 12Z/00Z EC may be a bit too strong within the 500mb/850mb levels which could impact thermal profiles. ...Shortwave trough and surface cold front approaching Pacific Northwest Saturday with the trough axis diving into the Southwest by Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/ECMWF Confidence: Average There remains some model differences with respect to a trough axis approaching the Pacific Northwest. Both the 00Z NAM and 12Z UKMET continue to be more progressive with the trough axis and shortwave energy moving into the Southwest by late Sunday; though a slight improvement was noted with the 00Z UKMET. The 00Z GFS/EC are reasonable outer bounds in terms of timing and amplitude (GFS a bit slower/ EC a bit more progressive and amplified) and are in decent agreement with their ensemble means. The 12Z CMC was a nice middle ground between the GFS/EC, though the 00Z CMC seems less amplified with the trough as compared to consensus. Therefore, the preferred model blend for this system is the 00Z GFS/EC. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Pagano