Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1246 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 NAM/GFS Evaluation with Preliminary 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/12Z ECMWF/12Z CMC (less weight by late Saturday) 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; though the CMC is weaker and does start to outpace the rest of the guidance later Saturday into Sunday. The middle of the road would support the deterministic 00Z GFS/12Z EC falling in line with both of their corresponding ensemble means while also keeping the 12Z CMC in through the fist half of Day 2. It should be noted that while the track of this system is in fairly good agreement with the blend of choice, the 12Z 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: Non-00Z NAM/12Z UKMET Blend 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. The 00Z GFS and 12Z ECMWF are reasonable outer bounds in terms of timing and amplitude and are in decent agreement with their ensemble means. The 12Z CMC is a nice middle ground between the GFS/EC. Therefore, this supports a blend of the 00Z GFS, 12Z EC and the 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 Pagano