Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 139 AM EST Sat Feb 15 2020 Valid Feb 15/0000 UTC thru Feb 18/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Final Model evaluation with preferences & confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ North-Central U.S. to the Northeast ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend, and less GFS after 60 hours Confidence: Above Average Broad cyclonic flow aloft will exist across the north-central U.S. this weekend after the departure of the strong cold front on Friday. A strong shortwave will cross the Dakotas and Upper Midwest on Saturday and then cross the Great Lakes on Saturday night, but given the paucity of moisture available, this should not be an impactful event. There is very little ensemble spread and the deterministic models are in very good agreement overall. The GFS gets slightly more amplified by Monday morning across southern Canada with the next shortwave perturbation to pivot around the larger parent low that is well to the north. There is similar agreement on the timing of the cold frontal passage. The 00Z ECMWF trended a little less amplified with the trough axis reaching the East Coast Monday morning. Trough building in across the Western U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/00Z ECMWF/12Z EC mean Confidence: Slightly above average Zonal flow that will initially be over the West Coast region is forecast to become more amplified by Sunday night as a shortwave trough tracks southeastward from the Gulf of Alaska. This will resulting in height falls across much of the western U.S. to begin the week. Differences with the 00Z NAM become apparent as early as 36 hours into the forecast period with a greater degree of amplification over British Columbia, and this becomes more apparent with the northern stream component over the northern Plains by Monday night. This in turns induces a stronger surface low over the Upper Midwest that has little support from the remaining guidance. The 00Z ECMWF trended slightly slower with the height falls across the Intermountain West on Monday compared to the 12Z run, and is faster with the northern stream trough over the Great Lakes by the end of the forecast period on Tuesday morning, with its surface low trending farther north over the northern Great Lakes. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick