Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 248 PM EDT Sat Apr 04 2020 Valid Apr 04/1200 UTC thru Apr 08/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: Less GFS blend after 07.00Z for western U.S. Confidence: Slightly above average 19Z update: With the rest of the 12Z guidance now available, there is not a large or significant difference with the system over the western U.S. to deviate from the previous blend preference. The GFS remains an eastern/faster solution where less of it should be used for day 3. Otherwise, a general model blend should suffice. ---previous discussion--- Shortwave energy moving through the northern Rockies will lift into southern Canada over the next 12-24 hours and with the large closed low dropping down the western U.S. coast, quasi-zonal flow is forecast to set up across the central/eastern U.S. through the next 3 days. A couple features of interest for the CONUS include the aforementioned western U.S. closed low. Through 07.00Z, the most recent model guidance shows favorable agreement as the low drops south off the California coast. After 07.00Z, some timing issues remain where the 12Z GFS remains a faster solution and is also centered further east, closer to the coast. The 12Z run did shift more favorably to the rest of the guidance such that more of its QPF (and mass fields) could be used in a blend (compared to its earlier runs which were considerably further inland and an outlier). Another feature is a northern stream shortwave that moves from British Columbia through the northern Rockies Monday into Tuesday. Despite some marginal timing issues (UKMET a bit fast, GFS/NAM slow), a general model blend should suffice for this area. Elsewhere across the CONUS, model differences are not significant enough to stray from a general model blend Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor