Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1227 AM EDT Mon Apr 13 2020 Valid Apr 13/0000 UTC thru Apr 16/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Southern stream shortwave leading to intense surface low over Great Lakes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Deepening low pressure over the mid-MS to lower Great Lakes will swing an intense cold front through the eastern U.S. over the next 24-36 hours. The latest deterministic guidance shows very good agreement in the upper level pattern as well as the surface low track and depth. With the better consolidation in the mass fields in the day 1/2 time frame, a general model blend will be more than sufficient for this cycle. Amplifying upper trough over the northern U.S. through midweek ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 15.00Z; then non-GFS blend after Confidence: Average Reinforcing longwave troughing is expected over the northern U.S. through mid-week with multiple impulses pivoting through the flow. In this amplified pattern, the models show average to above average agreement in the large scale pattern with only minor speed/timing differences this cycle. The 00Z GFS is faster than the other deterministic guidance and also less amplified as the trough axis swings through the Intermountain West. With the other guidance in good agreement, a non-GFS blend after 15.00Z is preferred. Shortwave near the Pacific Northwest by midweek ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECENS/ECMWF and 18Z GEFS blend Confidence: Average A closed low over the North Pacific will round the periphery of an upper level ridge and then undercut toward the eastern Pacific into mid-week. Given the highly amplified pattern, there is increasing temporal and spatial differences that develop in the day 3 time frame. The GFS is on the faster envelope spread while the CMC is on the side. Given the spread and timing differences, a preference toward the ensembles remains a good approach. A blend of the 12Z ECENS/ECMWF and 18Z GEFS mean offer reasonable solutions at time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor