Extended Forecast Discussion NWS Weather Prediction Center College Park MD 231 PM EDT Sat Mar 28 2020 Valid 12Z Tue Mar 31 2020 - 12Z Sat Apr 04 2020 ...Overview... Main player over North America next week will be an incredibly strong upper high moving east from the North Slope of Alaska through the Canadian archipelago. With 500mb heights likely above +3.5 sigma (and sea level pressure perhaps into the low 1060s mb which would be higher than records for all of April), this teleconnects to modestly zonal flow over the CONUS but mean/averaged troughing near both coasts. After a lead system departs the Southeast late Tuesday/early Wednesday, overall pattern will become drier and relatively cool for areas between the Rockies and Appalachians but mild for California into the Southwest. ...Guidance/Predictability Assessment... Model guidance has trended toward slightly better agreement in the medium range period compared to 24 hours ago across the lower 48 though forecast confidence remains average at best. The main uncertainty lies with the evolution of features from the eastern Pacific and Pacific Northwest early in the period, and as that moves toward the northern Plains, how progressive it is in the developing zonal flow. Both the GFS and ECMWF and their respective ensemble means are converging on an idea of an impressive high pressure over Canada dipping down however. The 00Z GFS was unusable with its signifcantly faster solution that was easily considered an outlier. The 06Z run was more in line with the ensemble mean and also closer to the non-NCEP guidance, therefore was incorporated more into the model blend. The latter portion of the medium range period, guidance diverged enough to warrant a heavy dose of the ECENS to maintain some continuity. ...Weather/Hazard Highlights... System moving out of the southern Appalachians Tue will spread modest rainfall and maybe some snowfall over the higher elevations into the Mid-Atlantic and Northeast Wed/Thu as it skirts the coast. In the West, precipitation will taper to lighter rain/snow showers as an upper low weakens over British Columbia. Temperatures will oscillate between cooler and milder than normal between the lead system and subsequent northern stream cold front later in the week. Larger area of cold temperatures will remain over Montana with some readings 15-20 deg below normal. Milder temperatures are expected over California into the Southwest. Fracasso/Taylor Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml