Extended Forecast Discussion NWS Weather Prediction Center College Park MD 234 PM EDT Sun Apr 26 2020 Valid 12Z Wed Apr 29 2020 - 12Z Sun May 03 2020 ...Much above normal temperatures spread from the West to the Plains middle to late this week... ...Stormy weather to progress across the eastern U.S. middle to late this week... ...Guidance/Predictability Assessment... Models and ensembles continue to depict an amplified upper-level pattern that will progress slowly eastward across the lower 48 midweek into next weekend. A pronounced upper ridge moving across the western U.S. into the Plains will be contrasted with an upper trough/closed low moving across the eastern U.S. where a moderately strong low pressure system is forecast. Model solutions have converged on a more common overall solution consistent with a previous trend toward a slower eastward progression of this low and deeper and more closed off upper vortex. Thereafter, there is a growing guidance signal for amplified eastern Pacific troughing to work more robustly toward the Pacific Northwest later next weekend. There could be a stronger embedded wave/cyclone swinging around the base of the trough toward the coast but uncertainty is too high to further determine the specifics. Accordingly, the WPC medium range product suite was primarily derived from a blend of reasonably well clustered guidance of the 06 UTC GFS/GEFS, 00 UTC ECMWF/ECMWF, together with a small portion of the 00 UTC NAEFS in a pattern with above average predictability. This composite solution maintains great WPC continuity and acts to mitigate the less certain smaller scale weather features and interactions. ...Weather/Hazard Highlights... An amplified western U.S. upper ridge midweek will shift eastward into the central U.S. later this week. This amplified ridge will support much above normal temperatures to include a risk of record maximum/minimum temperature values from the Southwest to south-central portions of the Great Basin/Rockies/Plains. Temperatures will moderate in the wake of the exiting upper ridge as Pacific system moisture/height falls work their way into the Northwest. This should promote mainly modest precipitation over the West, but could then support some organized weekend convection downstream over the north-central states. More robust energies/height falls upstream should work inland from the Pacific later next weekend and bring a good chance for enhanced precipitation across the Pacific Northwest and then the northern Rockies. Lead trough energies will meanwhile significantly dig over east-central U.S. downstream of the ridge. This will carve out an amplified mid-upper level trough/closed low and generate a well-organized surface low from the Great Lakes/OH Valley to the Northeast Wed into Fri. The main low and frontal system will sweep across the east-central to eastern U.S. and tap Gulf of Mexico and Atlantic moisture to fuel a swath of moderately heavy rainfall along with strong to possibly severe thunderstorms. Coastal low redevelopment may enhance Northeast rainfall and offshore maritime hazards into Fri before the entire system moves away into the Canadian Maritimes later next weekend. Meanwhile, chance of rain and scattered thunderstorms should increase from the central Plains eastward through the Ohio Valley into the central Appalachians next Sunday as a cold front approaches. Kong/Schichtel 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