Extended Forecast Discussion NWS Weather Prediction Center College Park MD 243 PM EDT Sat Apr 25 2020 Valid 12Z Tue Apr 28 2020 - 12Z Sat May 02 2020 ...Much above normal temperatures across the West pushing into the southern Plains by late next week... ...Stormy weather to progress across the central and then the eastern U.S.... ...Guidance/Predictability Assessment... Models/ensemble means continue to depict an amplified upper-level pattern that will slowly progress eastward across the U.S. mainland next week. A pronounced upper ridge over the West will be contrasted with an upper trough/closed low over the East where a moderately strong low pressure system is forecast. Models have been slowing down the eastward progression of this low with each new run as a deeper and more closed off upper vortex is forecast. The CMC is the most progressive piece of guidance while the GFS is slightly slower. The slowest guidance is the ECMWF/EC mean, and they are the preferred solutions after considering the overall high amplitude of the upper-level pattern together with the slowing trend indicated by all models. The WPC medium range pressure and fronts were derived from a 20% blend from the 06 UTC GEFS with 80% of the 00Z ECMWF ensemble means, combining with a small percentage of their deterministic solutions for Days 3 and 4. This composite solution further slows down the eastward progression of the low pressure system across the eastern U.S. compared with earlier forecast packages. ...Weather/Hazard Highlights... A building western U.S. upper ridge Tue into Thu will shift eastward over the central U.S. later next week. This amplified ridge will support much above normal temperatures to include a risk of record maximum/minimum temperature values from CA and the Southwest to south-central portions of the Great Basin/Rockies/Plains. Temperatures should moderate in the wake of the exiting upper ridge as Pacific system moisture/height falls work inland and promote some moderate precipitation mainly into the Northwest into later next week. The very warm air should be pushing into the southern Plains by late next week as the overall synoptic pattern slowly shifts to the east. Lead shortwave trough energies will meanwhile significantly dig over the central to eastern U.S. downstream of the amplifying western U.S. ridge. This will carve out an amplified mid-upper level trough/closed low and generate a deep surface low/frontal system that will rejuvenate as it tracks from the Plains/Midwest through the East Coast from mid to late next week. This developing system will increasingly tap Gulf moisture and instability to fuel an expanding area of rainfall together with strong to possibly severe thunderstorms. Enhanced precipitation will spread from the MS Valley/Midwest Tue through the Appalachians/Northeast Wed into Thu. Locally heavy rainfall/runoff issues are possible, mainly in recently saturated areas near the lower MS Valley/Mid-South Tue. 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