Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Fri Apr 24 2020 Valid 12Z Mon Apr 27 2020 - 12Z Fri May 01 2020 ...Extended Period of Much Above Normal Temperatures Across the West... ...Stormy Weather to Affect the Central and Eastern States... ...Guidance/Predictability Assessment... The WPC medium range product suite was mainly composed from a blend of the 12 UTC ECMWF/ECMWF ensemble mean, the 18 UTC GEFS mean and the 01 UTC National Blend of Models Mon-Wed. The 12 UTC ECMWF offers a more amplified solution overall that seems a better fit with ensemble means than the less amplified 18 UTC GFS. The 00 UTC GFS/GEFS and ECMWF have since trended slightly more amplified, bolstering forecast confidence. Run-run continuity issues offer more uncertainty with subsequent flow amplitude later next week, so prefer a blend of more compatible ensemble means amid typically growing forecast spread. ...Weather/Hazard Highlights... A potent lead short range low/system will exit New England for the Canadian Maritimes Mon. The low offers some coastal/maritime threat, but will also support some lingering moderate precipitation back over the Northeast to include some snow over the cooled interior and elevated sections of New Eng. Early week shortwave passage far upstream should meanwhile bring a swath of modest precipitation across parts of the Pacific Northwest through northern Rockies. Guidance then strongly favors the building of a western U.S. mid-upper level ridge that should persist through the forecast period. This ridge will promote much above normal temperatures with the strongest upper ridging and greatest temperature anomalies likely to be through next midweek, with the hottest temperatures in the Desert Southwest where highs of 100-110F are expected. Early week energy ejection from the Northwest U.S. should subsequently dig/amplify over the central to eastern U.S. downstream of the amplifying western U.S, ridge. This should generate another organized surface low/frontal system that should intensify as it tracks from the Plains/Midwest through the East Coast mid-later next week. This developing system should produce an expanding area of meaningful rainfall, with enhanced precipitation expected to spread from the MS Valley/Midwest Tue through the Appalachians/Northeast Wed into Thu. As heavy rainfall is possible in some saturated areas around the lower MS Valley/Mid-South by Tue, flash flooding/excessive rainfall remains a concern. 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