Extended Forecast Discussion NWS Weather Prediction Center College Park MD 101 AM EDT Tue Jul 21 2020 Valid 12Z Fri Jul 24 2020 - 12Z Tue Jul 28 2020 ...Overview and Weather/Hazard Highlights... An upper-level ridge is expected to intensify over the lower/mid-Mississippi Valley during the medium range. The ridge will promote another round of hot temperatures from the Northern Plains/Upper Midwest late this week into the weekend, reaching the Eastern Seaboard early next week, with high temperatures forecast to be 5 to 10 deg F above average. As is typical of such a pattern, the weather around the periphery will be active across a number of areas. Shortwave energy and associated surface frontal systems traversing mid/upper-level westerlies across the CONUS northern tier will result in the potential for showers and thunderstorms across several days from the Northern Plains/Upper Midwest east across the Great Lakes and the Northeast. The latest model guidance continues to show a signal for areas of heavy rain across the Northern Plains/Upper Midwest Fri-Sat and again on Sun-Mon. The southern Mid-Atlantic and portions of the Southeast will see scattered to numerous showers and storms Fri-Sat as a frontal boundary sags southward across those areas, before eventually retreating north as a warm front again. The central/western Gulf Coast will also see numerous showers and thunderstorms as a broad trough drifts westward across the Gulf of Mexico. Finally, the seasonal monsoon will be active across the Southwest/Four Corners regions late this week into the weekend, on the western side of the central U.S. ridge. Areas of heavy rain are possible. ...Guidance/Predictability Assessment... Model guidance as relatively agreeable during the first half of the medium range, but consensus degraded later in the forecast period a bit more quickly than in recent days. A blend of the 12Z ECMWF/18Z GFS was heavily used during days 3-4 (Fri-Sat), with a fairly rapid shift toward ensemble means after that, and an entirely ensemble mean-based forecast by days 6-7 (Mon-Tue). Deterministic guidance seemed to be struggling by the early next week with both the timing and intensity of shortwaves traversing the active westerlies across Canada and the U.S. northern tier, with solutions nearly out of phase with each other in some instances. Ensemble means provided a bit more stability and consistency to the forecast by that time frame, and thus the emphasis placed on ensemble mean solutions by that time frame. Forecast confidence was average to slightly above average during days 3-4, and below average by days 6-7. Ryan 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