Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1248 AM EDT Sun Aug 09 2020 Valid 12Z Wed Aug 12 2020 - 12Z Sun Aug 16 2020 ...Overview and Guidance/Predictability Assessment... Guidance still reasonably agrees that two main closed upper lows will track gradually eastward over Canada as trough energies along with temperature moderating and convection focusing fronts work across the northern half of the U.S.. Underneath, hot upper ridging will prevail over much of the nation's southern tier, with some record triple-digit maximum temperatures possible from interior CA to the Desert Southwest and the southern Plains. The WPC medium range product suite was primarily derived from a composite of best clustered guidance from the 12 UTC GFS/ECMWF, GEFS/ECMWF ensemble means and the 02 UTC National Blend of Models in a pattern with above normal predictability. WPC continuity is well maintained. ...Weather/Hazard Highlights... Wavy frontal passage will focus thunderstorms with some heavy downpours from the Midwest to the East Wed-Fri. The wavy trailing front nearly stalls from the Mid-Atlantic back to the north-central U.S. and impulses undercutting/ejecting from an emerging Northwest U.S. upper trough will fire episodes of strong thunderstorms from the north-central U.S. to the Mid-MS/OH Valleys this week. Meanwhile, the Southeast/Florida will continue to experience diurnal convection of varying intensity. Within the broad area of shower and thunderstorm potential there will be some areas of heavy rainfall contingent on less predictable flow details. 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