Extended Forecast Discussion NWS Weather Prediction Center College Park MD 220 PM EDT Sat Aug 08 2020 Valid 12Z Tue Aug 11 2020 - 12Z Sat Aug 15 2020 ...Overview and Guidance/Predictability Assessment... Models and ensembles reasonably agree 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 the Desert Southwest to the southern Plains. The WPC medium range product suite was primarily derived from a composite blend of well clustered guidance from the latest GFS/ECMWF, GEFS/ECMWF ensemble means and 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 Tue-Fri. The trailing front stalls 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 next week. Meanwhile, the Southeast/Florida will see diurnal convection of varying intensity. Within the broad area of shower/thunderstorm potential there will be some areas of heavy rainfall. Warm air surging northward ahead of the cold front is forecast to result in high temperatures soaring into the 90s on Tuesday across the interior Northeast. New daily high temperature records may be set at a few locations. Cooler air behind the cold front will gradually bring high temperatures down into the 80s for the rest of the week, but they are still warmer than normal. Meanwhile, triple-digit heat will continue over the southern High Plains and the Desert Southwest. In contrast, clouds and precipitation will keep afternoon readings cooler than normal for the central and southern U.S. A cool air mass behind a Pacific cold front will spread below normal temperatures across the Northwest into the northern Plains by next weekend. Schichtel/Kong 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