Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 PM EDT Tue Jul 07 2020 Valid 12Z Fri Jul 10 2020 - 12Z Tue Jul 14 2020 ...Guidance/Predictability Assessment... The most notable concern in the medium range continues to be with smaller scale differences around an Eastern Seaboard coastal low currently being monitored by NHC. The latest 06z/12z runs of the GFS remain faster/more progressive with this low, while the UKMET remains the most developed (likely benefiting from a more offshore track over warmed waters). Today's blend from WPC leaned closer to the ECMWF which fit better within the overall ensemble low track spread as well. For later in the period, there continues to be above average consensus on reinforced troughing across the East and troughing moving into the Northwest. A composite blend of the ECMWF/GFS with the ensemble means seemed to provide a good starting point and good continuity with the previous forecast across the entire CONUS. ...Weather Pattern/Hazard Highlights... Upper trough energies will periodically work inland over an unsettled Northwestern U.S. and western Canada. A steady stream of ejecting impulses then progress downstream over southern Canada and the U.S. northern tier. This will force moderating fronts over the broad region and spawn some strong to severe thunderstorms. Convective rainfall potential may focus from the Midwest to the Northeast and with a stalled/wavy front over the humid South/Southeast. Triple digits maximum temperatures (approaching/exceeding some heat records) are likely from portions of CA and the Southwest/southern Great Basin to the south-central Plains, with heat indices making it feel closer to 115 in some places. A heavy rain/weather threat is also expected to lift from the coastal Mid-Atlantic to New England contingent on potential coastal low development and track. Santorelli/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