Extended Forecast Discussion NWS Weather Prediction Center College Park MD 209 AM EDT Sat Aug 03 2019 Valid 12Z Tue Aug 06 2019 - 12Z Sat Aug 10 2019 ...Overview and Guidance/Predictability Assessment... Upper ridging migrating slowly westward from the Gulf of Alaska to the Bering Sea through the forecast period favors troughing in the vicinity of the Pacific Northwest and downstream across the Great Lakes. A couple of cold fronts will sweep across the north central and northeastern U.S. during the forecast period along the base of the broad upper trough. Meanwhile upper ridging across the Four Corners region should gradually weaken and slide east toward the Southern Plains. Models/ensembles showed good agreement at the larger scales through the medium range, but did show some variability (perhaps slightly less than average) with respect to the details of specific systems. Given the general large scale agreement, a blend of the 12Z ECMWF/CMC/UKMET/18Z GFS was used as a forecast starting point with a slowly increasing percentage of ensemble mean (ECENS and GEFS) weighting during days 5-7 (Thu-Sat). ...Weather Highlights/Threats... Monsoonal moisture will focus scattered showers and storms with locally heavy rainfall over the Four Corners through much of next week as the upper high weakens. Elsewhere, rainfall will follow the front in the north but be more scattered and diurnally driven in the Southeast. Areas of more organized convection and heavy rain are possible across the central U.S. along the trailing end of the frontal boundaries in the central U.S. The Pacific Northwest will initially see high temperatures several degrees warmer than average Tue-Wed before a cooling trend arrives later in the week as the upper low begins to move inland. Relatively cool temperatures are also expected to move into the north central U.S. by late in the week in the wake of the surface cold fronts, with high temperatures expected to be around 5 deg F below average. 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