Extended Forecast Discussion NWS Weather Prediction Center College Park MD 236 AM EDT Fri Aug 02 2019 Valid 12Z Mon Aug 05 2019 - 12Z Fri Aug 09 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. Meanwhile upper ridging across the Four Corners region should gradually weaken. Models/ensembles showed relatively good agreement at the larger scales through the medium range, but did show some variability with respect to the details of specific systems. An upper low initially off the Pacific Northwest coast should begin to move inland by late next week, but solutions differ on the exact timing of this. Farther east, several shortwaves are expected to rotate through the broad cyclonic flow from the north central to the northeastern U.S. moving a couple cold fronts into the central/eastern states. Models show some differences on the timing and amplitude of these features. Given the general large scale agreement, a blend of the 12Z ECMWF/CMC/18Z GFS was used as a forecast starting point for days 3-4 (Mon-Tue), with a gradual transition to majority ensemble mean (ECENS and GEFS) weighting during days 5-7 (Wed-Fri). ...Weather Highlights/Threats... Monsoonal moisture will focus scattered showers and storms with locally heavy rainfall over the Four Corners 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 cold front. The Pacific Northwest will initially see high temperatures several degrees warmer than average Mon-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 Wed-Fri in the wake of the surface cold fronts, with high temperatures expected to be 5-10 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