Extended Forecast Discussion NWS Weather Prediction Center College Park MD 212 AM EDT Sun Aug 04 2019 Valid 12Z Wed Aug 07 2019 - 12Z Sun Aug 11 2019 ...Overview and Guidance/Predictability Assessment... A slow-moving upper low initially off the West Coast is expected to move inland by next weekend. Downstream, an upper ridge initially centered across the Four Corners region is forecast to shift eastward into the Southern Plains. Meanwhile, broad cyclonic flow (traversed by a couple shortwaves and surface cold fronts) will persist from the Upper Midwest/Great Lakes to the Eastern Seaboard on the southern periphery of an upper low progressing across northeastern Canada. A blend of the 12Z ECMWF/CMC and 18Z GFS was used for the forecast during days 3-5 (Wed-Fri), with a shift toward majority ECENS and GEFS ensemble mean weighting during days 6-7 (Sat-Sun). The largest model differences were later in the period with respect to a shortwave crossing the Great Lakes/Northeast Sat-Sun, and with the system moving inland across the Pacific Northwest. With both of these features relatively high spread with respect to the details of timing/structure lended to favorability of ensemble mean solutions. ...Weather Highlights/Threats... The central U.S. will be the focus for areas of deeper convection through the forecast period, along the trailing end of a couple frontal boundaries that move into the Central/Southern Plains and then stall. Models show a signal for an area of heavy rainfall, perhaps associated with a couple rounds of intense convection from portions of the Central Plains into the Mid-Mississippi Valley Thu-Fri. Elsewhere, showers and thunderstorms should focus across the Northeast and portions of the Mid-Atlantic Wed-Thu along/ahead of a cold front. Farther west, monsoonal moisture will persist with diurnal showers and thunderstorms across portions of the Southwest and southern/central Rockies. Showers/storms may also begin to spread into the northern Great Basin/northern Rockies by next weekend as the Pacific upper trough moves inland. In terms of temperatures, expect hot conditions across the Southern Plains beneath the upper ridge, with high temperatures 5 to 10 deg F above average daily. Below average temperatures should spread into the Pacific Northwest by next weekend in association with the upper trough, with highs expected to reach 5 to 10 deg 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