Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1158 AM EDT Wed Jul 03 2019 Valid 12Z Sat Jul 06 2019 - 12Z Wed Jul 10 2019 ...Overview and Guidance/Predictability Assessment... Moderately progressive flows will channel between a building/hot upper ridge over the U.S. southern tier and a mean upper trough near Hudson Bay. A series of convection focusing impulses/troughs will work over the U.S. northern tier. This will act to push a cold front southward over central and eastern U.S. This main front will provide stark contrast between refreshing post-frontal high pressure and an anomalously hot and humid warm sector. The trailing end of this frontal boundary is expected to stall from the Southern Plains to the Southeast, lingering into early next week before it begins to lift back northward as a warm front ahead of the next system. Southern stream impulses rotating around and lingering into the ridge will also provide a less certain local focus for convection/MCS activity into the hot sector. Meanwhile, shortwave energy diving south on the eastern periphery of the Alaska ridge is expected to reach the Pacific Northwest by the weekend, moving east to the northern Rockies by the early to middle portion of next week as it weakens. A multi-model blend including the ECMWF/GFS/UKMET/CMC was used as a forecast starting point during days 3-5 (Sat-Mon), transitioning increasingly to ensemble means days 6/7 amid growing forecast spread and run to run continuity variance. ...Weather Highlights/Threats... The frontal boundary crossing the central/eastern U.S. through much of the forecast period will focus areas of scattered to numerous showers and thunderstorms across a large area, including portions of the Plains, Ohio/Tennessee Valleys, and the Eastern Seaboard through the middle of next week. Models show a signal for areas of heavy rainfall along the immediate Southeast U.S. coastline from Sun into the middle of next week. A renewed threat of more widespread convection may develop across the Northern Plains and Upper Midwest by Mon-Tue as the next surface front and surface low move into the region ahead of the shortwave energy crossing the northern Rockies. High temperatures are expected to be 5 to 10 deg F above average across the Northeast on Sat ahead of the incoming cold front, but temperatures should decrease in the wake of the front to near seasonal norms starting on Sun. Meanwhile, a brief period below average temperatures is possible across the northern High Plains behind the front on Sat, before a return closer to normal on Sun. Finally, an area of relatively cool temperatures (highs 5 to 10 deg below average) may accompany the upper trough across the Northwest/Great Basin/northern Rockies during the early to middle portion of next week. Ryan/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