Extended Forecast Discussion NWS Weather Prediction Center College Park MD 405 PM EDT Wed Jul 07 2021 Valid 12Z Sat Jul 10 2021 - 12Z Wed Jul 14 2021 ...Excessive Western Heat... ...Weekend Heavy Rainfall Threat for the Midwest/Mid-South... ...Pattern Overview with Weather Highlights/Hazards... The ongoing heat wave under the upper ridge will continue for the Great Basin to the Coastal Ranges and lower CO River Basin this weekend and into next week with temperatures 10-20F above normal each day with locally higher readings possible. Several daily temperature records are possible each day primarily over the western Great Basin through interior California to Arizona. Meanwhile, expect a heavy rainfall threat will emerge by the weekend for parts of the eastern Plains/Mississippi Valley and Midwest/Ohio Valley as fueled by return/pooling Gulf Moisture and instability along with lingering upper trough support and surface frontal system passages. Slow overall pattern/system translations and reinforcements suggest a threat for repeat/training cells that may offer a local runoff problem with main weekend focus over the Midwest/Mid-South. ...Guidance/Predictability Evaluation... Model and ensemble forecast spread in the wake of Elsa remains lower than normal over much of the lower 48 states through medium range time scales in a slowly evolving pattern with seemingly above normal predictability. The WPC medium range product suite was primarily derived from a blend of the 06 UTC GFS/GEFS, 00 UTC ECMWF/UKMET/Canadian and ECMWF/NAEFS ensembles along with the 13 UTC National Blend of Models. This broad composite tends to mitigate smaller scale guidance differences consistent with lingering uncertainties. The latest 12 UTC guidance overall remains in line with this scenario. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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 Hazards: - Heavy rain across portions of the Central and Southern Plains, Sat, Jul 10. - Heavy rain across portions of the Southern Plains and Lower Mississippi Valley, Sun, Jul 11. - Heavy rain across portions of the Upper Missouri Valley, the Middle Mississippi Valley, the Great Lakes, and the Ohio Valley, Sat-Sun, Jul 10-Jul 11. - Flooding possible across portions of the Southeast and the Southern Plains. - Flooding occurring or imminent across portions of the Middle Mississippi Valley and the Southern Plains. - Excessive heat across portions of northern California, southwestern Oregon, and the Desert Southwest, Sat-Mon, Jul 10-Jul 12. - Excessive heat across portions of southern California, the Southwest, the Great Basin, and the Interior Northwest, Sat-Wed, Jul 10-Jul 14. - Much above normal temperatures across portions of the Northern Rockies and Northern High Plains, Sun, Jul 11.