Extended Forecast Discussion NWS Weather Prediction Center College Park MD 252 AM EDT Sat Aug 24 2019 Valid 12Z Tue Aug 27 2019 - 12Z Sat Aug 31 2019 ...Overall Weather Pattern... Broad cyclonic flow aloft is expected across the northern tier of the nation for much of the upcoming week as an upper level low develops over southern Canada and then Hudson Bay. This is expected to result in a broad upper level trough over the northern Plains and extending to the Great Lakes with a Canadian surface high in place. There will be multiple shortwave perturbations pivoting around this main low, and will result in reinforcing cold fronts crossing the central and northern plains. Upper level ridging extending from Texas to California is expected to continue through midweek, and also across the western Atlantic Ocean. ...Model Guidance Evaluation... Model agreement has improved with respect to the large upper low centered over Manitoba and Ontario on Tuesday, and the latest run of the UKMET has trended closer to the model consensus compared to its previous, more amplified run. By the end of the week, there is general agreement for a large scale trough centered over the Great Lakes region, with the CMC depicting the most amplified solution, and the 12Z ECMWF flatter with the trough axis. There has also been a trend for a stronger southwest U.S. upper ridge, with the ECMWF and CMC being the most amplified with this. By the end of the forecast period on Saturday, noteworthy timing differences exist with a shortwave crossing the Dakotas and also with a Pacific disturbance offshore, so the ensemble means provide a better starting point for Friday and Saturday. ...Expected Weather... A hint of fall is expected across the north-central U.S. next week with high temperatures generally 5 to 15 degrees below normal, which equates to high temperatures in the 60s and 70s F for much of this region. It should continue feeling like the middle of summer from Texas to the Great Basin and the Desert Southwest with temperatures 5 to 15 degrees above normal, with the greatest anomalies expected early in the week across western Texas and New Mexico. High temperatures could exceed 110 degrees across the lower elevations of southern Arizona and southeast California. Areas of moderate to locally heavy rainfall will be possible ahead of the cold front crossing the Upper Midwest and Great Lakes region early next week. For midweek and beyond, model uncertainty reduces confidence in placement of heaviest rainfall areas. However, there is the potential for a corridor of enhanced rainfall across the Central Plains later in the week. Hamrick 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 Hazards: - Heavy rain across portions of the south-central Plains into the Ozarks, and from the upper Midwest to the upper Great Lakes, Mon-Tue, Aug 26-Aug 27. - Heavy rain across portions of the central Plains, Fri, Aug 30. - Heavy rain along the Outer Banks of North Carolina, Mon, Aug 26. - Flooding occurring or imminent across portions of the Northern Plains. - Flooding likely across portions of the Northern Plains. - Excessive heat across portions of the interior valley of southern California, Mon-Wed, Aug 26-Aug 28. - Excessive heat across portions of the southern High Plains, Mon, Aug 26. - Much above normal temperatures across portions of western Oregon, Tue-Wed, Aug 27-Aug 28. 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