Extended Forecast Discussion NWS Weather Prediction Center College Park MD 645 PM EDT Wed Jul 22 2020 Valid 12Z Sat Jul 25 2020 - 12Z Wed Jul 29 2020 ...Western Gulf Coast to South-Central Texas Heavy Tropical Rainfall/Runoff Threat... ...Overview and Weather/Hazard Highlights... The National Hurricane Center is still monitoring a low and areas of convection over the southeastern Gulf of Mexico that continue to show potential for development during the short range. An expected track and deep moisture feed inland from the western Gulf Coast inland to south-central TX as the low dissipates will likely result in a threat for local heavy rainfall and runoff issues, with some areas across south-central Texas forecast to see widespread 2-3 inches of rain this weekend, with locally higher amounts possibly enhanced especially over Texas Hill Country terrain. An upper-level ridge will intensify across the south central U.S., promoting more hot temperatures over an expansive area of the nation. Highest anomalies may stretch from the North-Central Plains/Upper Midwest to the Eastern Seaboard into early next week, with high temperatures forecast to be 5 to 10+ deg F above average. As is typical of such a pattern, the weather around the periphery of the ridge will be active across a number of areas. Flow will tend to amplify both east and west of the ridge, with ensembles favoring troughing near/off the West Coast, and also across the Northeast by the early to middle part of next week. Shortwave energy and associated surface frontal systems traversing mid/upper-level westerlies across the CONUS northern tier will result in the potential for showers and thunderstorms across the Northern Plains/Upper Midwest east across the Great Lakes and the Northeast Sat-Mon. A cold front is forecast to gradually sag southward and eventually becoming stationary from the Central Plains to the Ohio Valley, where it will continue to focus showers and thunderstorms into the middle of next week. The latest model guidance continues to show a signal for areas of heavy rain over the Upper Midwest on Sat, and a bit farther south across the Central Plains Sun-Mon and onward. Finally, the seasonal monsoon will be active across the Southwest/Four Corners regions late this weekend, on the western side of the central U.S. ridge. Areas of heavy rain are possible, and any tropical surge over TX toward the southern High Plains/Rockies by early next week may add additional moisture across the Southwest. ...Guidance/Predictability Assessment... Model guidance is relatively agreeable during the first half of the medium range, but forecast spread increases days 6/7. A multi-model blend of the compatible 06 UTC GFS and 00 UTC ECMWF/CMC/UKMET was used during days 3-5 (Sat-Mon), with a fairly rapid shift toward the still reasonably compatible 06 UTC GEFS mean and 00 UTC ECMWF ensemble mean days 6-7 (Tue-Wed). This guidance was also blended with the 13 UTC NBM. Schichtel/Ryan Hazards: - Heavy rain across portions of the Central Plains, the Central Rockies, the Lower Mississippi Valley, the Central Great Basin, the Southern Rockies, the Northeast, the Southeast, the Central Appalachians, the Southern Plains, the Ohio Valley, and the Southwest, Mon-Tue, Jul 27-Jul 28. - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Northern Plains, the Upper Mississippi Valley, the Southern Plains, and the Southwest, Sat-Sun, Jul 25-Jul 26. - Heavy rain across portions of the Central Plains, the Northeast, the Northern Plains, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Upper Mississippi Valley, the Southeast, and the Southern Plains, Wed, Jul 29. - Flooding occurring or imminent across portions of the Central Plains and the Northern Plains. - Excessive heat across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Sun, Jul 26. - Excessive heat across portions of the Central Plains, the Upper Mississippi Valley, and the Northern Plains, Sat, Jul 25. - Excessive heat across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, and the Ohio Valley, Mon, Jul 27. - Excessive heat across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southeast, and the Ohio Valley, Mon-Tue, Jul 27-Jul 28. - Much above normal temperatures across portions of the Central Plains, the Middle Mississippi Valley, the Great Lakes, the Upper Mississippi Valley, and the Northern Plains, Sat-Sun, Jul 25-Jul 26. - Much above normal temperatures across portions of the Great Lakes, the Mid-Atlantic, the Northeast, and the Central Appalachians, Mon-Tue, Jul 27-Jul 28. - Much above normal temperatures across portions of the Great Lakes, Sat-Mon, Jul 25-Jul 27. 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