Extended Forecast Discussion NWS Weather Prediction Center College Park MD 109 AM EDT Wed Jul 22 2020 Valid 12Z Sat Jul 25 2020 - 12Z Wed Jul 29 2020 ...Western Gulf Coast to West-Central Texas excessive tropical rainfall/runoff threat... ...Overview and Weather/Hazard Highlights... The National Hurricane Center is monitoring an area of convection over the Gulf of Mexico that shows some potential for development as it moves westward during the short range. An expected track and deep moisture feed inland from the western Gulf Coast inland to west-central TX as the low dissipates will likely result in a threat for local excessive rainfall and runoff issues, with some areas across south central Texas forecast to see 2-3 inches of rain over the weekend (with locally higher amounts). 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 across the Upper Midwest on Sat, and a bit farther south, across the Central Plains Sun-Mon. 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 as relatively agreeable during the first half of the medium range, but consensus degraded later in the forecast period a bit more quickly than in recent days. A multi-model blend including the 12 UTC ECMWF/CMC and 18Z GFS was heavily used during days 3-4 (Sat-Sun), with a fairly rapid shift toward ensemble means after that, and a mostly ensemble mean-based forecast by days 6-7 (Tue-Wed). Deterministic guidance continued to struggle with shortwaves traversing the westerlies north of the ridge next week, and with the degree and timing of trough amplification, particularly across the Northeast U.S., downstream of the ridge. Ensemble means provided a bit more stability and consistency to the forecast by that time frame, and thus the emphasis placed on ensemble mean solutions by that time. Forecast confidence was average to slightly above average during days 3-4, and slightly below average by days 6-7. 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