Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Thu Jul 19 2018 Valid 00Z Fri Jul 20 2018 - 00Z Sun Jul 22 2018 ...There is a slight risk of severe thunderstorms over parts of Central Plains and the Middle and Southern Mississippi Valley this afternoon and tonight... ...There is an enhanced risk of severe thunderstorms across the Ohio and Tennessee Valley on Friday... ...Heavy rain possible over the Upper Midewest this afternoon/tonight and parts of the Ohio Valley on Friday... ...Heavy rain possible over parts of the Southeast Coast and the Eastern Gulf Coast... ...Extreme Heat will continue across much of the south-central and western U.S.... A quasi-stationary front will remain in place across the Southeast through the end of the work week, before shifting northward as a warm front during the weekend. This will result in showers and thunderstorms along with a slight risk for excessive rainfall. A developing low pressure system currently moving into the Upper Mississippi Valley will continue to strengthen as it moves east-southeast over the coming days. This system will pull a large amount of warm, moist, and unstable air northwards from the Gulf of Mexico towards the low pressure center, becoming the epicenter for showers and potentially strong thunderstorms today and Friday. Best potential for heavy showers and strong thunderstorms will be to the east of the low pressure system as well as along it's associated frontal features. The Storm Prediction Center has outlined much of the Central Plains as well as the Middle and Southern Mississippi Valley as having a slight risk for severe storms this evening and overnight. As the system strengthens, they have outlined much of the Ohio and Tennessee Valleys as being in an enhanced risk for severe storms on Friday and Friday night. The Mid-Atlantic currently has a marginal risk for severe storms associated with this system for Saturday. Along with the strong storms, heavy rain will also be a concern. The Weather Prediction Center has outlined a portion of the Mid and Upper Missisippi Valley as being in a slight risk for seeing excessive rainfall. Portions of the Tennessee and southern Ohio Valley will have a slight risk for excessive rainfall during the day Friday. Meanwhile, monsoonal moisture and daytime heating will aid in producing showers and thunderstorms over parts of the Southwest/Great Basin and the Central/Southern Rockies through Friday evening, too. The showers and thunderstorms will have the greatest areal coverage during the late afternoon into the late evening on Thursday and Friday. Wix Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php