Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 357 AM EDT Fri Jul 20 2018 Valid 12Z Fri Jul 20 2018 - 12Z Sun Jul 22 2018 ...A moderate risk of severe thunderstorms is possible across the Tennessee and Ohio Valleys.... ...Heavy rain expected to impact the Ohio Valley and along the East Coast... ...Above normal temperatures to continue across the southern Plains along with the Pacific Northwest... A frontal system moving out of the Mississippi Valley will slowly move across the Tennessee and Ohio Valleys. Copious amounts of moisture will pool along the front along with unstable air. This will lead to more rounds of severe weather--particularly from northwest Tennessee into southern Indiana where the Storm Prediction Center has issued a moderate risk. Thunderstorms will span from the upper Great Lakes to the western portions of the Southeast--with flash flooding a concern across these regions. By Saturday, the system begins to push eastward toward the Northeast and Mid-Atlantic; precipitation will increase across the lower Great Lakes southward into Georgia and Alabama. There is a slight risk of severe weather possible along the southern Appalachians. A developing low off the Carolina coast will slowly move northward along the Mid-Atlantic and into the Northeast. Initially, the heavy rainfall will concentrate across the coastal portions of North and South Carolina today where a slight risk of flash flooding will be a concern. As the low moves toward the New England coastline by late Saturday night/early Sunday morning, heavy rainfall will impact this region where there is also a slight risk of flash flooding. Dangerous heat remains in place across the southern Plains, lower Mississippi Valley and into the Southeast/Tennessee Valley over the next few days where excessive heat warnings and heat advisories are in place. High temperatures will reach well over the century mark will occur across Texas and Oklahoma through this weekend. The Pacific Northwest will also continue to experience above normal temperatures--especially by the end of the weekend where temperatures could reach the mid to upper 90s. Elsewhere, monsoonal moisture will fire off thunderstorms across the Desert Southwest--where flash flooding could occur in favored terrain, desert regions, and urban corridors. A marginal risk of flash flooding is possible through Sunday. Reinhart Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php