Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 234 AM EDT Thu Jul 17 2014 Valid 12Z Thu Jul 17 2014 - 12Z Sat Jul 19 2014 ...Heavy rainfall likely for parts of the Southern Plains and Lower Mississippi Valley... ...Comfortable temperatures and low humidity still on tap for the Midwest and eastern US although there will be an increased chance for showers along the Appalachians on Friday into Saturday... ...After todays brutal heat across eastern Washington and Oregon...a slow cooling trend is likely over the next few days... A slow moving upper level disturbance will interact with a surprisingly significant front over the Southern Plains with moisture feeding northward from the Gulf of Mexico to generate moderate to heavy rainfall and threat of flooding from northern Texas across Oklahoma and Arkansas over the next several days. North of the frontal boundary...rain will combine with unseasonably cool temperatures while south of the front...heavy rainfall will occur as slow moving heavy thunderstorms will likely form each day. A persistent area of high pressure and cooler and drier air has now reached much of the eastern US and will continue to influence the weather over the region for the next several days. While a low pressure system over the Southern Plains is responsible for the heavy rainfall there...moisture will begin to creep eastward across the Lower Mississippi Valley on Friday and begin to move north and eastward into the Tennessee Valleys and Appalachians on Saturday...with an increasing chance of showers. However...temperatures will continue to be quite moderate across much of the East through the next several days...except the Gulf Coast and Florida. The extreme heat experienced today along the Washington/Oregon border will diminish over the next few days although the long term still shows the potential for a rather intense surge of heat next week over much of the West. Scattered afternoon and evening thundershowers will continue to affect parts of the Far West for the next few days. Kocin Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php