Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 432 PM EDT Fri Jul 25 2014 Valid 00Z Sat Jul 26 2014 - 00Z Mon Jul 28 2014 ...Frontal system to bring the threat of flash flooding and severe weather to portions of the central and eastern U.S... ...Unseasonably cool air mass will move into the north central U.S. behind the cold front... A rather potent upper-level disturbance for mid-summer will dive into the northern plains from Canada on Saturday. Ahead of this upper-level disturbance, a surface low-pressure system will cross the Midwest on Saturday and reach the lower Great Lakes by Sunday. A portion of this frontal boundary will become slow-moving or stationary at times across the central U.S., and will serve as a focus for shower and thunderstorm development. Several areas of focused shower and thunderstorm development are possible tonight through the weekend. The majority of the thunderstorm activity will take place from the central Plains to the Midwest on Saturday and will shift eastward to the Lower Great Lakes and central Appalachians Saturday night into Sunday morning. Severe thunderstorms will be a possibility from the central Plains and Midwest/Ohio Valley on Saturday and extending eastward to the Mid-Atlantic on Sunday. For more information on the severe weather threat, please refer to the Convective Outlook products issued by the Storm Prediction Center. Flash flooding will also be a possibility Saturday night into Sunday across portions of the Ohio Valley and central Appalachians. Elsewhere, monsoonal moisture will continue to bring generally scattered showers and thunderstorms to much of the Southwest and portions of the central Rockies through the weekend. A moist and unstable air mass will also result in scattered showers and thunderstorms across the Gulf Coast states. Ahead of the cold front, temperatures will generally remain above average from the Southwest to the southern plains to the the Southeast. Behind the cold front, an unseasonably cool air mass will move in, with high temperatures on Sunday across the northern plains and Upper Midwest as much as 10 to 15 degrees below average. This unseasonably cool air mass is forecast to continue spreading southeastward behind the cold front beyond the short range forecast period. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php