Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 AM EDT Fri Apr 21 2017 Valid 12Z Fri Apr 21 2017 - 12Z Sun Apr 23 2017 ...There is a slight risk of severe thunderstorms over parts of the Southern Plains/Lower Mississippi Valley... ...Heavy rain possible from Oklahoma eastward to parts of the Central/Southern Appalachians... ...Heavy snow possible for parts of the BigHorn Mountains... There will be two main storm systems across the nation over the next couple of days -- one traversing across the northern Great Lakes and Northeast, and a second one developing over Texas and tracking towards the Southeast U.S. A frontal zone between these two surface lows will serve as a dividing line between above average temperatures across much of the eastern and southern U.S. through Friday, and below average temperatures from the central and northern plains to the Upper Midwest. With the northern surface low, scattered showers and thunderstorms are expected to fire along and ahead of the trailing cold front. The heaviest rainfall will likely develop over parts of upstate New York and extending eastward to New Hampshire. Lighter rainfall amounts are expected farther to the south across the Mid-Atlantic region. The southern Plains low pressure system will be stronger and have the potential to produce a few inches of rain from central Oklahoma to northern Arkansas. This same general area will also have a higher risk of getting severe thunderstorms through Friday as wind shear and higher instability create a favorable environment for these storms. This activity will move eastward towards the southeast states in time for the weekend. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php