Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 433 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 Big Horn Mountains... A front extending from the Northeast southwestward to the Tennessee Valley then westward to the Southern High Plains will move eastward off the Northeast/Mid-Atlantic Coast by Saturday morning. A wave of low pressure over the Southern High Plains will move eastward along the boundary to parts of the Tennessee Valley and the Southeast by Saturday evening. The system will produce showers and thunderstorms from parts of the Mid-Atlantic/Northeast along and ahead of the front to the Southern/Central High Plains that will move of the Northeast/Northern Mid-Atlantic by Friday evening. As the wave of low pressure moves eastward out of the Southern High Plains by Friday evening, showers and thunderstorms will move eastward across parts of the Southern/Central Plains to the Tennessee Valley and the Central Gulf Coast by Saturday evening. In addition, showers and thunderstorms will extend from the Southern Mid-Atlantic westward to the wave of low pressure through Saturday evening. Furthermore, rain will develop over parts of the Northeast with snow over parts of Northern Maine through Saturday evening. Meanwhile, upper-level energy over the Northern/Central Rockies will move to parts of the Ohio Valley westward to parts of the Central/Southern Plains by Saturday into Sunday morning. The energy will aid in producing snow and lower elevation rain over parts of the Northern/Central Rockies that will start to wind down overnight Friday that will be restricted to parts of the Central Rockies by Saturday evening. Additionally, a front over Central Canada will move into parts of the Northern tier states overnight Friday into Saturday evening. The boundary will trigger rain over parts of the Northern Plains on Saturday morning that will move into parts of the Upper Mississippi Valley/Upper Great Lakes by Saturday into Sunday. Another front will move onshore over the Pacific Northwest into parts of California/Great Basin on Saturday morning into Sunday. Rain will develop over the Pacific Northwest/Northern California Coast and expand inland to parts of the Northern Intermountain Region on Saturday into Sunday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php