Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 338 AM EDT Wed Jul 19 2017 Valid 12Z Wed Jul 19 2017 - 12Z Fri Jul 21 2017 ...There is a slight risk of severe thunderstorms over parts of the Upper Mississippi Valley/Northern Plains... ...Heavy rain possible over parts of the Upper Mississippi Valley... ...Temperatures will be 10 degrees above average over parts of the Central High Plains... A front extending from the Great Lakes roughly westward to the Middle Mississippi Valley then northwestward to the Northern High Plains will slowly move eastward off the Northeast Coast by Thursday evening while extending westward across the Northern Mid-Atlantic/Ohio Valley/Middle Mississippi Valley into the Northern Plains. Showers and thunderstorms will develop along and ahead of the boundary from the Great Lakes into the Middle Mississippi Valley and into the Northern/Central Plains that will advance eastward to the Northeast/Ohio Valley by Wednesday evening and off the Northeast Coast by Thursday morning. In addition, showers and thunderstorms over the Northern Plains, on Wednesday afternoon and evening, will move eastward to the Great Lakes/Ohio Valley by Thursday evening. Meanwhile, monsoonal moisture and daytime heating along with upper-level energy will aid in producing showers and thunderstorms over parts of the Southwest/Great Basin eastward into parts of the Central/Southern Rockies through Thursday evening. The showers and thunderstorms will have the greatest areal coverage from the late afternoon into the late evening on Wednesday and Thursday. Additionally, weak onshore flow off the Pacific will aid in producing rain along parts of the Pacific Northwest Coast starting overnight Wednesday and continuing into Thursday evening. Elsewhere, moisture rich air over parts of the Southern Mid-Atlantic/Southeast into the Gulf Coast State along with daytime heating and upper-level energy will aid in producing showers and thunderstorms over parts of the region through Thursday evening. The showers and thunderstorms will have the greatest areal coverage from the late afternoon into the late evening on Wednesday and Thursday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php