Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 344 AM EDT Thu Aug 16 2018 Valid 12Z Thu Aug 16 2018 - 12Z Sat Aug 18 2018 ...There is a slight risk of severe thunderstorms over parts of the Central/Southern Plains and the Middle/Lower Mississippi Valley... ...Heavy rain possible over parts of the Southern Ohio and Tennessee Valleys... A quasi-stationary front extending from the Northeast southwestward to the Southern Plains will have a wave of low pressure move from parts of the Upper Great Lakes/Western Ohio Valley to the Lower Great Lakes/Northern Appalachians by Friday evening. Showers and thunderstorms will develop along and near the boundary from the Lower Great Lakes southwestward to parts of the Southern Plains/Lower Mississippi Valley that will move eastward to the Northeast southwestward to parts of the Central Gulf Coast by Friday evening. In addition, upper-level energy over parts of the Northern/Central Plains will move eastward to the Lower Great Lakes by Friday evening. The system will produce showers and thunderstorms over parts of the Upper/Middle Mississippi Valley and parts of the Northern/Central Plains that will move eastward into the Great Lakes/Ohio Valley into parts of the Middle Mississippi Valley by Friday evening. Another area of upper-level energy over the Texas Panhandle will slowly move eastward to the Lower Mississippi Valley by Friday evening as well. The energy will aid in producing showers and thunderstorms over parts of the Southern High Plains that will likewise move eastward into the Lower/Middle Mississippi Valley by Friday evening into Saturday. Meanwhile, tropical moisture and weak upper-level impulses will aid in producing showers and thunderstorms over parts of the Southeast into the Central Gulf Coast through Friday evening. A third region of upper-level energy will move onshore over the Pacific Northwest on Thursday evening into Friday morning moving into parts of the Northern Intermountain Region by Friday evening. The energy will trigger showers and thunderstorms over parts of the Pacific Northwest into the Northern Intermountain Region overnight Thursday that will move into parts of the Northern Rockies by Friday evening. Elsewhere, weak monsoonal moisture and daytime heating will aid in producing showers and thunderstorms over parts of the Southwest/Great Basin and the Central/Southern Rockies through Friday evening. The showers and thunderstorms will have the greatest areal coverage during the late afternoon into the late evening on Thursday and Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php