Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 351 AM EDT Tue Jul 18 2017 Valid 12Z Tue Jul 18 2017 - 12Z Thu Jul 20 2017 ...There is a slight risk of severe thunderstorms over parts of the Northeast and the Upper/Middle Mississippi Valley... ...Heavy rain possible over parts of the Upper Midwest and Southern Florida... Moisture rich air will extend from the Southern Mid-Atlantic/Southeast and westward along the Gulf Coast through Wednesday into Thursday. Daytime heating and upper-level energy will aid in producing showers and thunderstorms across the region through Wednesday evening. The showers and thunderstorms will have the greatest areal coverage during the late afternoon into late evening on Tuesday and Wednesday. In addition, upper-level energy over the Northern Appalachians will move eastward out over the Western Atlantic overnight Tuesday. The energy will aid in developing showers and thunderstorms over parts of the Northeast into parts of the Northern Mid-Atlantic through Tuesday evening. Meanwhile, a front extending from the Upper Great Lakes/Upper Mississippi Valley to the Central Plains will move eastward to the Lower Great Lakes/Ohio Valley westward into parts of the Middle Mississippi Valley and Northern Plains by Wednesday evening. Showers and thunderstorms will develop along and ahead of the boundary from the Upper Great Lakes/Upper Mississippi Valley into parts of the Northern/Central Plains that will move eastward to the Lower Great Lakes and parts of the Ohio Valley by Wednesday evening. Additionally, upper-level energy moving onshore over Northern California will move northeastward to the Northern High Plains by Wednesday morning and to the Upper Mississippi Valley by Wednesday evening. The energy will aid in developing showers and thunderstorms over parts of the Northern High Plains on Wednesday morning that will move eastward to the Northern Plains by Wednesday evening. Elsewhere, monsoonal moisture, daytime heating, and upper-level energy will aid in producing showers and thunderstorms over parts of the Southwest/Great Basin and the Central/Southern Rockies through Wednesday evening. The showers and thunderstorms will have the greatest areal coverage during the late afternoon into late evening on Tuesday and Wednesday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php