Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 356 AM EDT Tue Aug 09 2016 Valid 12Z Tue Aug 09 2016 - 12Z Thu Aug 11 2016 ...Severe thunderstorms and heavy rain possible across portions of the northern Plains... ...Heavy rain possible over the Eastern and Central Gulf Coast... ...Heavy rain possible over portions of Arizona and New Mexico... A stationary boundary draped from the Carolinas, across the Gulf states and into the southern Plains will weaken and diminish by tonight. However, tropical moisture pooled over the South and Southeast combined with a surface low near the central Gulf Coast will maintain scattered to widespread showers and thunderstorms from the Lower Mississippi valley/Gulf Coast up to the Mid-Atlantic region. Rainfall intensity will increase during the afternoon and evening hours, which will increase the risk for flash flooding, especially along the central and eastern Gulf of Mexico Coast. Showers and thunderstorms will also be possible from the Mid-Atlantic and further north through Wednesday as an upper-level impulse moves across the Ohio Valley into the Northern Appalachians. A front moving across the northern Plains and into the Upper Great Lakes will trigger showers and thunderstorms over much of the northern Plains through late tonight and early Wednesday. The showers and thunderstorms will expand eastward into the Upper Mississippi Valley/Upper Great Lakes and into the Northern High Plains into Wednesday. Some of the storms may become severe and produce periods of heavy rainfall. The Storm Prediction Center has issued a slight risk for the northern Plains. Additionally, onshore flow off the Pacific will produce rain over parts of the Pacific Northwest until the onshore flow ends by Wednesday morning. Monsoonal moisture and daytime heating will aid in producing showers and thunderstorms over parts of the Southwest/Eastern Great Basin into parts of the Central/Southern Rockies and High Plains through Wednesday. Localized heavy rain and flash flooding will be possible. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php