Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 PM EDT Mon Sep 11 2017 Valid 00Z Tue Sep 12 2017 - 00Z Thu Sep 14 2017 ...Tropical Storm Irma will continue to weaken as it moves to the northwest and will bring heavy rain and severe weather... ...Heavy rain will continue to spread across the Southeast and Tennessee Valley... ...Showers and thunderstorms expected to increase across the western U.S... Tropical Storm Irma will continue to move farther inland in a north-northwesterly direction. It will move through the Southeast throughout Tuesday while weakening to a Tropical Depression, and will eventually lift north into the Tennessee Valley as a post-tropical cyclone by late Tuesday night/Wednesday morning and will approach the central Appalachians by Wednesday evening. As a result, heavy rainfall will persist across the Southeast through late Monday night. A high risk for flash flooding is possible through Tuesday morning for coastal South Carolina and eastern Georgia. In addition, there is a slight risk for severe weather in this region also. By Tuesday, heavy rain will continue for the western portions of the Southeast and Tennessee Valley, albeit not nearly as heavy precipitation. Meanwhile, precipitation will also begin to move into North Carolina and southern Virginia. There is a marginal risk for flash flooding throughout this area in addition to a marginal risk of severe weather across coastal North Carolina and a small part of coastal South Carolina. Expect light showers on Wednesday to occur in the Tennessee and Ohio Valley along with the Mid-Atlantic. For the most current information regarding Irma, including more information about wind and storm surge, please see the National Hurricane Center (www.hurricanes.gov). An upper level low off the California coast will slowly drift northward and stay nearly stationary through most of the short term period. This will bring moisture across the area and trigger isolated to scattered thunderstorms in northern and central California, the eastern Great Basin, the Southwest, and into the central Rockies. Most of this activity will be triggered by daytime heating--so expect highest coverage of convection during the afternoon/early evening. Some of these thunderstorms are capable of producing heavy downpours that could lead to flash flooding--so there is a marginal risk of flash flooding along the Sierra Nevada mountains and into the Great Basin. By Wednesday evening, the upper level low will move over the central California coast as it will become absorbed into the upper trough swinging across the Northwest. Thus, coverage of convection will increase through these regions in addition to parts of the northern Rockies. Expect some thunderstorms to also begin firing off along the Northern Plains by Wednesday afternoon. Reinhart Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php