Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 353 AM EDT Sun Sep 02 2018 Valid 12Z Sun Sep 02 2018 - 12Z Tue Sep 04 2018 ...Severe thunderstorms, heavy rain and flash flooding expected from portions of the Plains to the Upper Midwest... ...Widespread rain is expected for parts of the Southern Plains, Lower Mississippi Valley and Gulf Coast... A cold front will move through the Upper Mississippi Valley and Great Lakes region as a surface cyclone tracks east across northern Manitoba and Ontario. As the next frontal system forms east of the Rockies and moves out into the Central/Northern Plains this boundary will stall and then lift as a warm front by Monday night/Tuesday morning. This will keep much of the Plains/Upper Mississippi Valley/Upper Great Lakes in an active wet pattern. Strong to severe thunderstorms will likely develop today across portions of Kansas, Nebraska and Iowa -- where the Storm Prediction Center has issued a Slight Risk for severe weather. In addition, these storms will be capable of producing intense rainfall rates. Over the next couple of days a wide swath of areal averages of 2 to 4 inches of rain is forecast, with locally higher amounts. Slight risks of excessive rainfall/flash flooding are in effect, along with a Moderate Risk across Iowa and northwest Illinois. A few locations are already experiencing moderate to major river flooding across Iowa and Wisconsin. Any additional rainfall will exasperate the ongoing flooding. Scattered thunderstorms are expected to break out across portions of the Southwest over the next couple of days as upper-level disturbances encounter monsoonal moisture streaming into the region. Any of these storms could produce locally heavy rain. A plume of ample moisture will stream into the western and central Gulf Coast through Monday will help generate widespread rain and thunderstorms in the Lower Mississippi Valley and Gulf Coast. This moisture plume is forecast to shift westward, leading to widespread rain and storms by Labor Day in parts of the Southern Plains. Though conditions have generally been dry there, enough rain falling in one location could still cause localized flash flooding. Scattered showers and thunderstorms can be expected to fire across portions of the Southeast and the Northeast through the holiday weekend, with warm and humid conditions. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php