Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 318 AM EDT Mon Aug 12 2013 Valid 12Z Mon Aug 12 2013 - 12Z Wed Aug 14 2013 ...Heavy rain possible in the Southern Mississippi Valley... ...Noticeable cool-down for the Great Lakes ... The rather stagnant weather pattern over the US is about to become more protean... at least in the eastern half of the CONUS. The stationary boundary draped from the southern Plains into the Mid-Atlantic states should largely wash out today only to be reinforced by another surface boundary to its north. This next front should help induce abundant showers and thunderstorms along and ahead of it as it dips into the lower Mississippi Valley by early Tuesday. Afternoon and overnight convection could lead to flash flooding in some locations and WPC has highlighted areas from Eastern Kansas into northern Mississippi today and tomorrow... respectively... for a chance of excessive rainfall. To the north... another cold front should move through the Great Lakes today bringing in decidedly unsummer-like conditions to the northern states. Temperatures behind the front will be as much as 10-15 degrees below normal with overnight lows in the 30s possible Tuesday and Wednesday morning over northern MN/WI. This front will merge with the primary boundary to its east and south and then push offshore New England overnight Tuesday night. The southern portion will continue to sink southward into the Southeast but with less fanfare. In the west... WA/OR will finally dry out while precipitation focuses along and east of the continental divide along the stationary frontal boundary. Monsoonal moisture in NM/CO will keep a chance of thunderstorms in the forecast especially in the afternoon and early evening. Fracasso Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php