Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 459 AM EDT Sat May 04 2013 Valid 12Z Sat May 04 2013 - 12Z Mon May 06 2013 ...Heavy rainfall with potential flooding will be possible over the Tennessee valley and Southern Appalachians... A cut-off upper low meandering from the Lower Mississippi valley to the Southeast will be the center of attention during the short range forecast period. Deep moisture getting pulled northward out of the eastern Gulf of Mexico and Atlantic will fuel moderate to heavy rains along a wrapped up cold front edging through the Tennessee valley and Southeast on Saturday. Early Sunday...the front will pivot northward and heavy precipitation will begin spreading into the southern Appalachians and southern Mid-Atlantic states. Some rumbles of thunder will be possible...but given the slow progression of the front and upslope flow against the Appalachians...flooding and flash flooding will be the primary threat with this system. Also...temperatures beneath the core of the closed low aloft could be low enough to support snow over southwestern Tennessee/northern Alabama late Saturday night. Elsewhere across the nation...a lingering frontal boundary will continue to produce some light rains over the Midwest and Upper Great Lakes this weekend. Upstream...a second cut-off upper low retrograding from the northern Great Basin to the California coast will trigger some widely scattered showers across the western U.S.. A lack of moisture will keep precipitation light and any snowfall will be confined to the higher elevations of the Rockies. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php