Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 418 PM EDT Thu Apr 03 2014 Valid 00Z Fri Apr 04 2014 - 00Z Sun Apr 06 2014 ...Flash flooding possible through tonight across portions of MS/OH Valleys and central Appalachians... ...Severe thunderstorms possible through tonight from the southern Plains to the Ohio Valley and on Friday from the central Gulf Coast to the central Appalachians... ...Heavy snow possible tonight for portions of the Midwest and Upper Great Lakes... A very active spring weather pattern will continue across much of the contiguous U.S. through the Short Range forecast period. A vigorous upper-level disturbance is moving from the Rockies into the central U.S. this afternoon, with a surface low pressure system forecast to deepen as it moves from the central Plains into the Midwest tonight. Significant moisture and instability ahead of this system will result in widespread shower and thunderstorm development tonight from the southern Plains and Lower Mississippi Valley northward to the Ohio Valley. The Storm Prediction Center is forecasting a slight to moderate risk of severe thunderstorms for much of these regions. Please refer to the Convective Outlooks products issued by the Storm Prediction Center for further details on the severe weather threat associated with this system. Flash flooding will also pose a threat, particularly in an area from the middle Mississippi Valley eastward across the Ohio Valley, where deep moisture will lift across a west to east oriented stationary frontal boundary, resulting in the potential for multiple rounds of showers and thunderstorms with heavy rainfall. The system will shift eastward on Friday, with showers and thunderstorms spreading into the eastern U.S. Snow is forecast to fall on the north side of the low-pressure system, from the central/northern Plains and Midwest into the Upper Great Lakes. Heavy snowfall amounts of 6 to 12 inches will be possible for much of the Midwest and Upper Great Lakes tonight into Friday. Additionally, an area of mixed precipitation including sleet and freezing rain will be possible on the south edge of the snow area. Across the western U.S., a relatively weak Pacific storm system will move onshore this evening, bringing scattered rain and snow to much of the West into Friday, before another weak system approaches the region by Saturday morning, bringing more scattered showers and elevation snows to the region. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php