Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 405 PM EDT Sun Apr 26 2015 Valid 00Z Mon Apr 27 2015 - 00Z Wed Apr 29 2015 ...Severe thunderstorms and flash flooding possible for portions of the southern plains and lower Mississippi valley and Gulf Coast... ...Temperatures be 10 to 20 degrees below average from parts of the Northeast westward to the central and southern plains and parts of the Rockies... A low pressure system will move across Texas this evening and tonight, arriving in the northern Gulf of Mexico by Monday morning. This low pressure system will bring widespread showers and thunderstorms to much of the southern plains tonight, reaching the western Gulf Coast by Monday morning. Showers and thunderstorms will continue to spread eastward across the Gulf Coast states into Tuesday as the low pressure system moves across the northern Gulf of Mexico. The Storm Prediction center is forecasting a risk of severe thunderstorms across portions of these regions through Monday. Please see the Convective Outlook products issued by the SPC for further details on the severe weather threat. In addition to the threat of severe weather, heavy rain and the possibility of flash flooding will exist over many of the same areas that will experience severe weather. A cooler air mass north of the low pressure system, along with clouds and occasional rain, will keep below average temperatures in place from portions of the Rockies east across portions of the plains. A persistent upper-level low will remain in place off the Northeast U.S. coast. This feature will keep below average temperatures and precipitation in place over the next couple days as a series of upper-level disturbances cross the Northeast. Scattered showers will be possible across much of the Northeast through Tuesday. Temperatures will be cold enough Monday morning for rain to mix with snow in some areas. An area of more widespread rain is possible Monday afternoon/evening along the New England coast. Areas of rain and snow showers will be possible across portions of the Rockies tonight into Monday as an upper-level trough crosses the region. A cold front will also bring the possibility of rain to portions of the northern plains through early Tuesday. Another Pacific frontal system will move into the Northwest early Tuesday, with rain possible again for this region. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php