Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 206 PM EDT Sat May 20 2017 Valid 00Z Sun May 21 2017 - 00Z Tue May 23 2017 ...Severe thunderstorms possible from portions of the southern plains to the Ohio valley... ...Heavy rain possible from portions of the southern plains and Mississippi valley to the Appalachians... ...Significant warming trend expected for the West Coast states... A low pressure system is expected to gradually deepen as it moves across the Midwest tonight and into the upper Great Lakes on Sunday, and Ontario by Monday. The trailing cold front associated with the system will produce numerous showers and thunderstorms tonight from the Gulf Coast states to the Upper Midwest. Some thunderstorms could be severe, and the Storm Prediction Center is forecasting a slight risk of severe thunderstorms from portions of Texas to the Ohio valley. Heavy rain is also possible, with localized flash flooding. Sunday and Sunday night, the front will move east, with numerous showers and storms expected once again along much of the Gulf Coast and north to the lower Great Lakes and along most of the East Coast. Heavy rain and isolated flash flooding will be possible once again. The southern portions of the front is expected to become stationary across Texas, and severe thunderstorms are possible across this area once again on Sunday. Showers and thunderstorms are expected to persist into much of Monday along the East Coast as the front will not move offshore until Monday night. The stationary portion of the frontal boundary will persist from Texas to the Gulf Coast through Monday, with numerous showers and thunderstorms and potentially heavy rainfall expected to persist. A secondary frontal boundary is forecast to develop late Sunday and Monday from the northern/central plains to the Midwest, bringing another round of scattered showers and thunderstorms to those areas. High pressure aloft is expected to strengthen along the West Coast through early next week, resulting in dry conditions and rapidly warming temperatures. High temperatures on Sunday will rise will into the 80s and 90s for much of the interior West Coast states, but 90s will become much more widespread by Monday, with some areas of interior California approaching 100. These temperatures will be 10 to 20 degrees above average for many areas. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php