San Francisco International, CA

Weather Underground Forecast for Sunday, May 19, 2013.

Severe thunderstorm activity will persist for the Plains on Sunday as a broad low pressure system continues trekking through the region. The system will move from the Northern Plains and into the Great Lakes, creating two frontal boundaries. The warm front associated with this system will extend eastward over the Great Lakes and into the Northeast, kicking up scattered showers and thunderstorms into Sunday night. At the same time, a cold front extends southward from this system which will move off the Central Rockies and into the Central and Southern Plains. Counter-clockwise flow around this broad system will pull moisture and energy into the Plains from the Gulf of Mexico. This will support moderate to heavy showers and thunderstorms in between these two fronts. This system has a history of severe thunderstorm development across the Northern and Central Plains, thus, there is a moderate risk of severe thunderstorm development with large hail, damaging winds, and multiple tornadoes. These severe thunderstorms will most likely develop across central and eastern Oklahoma, through eastern Kansas, and into western Missouri. A slight risk of severe storm development remains in effect from northern Texas, through southern Minnesota and Wisconsin on Sunday. At the same time, the back side of this system will continue spreading moisture over the Intermountain West and Rockies. This will trigger more showers with isolated thunderstorms over the region through Sunday evening.

Meanwhile in the East, a trough of low pressure slowly moves over the East Coast and maintains shower and thunderstorm activity for the Mid-Atlantic states through the Northeast.