San Francisco International, CA

Weather Underground midday recap for Sunday, May 19, 2013.

Heavy rains and severe thunderstorm activity continued for the Plains on Sunday as a broad low trekked slowly across the Northern Plains. As the system progressed, counter-clockwise flow associated with the system pulled ample moisture and energy northward from the Gulf of Mexico, while an associated cold front reached southward from the system across the Central Plains. Forcing from the cold front combined with a dry line in the Southern Plains and the moisture laden conditions of the region allowed for multiple clusters of thunderstorms to continue from Saturday night through Sunday morning. Portions of eastern Kansas, western Missouri, and central/eastern Oklahoma remained at moderate risk of severe thunderstorm activity through the afternoon and evening as environmental conditions remained favorable for strong tornadoes, damaging wind gusts, and very large hail. Areas surrounding this moderate risk region from the parts of the Southern Plains into the Upper Mississippi Valley were at slight risk of severe thunderstorm development. While hail and damaging winds were the main threats of severe weather in these regions, a few tornadoes were also possible.

Meanwhile, heavy rains continued across the north-central U.S., while moderate to strong instability kicked up scattered thunderstorms and showers in the southeastern corner of the nation. Areas of eastern Montana through eastern Minnesota and parts of western Wisconsin remained under Flash Flood Watches and Warnings through the afternoon due to moderate to heavy rain and areas of rapid runoff. Flash Flood Warnings and various Flood Watches Warnings were also issued for parts of northern Georgia and eastern Alabama as intense rainfall amounts of 2 to 3 inches fell in one hour. In addition to heavy rain totals, hail and damaging wind gusts were possible with stronger storms in the southeastern corner of the nation.

Elsewhere, isolated to scattered showers and areas of thunderstorms developed across portions of the Mid-Atlantic and Northeast as a long warm front associated with this system reached across the Great Lakes into the Mid-Atlantic and humid conditions spread northward.