San Francisco International, CA

Weather Underground Forecast for Tuesday, June 18, 2013.

Wet and unsettled weather continues for parts of the East and South on Tuesday as a cold front dropping southeastward across the Midwest reinforces another frontal boundary extending from the Northeast through the Central Plains. Expect rain and thunderstorm activity along and ahead the advancing cold front in parts of the Ohio Valley into New England, while a cooler airmass behind this cold front leads to cooler daytimes highs in the Upper Great Lakes and Northeast. Areas of isolated to scattered showers and isolated thunderstorms are expected to develop south of the main frontal disturbance from the Mid-Atlantic and Southeast through the Central and Southern Plains. Impulses from from the West will enhance precipitation eastern Oklahoma and northeastern Texas, as well as create the potential for strong to severe thunderstorms in parts of the Central and Southern High Plains. The Storm Prediction Center issued a slight risk of severe thunderstorm development from the late afternoon through the evening. While the main concerns with these storms are isolated areas of hail and damaging wind gusts, a localized tornado threat remains possible.

Meanwhile, thunderstorm will pick up across the High Plains late Monday afternoon. The Storm Prediction Center has issued a slight risk of severe thunderstorm development for parts of the region. While the main concerns with these storms are hail and damaging wind gusts, conditions may turn favorable for isolated tornadoes by the evening.

Out West, an upper level low located off the Pacific Northwest coast will bring progressively better chances for showers to the region through the mid-week. The low will slowly work its way closer to the coast Tuesday, before moving inland Wednesday.