Weather Underground midday recap for Saturday, August 18, 2012.

Showers and thunderstorms moved up the West Coast on Saturday, while severe thunderstorm activity continued for the Southeast. Monsoonal moisture continued to advance northward from the Southwest on Saturday. This brought scattered showers and thunderstorms to California, the Great Basin, and into the Pacific Northwest and Intermountain West.

Additional moisture poured onshore from a low pressure system that lingered just off the West Coast. Most of the West Coast saw cooler conditions due to cloudy skies, while inland valleys remained hot from southern California through Idaho with highs reported in the mid-90s. Thunderstorm activity over the West also kept fire danger high due to prevailing warm and dry surface conditions.

In the East, a low pressure system in eastern Canada created a cold front that extended southward over the East Coast. This shoved offshore and into the Atlantic Ocean early on Saturday, which brought an end to showers and thunderstorms for most of the Northeast and Mid-Atlantic states. However, the tail end of this system extended westward through the Southeast and into the Southern Plains.

Ample moisture from the Gulf of Mexico allowed for some severe thunderstorms to develop along this frontal boundary. Strong and damaging winds were reported from the Lower Mississippi River Valley through the Southern Plains. Bloom, Kansas reported 75 mph wind gusts with dime size hail.

Behind this system, cooler air from Canada poured into the Northern Plains, Midwest, and Great Lakes. The region saw a few scattered showers and isolated thunderstorms as a weak cold front moved through the Upper Midwest. Temperatures in the Lower 48 states Saturday have ranged from a morning low of 30 degrees at West Yellowstone, Mont., to a midday high of 99 degrees at Corpus Christi, Texas.