California residents and southwestern United States motorists should be prepared for slippery travel over the passes while some thunderstorms associated with a storm system could be feisty, AccuWeather Meteorologists say. Disruptions to outdoor plans are likely, and travel may be slow in some cases due to the approaching storm. "An unusually cold storm will pivot slowly through California and the southwestern United States into the start of the weekend," AccuWeather Expert Senior Meteorologist K