National Weather Force has issued a Thunderstorm Watch for the Sacramento Valley to San Francisco Bay area, effective now through this evening.
A group of thunderstorms will form on the northeast side of a compact upper-level low pressure system that is located just west, offshore of San Francisco. These storms will move from southeast to northwest along a line from Livermore to Concord at the center, east to Sacramento, but the entire area has the storms risk.
Lightning, hail, and gusty winds will all be likely with it as it moves through. In addition to this, the cold air aloft will bring funnel clouds through the area.