Bay Area baking in hot weather ahead of thunderstorms, increased fire risk from dry lightning
Above normal temperatures will be felt across the Bay Area for several days this week, with the hot weather giving way to increasing chances of thunderstorms and the possibility of lightning-sparked fires, forecasters said.
The National Weather Service said in its daily forecast discussion for the Bay Area that a ridge of high pressure is moving over Northern California on Monday. After the coastal fog and low clouds are peeled away, the region is expected to reach the mid-80s to upper 90s inland, with coastal areas in the 70s to low 80s.
There is no heat advisory Monday, although some inland areas will have a moderate heat risk for those spending extended periods of time outside. Tuesday is expected to be the warmest day of the week, with larger areas of moderate heat risk and some pockets of major heat risk. Forecasters were weighing whether to issue a heat advisory for Tuesday, with a decision expected later Monday.
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Overnight lows will be warmer than normal, with drier air limiting humidity recovery, especially in higher elevations, according to the Weather Service. The combination of warm nights and drying grasses and brush is expected to increase fire danger later this week, especially as moisture from Tropical Storm Mario moves in from Southern California beginning late Wednesday into Thursday.
The Weather Service said the incoming moisture will raise the chance of thunderstorms, especially across Monterey and southern San Benito counties, along with increased potential for dry lightning, which could spark new wildfires.
As of Monday morning, the best initial window for elevated dry thunderstorms appears to be after midnight early Thursday through late Thursday morning, primarily along the Central Coast region but moving farther north into Friday, the Weather Service said.
Rainfall totals are expected to be limited to a quarter of an inch for the few locations that receive it. Spotty showers may continue into Saturday, though forecasters say confidence in the pattern beyond the weekend remains low.