A hotter finish to the weekend is in store with inland temps soaring into the 90s for Sunday. We ll also see a Spare the Air day with unhealthy ground level ozone levels in the East Bay valleys. By the evening out attention turns to increasing dry lightning potential which has activated a Red Flag Warning for higher elevations throughout the Bay Area into Tuesday night. Mid-level moisture will begin increasing Sunday night as atmospheric lift begins to increase around the same time. Even without the added convective boost of daytime heating, this overnight scenario will be unstable enough to fire up a chance for night time thundershowers, occurring above a shallow layer of drier air below. While some lightning may be accompanied by some rain, it may not be enough in some instances to extinguish fires sparked by lightning which is the prime cause for our Red Flag Warning over the next few days instead of the more typical combo of hot temps and dry gusty winds. Moisture should increase into Tuesday that will allow for a better potential for showers across some of the lower elevations which may hopefully suppress fire danger as thundershowers will have a greater chance for wetting rain with lightning strikes. As of now, its looking like the North Bay hills will see the highest chance for thundershowers for the next few afternoons but isolated showers and brief thunder will be possible across the rest of the Bay Area at least until early Wednesday.Temps should stay hot inland into Monday, then trend cooler by midweek as the upper level low responsible for the thunder component of the forecast begins to lift to the east. Rob Mayeda (Published Sunday, Aug. 18, 2013)
A chance of dry lightning hitting the Bay Area today and Monday has prompted the National Weather Service to issue a red flag warning for fire danger, a forecaster said.
The low-pressure front moving into the region as early as this afternoon brings a chance of showers, isolated thunderstorms and dry lightning through Tuesday, National Weather Service forecaster Bob Benjamin said.
Lightning strikes combined with extremely dry conditions across inland hills and valleys could bring significant fire danger, prompting the red flag warning for counties in the North and East Bay across San Mateo County to the Santa Cruz Mountains, Benjamin said.
Though there is a 20 to 30 percent chance of rain accompanying the front, there is "little chance of rain ever hitting the surface," Benjamin said.
Cal Fire has said additional firefighters will be placed on duty during the heightened fire danger.
The red flag warning goes into effect at midnight tonight and will remain in effect until noon on Tuesday.
Published at 2:29 PM PDT on Aug 18, 2013
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