The National Weather Service in San Francisco issued a synopsis early this morning, highlighting today's ongoing dry conditions and elevated fire weather concerns, particularly in the North Bay Mountains and East Bay Hills due to breezy offshore flow and lower humidity levels. Mount Diablo and Mount St. Helena recorded mid-30s mph wind gusts this morning, and despite a decrease in winds and a shift toward more onshore flow tonight, dry conditions are expected to persist until moisture increases over the weekend.
Regarding short-term weather, lighter offshore winds were noted this morning, with the highest gusts occurring at elevations above 1500 feet. Although the region's relative humidity has not reached critical levels, offshore winds are sitting at a -5.5 mb SFO-WMC gradient (negative indicating offshore-oriented), which is forecast to lessen throughout today, according to the NWS SF. Additionally, the forecast suggests the marine layer will deepen, and humidity will climb starting Friday, though substantial rain is not expected until the weekend.
An update from the NWS focusing on long-term weather prospects indicates an improving scenario, with ensemble guidance converging on a solution that could mean rainfall, especially from Sunday into Monday. Notably, northern regions of the Bay Area could see a tenth to half an inch of rain, with higher amounts along the coastal ranges, while the south may see less or no rainfall. Weather patterns are expected to continue into early November, though specifics regarding rain chances with future systems are still uncertain.
Meanwhile, the NWS Bay Area's social media post cautions residents about elevated fire weather conditions with breezy winds and low humidity, especially in the North Bay Mountains & East Bay Hills. An accompanying computer model visual depicts areas where breezy winds and low relative humidity overlap, signaling potential fire hazards. Increased vigilance in these areas is advised as light offshore flow transitions overnight.
⚠️Elevated Fire Weather Conditions tonight into Thursday. Offshore flow will develop tonight leading breezy winds & low humidity, especially the N Bay Mts & E Bay Hills. Here's a computer model showing where breezy winds and low RH overlap. #cawx #cafire pic.twitter.com/nK6B7PHrAz
— NWS Bay Area 🌉 (@NWSBayArea) October 24, 2024
Additionally, per NWS SF marine forecasts, the maritime community should prepare for breezy to gusty north and northwest winds through the weekend. Wave heights in outer waters are set to become moderate and then build beginning Friday afternoon, leading to significant waves of 10-12 feet expected by Monday. Lastly, a small craft advisory has been issued for specific coastal areas in response to the changing conditions.
