Bay Area residents can look forward to a gradual cooling trend throughout the week, according to the latest reports from the National Weather Service San Francisco. While the disturbance from the previous day, which resulted in isolated thunderstorms, has moved over Northwest California, a blanket of stratus is hugging the coast and has begun infiltrating some of the North Bay valleys in Sonoma and Marin counties. According to NWS San Francisco, "Once that occurs, look for sunny skies inland and for high temperatures to be a few degrees cooler than yesterday."
Sitting at about 1000-1500 feet overnight, the marine layer isn't expected to thicken significantly, allowing any formed stratus to retreat quickly to the coast. In the extended forecast, upper-level troughing to the east of the Pacific is set to move towards the Pacific Northwest, and temperatures are expected to continue their downward trend. The NWS states, "The weather should be relatively stagnant, with temperatures continuing the gradual cooling trend." These cooler conditions are predicted to prevail into the next week, as another trough may influence temperatures to drop a few degrees further.
Changes are minimal for the long-term outlook, spanning Thursday through Tuesday. The Bay Area will remain on the edge of upper-level troughing, potentially shifting to a quasi-zonal flow. The NWS foresees "Cloudy nights and coastal drizzle will be possible," due to a deepening marine layer reaching 1500-2000 feet by the end of the week. The weekend into early next week looks to maintain quiet and cool weather, with upper-level troughing nudging into the PacNW and perhaps far northern CA again.
Aviation-wise, the deeper marine layer is poised to enable farther inland stratus penetration. However, it'll take time for moisture to restore enough for stratus formation after drier air was mixed in yesterday. "Anticipating patchy stratus to fill in around the Bay Area by sunrise and linger into the late morning before mixing out to VFR," according to the NWS forecast for the aviation sector. For tonight, the return of the MVFR/IFR stratus seems likelier, as it combines a deep marine layer and restored moisture levels.
In marine news, moderate to brisk northwest breezes will persist through Friday, with strong northwesterly gusts leading to risky conditions for small craft on Wednesday, particularly across the outer waters and coastal jet regions. While moderate seas are expected through Friday, the odd choppy seas in the outer waters may occur.
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