The Bay Area is girding itself as the National Weather Service in San Francisco has projected chilly mornings and mostly clear skies through the early part of next week. As the region braced for temperatures to plunge below freezing in several inland areas, a frost advisory, implemented for various zones, including CAZ502>504, 508, 510, 512, 513, 515, 528>530, remained in effect until this morning. For the uninitiated, the frost advisory flags an expectation of widespread frost, which could cause harm to sensitive vegetation and potentially unprotected outdoor plumbing.

A statement issued by the National Weather Service states, "After the sun comes up, the clear skies will allow temperature will begin to climb, but we'll only reach the mid-50s this afternoon for most populated areas." Despite the climb, higher terrain is not expected to shed the chill, remaining in the 40s. However, this prevailing cold snap is forecasted to shift dramatically come mid-week with the anticipated arrival of an atmospheric river, ushering in significant rain from Wednesday to Thursday.

Amid these conditions, the NWS Bay Area posted a Flood Advisory on social media that is in effect until noon PST today. This notice suggests minor flooding with potential interruptions to our day-to-day flow: "Flooding of highways, streets and underpasses." With rain expected Tuesday night through Friday morning, San Francisco and surrounding urban environments, as well as smaller streams, could struggle under the weight of urban runoff.

Flood Advisory Now in Effect until Noon Pst Today. #CAwx pic.twitter.com/LgRDf5a27O

— NWS Bay Area 🌉 (@NWSBayArea) February 8, 2025

The extended forecast from the NWS San Francisco indicates that "The heaviest period currently looks to be from late Wednesday through late Thursday, when 1-3" of rain is expected in the lowlands with more in the coastal mountains." While the actual low-pressure center will be further north than recent storms, the pressure gradient and wind potential are somewhat lower, and the rains may still trigger concerns, such as shallow landslides, if rain rates escalate, according to the USGS soil moisture sensors. The weather paradigm appears set to eventually dry out Friday before a dry weekend, although confidence in the clearing is moderate given the high levels of uncertainty this far out.

For mariners, strong northerly winds are expected to prevail through Tuesday, with bays relatively sheltered from the most intense gusts. The marine forecast, also from the NWS, indicates moderate to rough wave conditions that will continue over the next few days. Boaters and coastal communities are advised to stay alert as conditions evolve and more inclement weather is anticipated.