The San Francisco Bay Area is experiencing a cool down, with a slight chance of drizzle sweeping across the region. The San Francisco Bay Area National Weather Service has indicated that this unexpected shift is due to an upper-level system that will usher in cooler temperatures through Saturday. For a region that typically sees August as its second driest month annually, this sudden forecast of rain is somewhat of an anomaly.
The marine layer, that familiar blanket of coastal fog, normally delivers our grey summer mornings, but this weekend, we're looking to get actual precipitation from the skies. The cold front pushing through is expected "to bring a chance of light rain and/or drizzle to our forecast area" as it edges southward enough to influence our typical climate, the NWS Bay Area reported. Historically, places like Kentfield only record about 0.05 inches of rain in August, making the predicted conditions far from the norm.
On the technical side, forecasters are watching "a rare late August mid-latitude low pressure system," first spotted over the far northern parts of California. The cold air advection associated with this system is anticipated to cause not only the potential for precipitation but also a weakening of the marine layer's temperature inversion throughout the morning, according to the National Weather Service. Comfortably cool temperatures are expected as daytime highs drop a few degrees below normal along the coast and several degrees lower inland.
Mariners and aviators should be alert as the forecast includes a mixture of low stratus, mid-level rain clouds, and high cirrus, leading to challenging navigation conditions. The detailed update from the NWS mentions that despite adverse weather conditions, IFR conditions remain unlikely, but moderate onshore winds will likely increase during the afternoon hours. The forecast suggests an intricate dance between cooler air, atmospheric moisture, and the remnants of a summer trying to assert itself before the fall transition.
