It turns out the big winner of Mother’s Day weekend was the marine layer.
An expected weekend warmup never really materialized, even across the interior and away from the water. Forecasts called for highs to climb steadily, peaking in the upper 80s and even lower 90s by Sunday across much of the region. Instead, most of the Bay Area stalled in the 60s and 70s all three days.
The setup was straightforward Friday and Saturday: persistent onshore flow kept the marine layer locked in across San Francisco, Oakland and the shoreline, largely as expected. But the twist came overnight Friday into Saturday, when the surface pressure gradient between the coast and the interior collapsed…