Bay Area residents should prepare for various weather conditions over the next week, starting with warmer temperatures and transitioning to possible heavy precipitation and strong winds. In a heads-up alert, the National Weather Service San Francisco highlighted a "slight risk of heavy precipitation and slight risk of high winds" expected to impact the area from Thursday-Monday, December 12-16. While details are still forthcoming, the weather agency advises locals to stay updated as they solidify the forecast.
The outlook came amid a synopsis reported by NWS San Francisco, noting that the region's warm and dry conditions currently prevail. However, with the Rex Block pattern in place, characterized by high pressure over the Northern Great Basin and low pressure over the Desert Southwest, weather phenomena like haze and smoke from a prescribed burn east of Napa are expected due to stagnant conditions. A shortwave trough is also expected to bring cooler temperatures and mid-to-high-level clouds to the West Coast, which could result in patchy dense fog, particularly during the nighttime.
Looking ahead, Friday is projected to be the warmest day of the week, with clear skies and the continuing influence of the Rex Block. A transition is on the horizon, though, with a stronger shortwave trough anticipated to contribute to a change in the weather pattern. Coastal drizzle and increased onshore flow are on the cards, though precipitation probabilities remain below 40%, with no significant rainfall ("QPF") expected.
In aviation, the NWS has forecasted generally favorable conditions for flying, with VFR expected to dominate save for potential low ceilings and/or fog at locations like KSTS and KHAF. Winds should be light and variable during the mornings, shifting to onshore flows in the afternoons before easing off again at night. This pattern is set to repeat itself as the week progresses.
Marine conditions will also see changes, with longer-period swell and wave heights ranging from 3 to 7 feet persisting into the beginning of the weekend. By early next week, northwest winds are expected to intensify, leading to a rougher sea state with wave heights potentially reaching 14 feet offshore by Monday. As conditions evolve, NWS advises mariners and coastal residents to stay vigilant and keep abreast of the latest updates.
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