Weather models trending towards possible NorCal atmospheric river this weekend [View all]

This weekend = March 10-12. Excerpts below detail some pretty cool weather science.

San Francisco Chronicle / March 6, 2023

Wet low-pressure systems continue to chip away at the foundation of a high-pressure system just off the coast of California. Like a dam that’s full of leaks, the foundation of the high-pressure system will continue to fall apart as more rain and thunderstorms break through. If this keeps up, the high-pressure system could collapse by Friday, allowing a torrent of atmospheric moisture to flow into the Bay Area on the weekend.

The European, American and Canadian weather models are all suggesting that low-pressure systems will chip away at the Pacific High between Monday and Friday. This means that more rounds of rain showers and thunderstorms will make it onto the coast over the next few days, with isolated pockets of hail, damaging winds and lightning strikes all on tap for the Bay Area . By Thursday the weather models begin to suggest different outcomes for what will happen to the Pacific High. A couple scenarios keep it intact, meaning that only light showers and drizzles will be possible this weekend. But other scenarios suggest a complete collapse of the Pacific High, allowing an atmospheric river to rush toward Northern California.

Any low-pressure system that’s around to absorb all that moisture this weekend will evolve into a storm that could bring excessive rainfall to the Bay Area, Sacramento Valley, and Central Coast. The Sierra Nevada and peaks in Southern California would also get whacked again, on top of the historic snowpack that’s already sitting over the mountains.

For now, the weather models are still sifting through both scenarios. But with this winter already wetter than predicted by September’s long-range outlook, there is precedent for the advent of the wetter scenario, lining up with trends from the past few months.

LINK (paywall): https://www.sfchronicle.com/weather-forecast/article/atmospheric-river-bay-area-17821559.php