RAIN RETURNS. CHRISTMAS EVE STORM LIKELY.

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BIG PICTURE

Over the next week or so the North Bay Area will be on the southern fringe of a series of storms sweeping into the Pacific Northwest. A few of these storms will give us a nice dose of rain, including a somewhat bigger, colder storm inbound for December 24th, Christmas Eve.

THE FIRST TWO STORMS

You can see the first storm and its low pressure center spinning up off the California-Oregon coast.

This storm will arrive around 5-6AM Saturday morning and will move through pretty quickly.

The rain should be over by late afternoon Saturday. We look to pick up about a half inch of rain from this system with up to a full inch in the coastal hills.

Storm number two will arrive quickly on the heels of the first, reaching us by Sunday evening. Again, it will move through quickly and weaken as it pushes south.

By Monday morning rain totals across the North Bay will be similar to the first storm, around a half inch, with more in the hills.

So, for the first two storms from Saturday through Sunday night, we will pick up around an inch or a bit more, with up to two inches in the hills of the North Bay.

CHRISTMAS EVE STORM

Looking ahead, a stronger, colder storm is forecast to reach the California coast late on Monday. This one will ramp up overnight into the early morning hours on Tuesday, Christmas Eve. We can expect periods of heavy rain, but once again the storm will move through quickly, clearing to showers by Tuesday afternoon.

This storm will be wetter, potentially dropping 1-2 inches of rain across the North Bay by late on Christmas Eve.

CHRISTMAS DAY AND BEYOND

Christmas Day should dawn beautiful and sunny. But by late in the day the first clouds from another storm system may arrive. At this point it looks like a continuing series of weak to moderate storms may arrive on or around the 26th, 27th and 29th.

You can see that the European model expects several waves of storm energy to be lined up in the Pacific to the west of California for Christmas Week, arriving every couple of days.

All of this is too far in the future to forecast exact times of arrival or rainfall totals for these systems, but it looks like we will continue to be on the southern edge of a zonal (straight, not meandering) storm track, one that is pushing storms directly east across the Pacific from Japan.

The ensemble forecasts have us on the southern edge of above average rainfall through Christmas Week. Much less rain is forecast to reach Central and Southern California where it remains very dry so far this season.

Finally, as the New Year begins, the ensemble outlooks hint that low pressure will retrograde to the west, with high pressure and drier weather returning to the Western U.S.

We’ll have more updates in the coming days!