HERE IT COMES! NORTH BAY TIMING, RAINFALL AMOUNTS, IMPACTS

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Two storms, a small one and a big one, are bearing down on Northern California Thursday. By Sunday, the impacts of the pair of storms may include local flooding, steep rises on small streams and creeks, and dangerous driving conditions.

As of Thursday, both storms can be seen on the Pacific satellite loop. The first is just arriving along the coast of California. The second, bigger one can be seen upstream as a wave of moisture headed our way.

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Over the next 36 hours this wave feature will rapidly deepen and intensify around a low pressure center, becoming a potent storm for Saturday.

The arrival of the first storm will come Thursday around mid-afternoon, with the rapidly-intensifying second storm right behind. This first storm will clear out by early Friday, with some sun breaks possible Friday morning and afternoon.

Rainfall amounts from the first weaker storm look to range from about one third to three quarters of an inch across the North Bay.

In some ways it will seem like the rain doesn’t stop, as the second storm will barrel into the North Bay right on the heels of the first, arriving late Friday. This more intense storm will reach its peak in the early morning hours through early afternoon Saturday across the North Bay.

As the low intensifies off the coast, a strong jet stream will round the base of the low pressure trough, headed right into California.

This will help to draw in a lot of moisture from the southwest. The Western Center for Weather Extremes, which tracks atmospheric river events, shows the moisture flux into the Sonoma Coast for Saturday.

This will bring the storm into the weak to moderate AR range as it moves south along the California coast through the day on Saturday. Landfall along the Sonoma Coast may briefly spike moisture levels around midday to late afternoon Saturday.

Winds will be strong and gusty on Saturday, potentially reaching 40 mph in gusts, with higher winds in the hills and mountains.

Finally, this second stronger system should add around 2 inches or more to our total rainfall (storms 1 and 2) by Tuesday.

Here’s another look at potential rainfall totals by Tuesday.

In the Sierra, snowfall will be heavy and travel almost impossible from late Friday into Monday. The snow forecasting site Open Snow is predicting lots of new snow at ski areas over the next 5 days.

After Tuesday? Well, there are hints that another storm system may spin up off the Central California coast around the 15th, but early signs are it may stay too far west to impact us.

Overall, low pressure looks to continue to hang around the West Coast into the week before Christmas, with cold temperatures very likely to remain with us for the next 10 days or more.