JANUARY UPDATE: GETTING RAIN THE HARD WAY BUT HINTS OF A CHANGE

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THE BIG PICTURE

California clears out for Thursday and Friday before another cold storm drops into the state from the north on Saturday. This storm will ride over the top of a big high pressure ridge to our west, dropping snow in the Sierra but mostly missing the Bay Area and North Bay.

SHORT TERM FORECAST

The last storm that dropped a half inch to over an inch of rain across the North Bay is clearing out. You can see the Sierra finally got a nice dusting of snow…up to 20 inches.

You can see the big high pressure ridge to the west that is blocking Pacific storms from reaching us directly. Instead they are riding over the top of the ridge and dropping into the Great Basin….and will for the next week at least.

By Saturday you can see the next storm riding over the top of the ridge, and reaching California.

We shouldn’t get too much rain here in the North Bay on Saturday. Mainly showers that will arrive in the late morning. A bit to the east the Sierra may get a decent snowfall, which will delight skiers and snowboarders.

After Saturday a big trough of low pressure looks to settle into the West for an extended stay. This will bring California some cold air, but it looks like any storms that reach us will drop down to our east, and only give us a glancing blow. That stubborn ridge of high pressure out in the Pacific will be the continuing culprit.

You can see the storm track pushed north, just brushing Northern California.

Because of this, through mid-January the ensemble forecasts show California may be drier than normal, as the storm track is sent north into the Pacific Northwest.

UBER LONG RANGE OUTLOOK

Around mid-January there are hints the storm track could change. Of course long range outlooks are quite unreliable, but there is model agreement. Here’s the scenerio.

The long range ensemble outlooks show a weakening of the high pressure ridge to our west, and a trough extending toward California starting around the 14th or 15th. This would be a better setup for getting rain, and more like a typical El Nino pattern.

This far out all we can do is look at the ensemble outlooks, which in the case of the European model average out around 100 different possible outcomes. It shows a gradual return of above normal rain to most of the state. This is the 7 day precipitation anomaly for January 12-19. The GFS ensemble is similar.

Of course this doesn’t guarantee anything, just shows trends. But after a relatively dry first half of January, we’ll be hopeful it verifies. You can see that this trend toward more moisture for California corresponds with the ensemble outlook for the jet stream.

Instead of riding over the top of the high pressure ridge, the ensemble guidance shows it aimed at California and even a bit to our south. Much more of a “typical” El Nino pattern where we have a strong southern extension of the jet stream.