HOPE (FOR RETURN OF RAIN) NOW APPEARING ON THE HORIZON

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As Northern California enjoys glorious February weather, the first hints of a pattern change back to wet are appearing on the horizon. The change is still 10 days away, but there is strong model consensus, for now, that rain may return in the last week of the month.

For now, high pressure is in charge across the NE Pacific, sending the storm track far north of California. (Images 1-2)

There will be very little change in this pattern for the next week. Any storms will pass to our east, and like the entire Western U.S., we should stay a bit cooler than normal for this time of year as cool continental air drops in from the north. (Image 3)

By February 23rd or so, signs of a change will be underway. The dominant high pressure center is forecast to retreat north and west toward Alaska, allowing low pressure to press toward the West Coast. (Image 4)

This should allow the storm track to be drawn south, following the base of the trough. The big question is how far west will the trough set up? Far enough west, and storms that spin up will approach California from the ocean, potentially bringing lots of moisture. Too far east, and they drop down over land, with very little moisture. The Euro ensemble model above shows a nice set up for a rainy scenerio.

How about the GFS ensemble? It’s similar, with an even better set up by the 25th. (Image 5)

By the 25th, the digging low pressure trough may pull the jet stream and storm track south, into California. (Image 6)

The long range models are already showing a healthy storm spinning up off the Northern California coast on the 25th. (Image 7)

The even better news is that both of the major ensemble models (which average lots of possible outcomes) show the same thing happening. Here is the European ensemble, showing rain and snow over California around the 25th. (Image 8)