POTENTIAL MOISTURE PLUME INTO NORCAL NEXT WEEK

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THE BIG PICTURE

The major atmospheric models are coming into allignment on a potentially major wet period arriving across Northern California next week. Although this is still 5 days away, this amount of model agreement suggests we should take this trend seriously.

SHORT TERM

After sunny skies Friday and Saturday a small storm is still forecast brush Northern California Sunday into Monday. This will bring us only light showers.

THE BIG STORY

Tuesday may be mostly sunny, but out in the Pacific forecast models agree that low pressure will be diving south and directing a moisture plume toward Northern California and Southern Oregon.

This far out there is disagreement on the scope of this storm. The European model and its ensemble is the most aggressive, bringing a sizeable atmospheric river to the NorCal coast with heavy rain reaching the Bay Area and North Bay by midday Wednesday.

Right now the models agree on the general pattern, if not the timing and scope. Unlike the European, the GFS model currently keeps much of the action north of us, while the Canadian is in between the two.

In any case, if this pattern verifies, it could be a major rain maker for our region from Wednesday into next weekend. By Monday, the GFS is the driest model, and the European the wettest.

Here’s the current GFS. It focuses the moisture plume further north.

And the current European. Here the moisture plume is aimed squarely at NorCal.

This is still 5-10 days away so much may change.

That’s why in cases like this we look to the ensemble models, which average all possible outcomes to arrive at a consensus or “cluster.” And, yes, they all suggest that a significant wet period is likely from the Bay Area north, beginning Wednesday of next week.

It’s too early to get into specifics like rainfall amounts and precise timing. We’ll have more updates in the coming days.