Feb 19, 2017

Strong atmospheric river likely to bring widespread, perhaps severe flooding to Northern California on Monday

Sacramento, CA
USA
by
Daniel Swain
,
California Weather Blog

On the heels of a strong, damaging, and deadly Southern California storm on Friday, a new and powerful storm is bearing down upon Northern California.

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The atmospheric river associated with the Monday storm will be very impressive in its own right–the amount of atmospheric water vapor transport near the Interstate 80 corridor on Monday will be of a magnitude historically only seen every ten years or so in February. Even more problematic than the overall amount of moisture is that the atmospheric river boundary itself is expected to be very slow moving, and may in fact stall across some portion of Northern California.

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California is currently in the midst of one of its wettest winters on record, and precipitation since January 1st has already led to widespread water-related impacts. Widespread inundation of agricultural lands is occurring, which has begun to spread into low-lying nearby communities in the Central Valley; innumerably many mudslides and landslides have been occurring almost continuously in Northern California, causing numerous roadway failures and affecting some heavily traveled routes; and most of California’s major and minor reservoirs are now nearing capacity, requiring large water releases. All of this water is severely taxing California’s water storage, conveyance, and flood protection systems. With the major exception of the Oroville Dam spillway crisis–a situation that appears to have stabilized for the moment–no major failures have yet occurred elsewhere.

But given the magnitude of the incoming Monday storm and the precariousness of the present situation, it’s becoming increasingly likely that problems will arise this week. As others have pointed out, the present situation is very similar to those which have historically resulted in major levee failures in the Central Valley and Delta regions. Undoubtedly, this week’s weather will be a serious stress test for California’s aging water infrastructure. Indeed, the potential exists this week for severe flood-related impacts of a magnitude not seen in many years.