Saturday, February 4, 2017

February Fights For Flooding Fame: New Atmospheric River Storm Approaching

I'm getting a funny sense of deja vu, like we've been here before. It's the fourth day of the month, and we are looking down the maw of a massive storm, a huge atmospheric river storm that threatens to cause flooding up and down the state of California. The difference is that it is the month of February, not January, and we've already had two sets of storms of historic proportions. And now another is coming. It feels like February is wanting to throw some weight around after the January show.
I've been wrapped up with a variety of housing projects, and hadn't been down to the Tuolumne River of late, but I stopped by yesterday and saw that flows are still in the 9,000 cubic feet per second range (this level is just short of official flood stage). The operators of Don Pedro Reservoir upstream are clearly trying to build up some storage space for the coming round of storms. This appears to be the case at a number of reservoirs around the state, as most are way ahead of normal, and have kept flows high. Of the major reservoirs in northern California, only Folsom (81%), Trinity (85%), and New Melones (73%) are below average, although New Melones is up 5 percent.

The snowpack is still very healthy, with a statewide average of 171% of normal for the date compared to 189% a week ago following a week of warmer conditions and little precipitation. The coming storm may once again be a warm one, raising concerns of some rapid snowmelt during the storm and possible flooding downstream.

Locally, the picture is also wet. My backyard rain gauge has gathered 15.16 inches so far, which is more than an inch higher than the average for the entire rain year since I've been measuring, starting in 1991 (my recorded average is 13.92" for 1991-2016). The official total for Modesto so far this year is 11.96", which is just short of the average rainfall for the entire year (12.16"). Modesto's records go back to 1888. The normal rainfall to date for Modesto is 6.98". It's been an interesting year, in that every single month since the start of the rainy season has been well above average. February may get to the average for the entire month by Wednesday. It's going to be an interesting week. Stay dry!

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