Rainfall Update ~ April 2017

Has 2016-17 Been Our Wettest Water Year?

The remarkable rain year continued through April!  The monitoring stations in the Napa County ALERT Rainfall Monitoring System added between 3 – 6 inches to annual rainfall totals, not quite double the long-term average for the month of April.  At the City of Napa Corp Yard, 46.06 inches have now been recorded for Water Year (WY) 2016-17.  Due to malfunctioning equipment, data are not currently available for the other extreme of the watershed, Mt. St. Helena, where we receive the most rainfall; however, the gauge that frequently gets the second-most rainfall, Mt. Veeder, has recorded 83.87 inches this year!  On average, the 17 rain gauges in the Valley indicate that we’ve received 179% of mean annual precipitation, further bolstering this water year’s position as the wettest in the 16-year ALERT System’s historical record.

We are currently experiencing an early heat wave in the beginning of May and it seems like the historic rainy season has come to an end, but the historical record tells us that we commonly receive only 95% of our rainfall by the end of April, with 3% falling during May.  In the City of Napa area, the month of May has only been completely dry in 5 of the past 30 years.  So, this means there may be even a little more rain to come!

The Napa State Hospital rain gauge has now logged 44.09 inches of rainfall, placing WY 2016-17 at the third wettest year since record keeping began in 1893.  In the number one spot is WY 1982-83 with a recorded total of 50.19 inches. 

– Paul Blank, Senior Hydrologist, paul@naparcd.org