Storm Data and Unusual Weather Phenomena - CIG

OUTSTANDING STORMS OF THE MONTH1. SEVERE FLOODING IN NORTHWEST CAUSES EXTENSIVE DAMAGEThe first month of 1997 was not a good one for western Nevada and east-central California. Excessiveamounts of rainfall coupled with the melting of the deep snowpack in the Sierra Nevada Mountains, causedmany rivers and their tributaries to flow out of their banks. A winter storm in late December depositedup to 8 feet of snow at the higher elevations and up to three feet in the valleys (See December 1996 issueof Storm Data). A 968 mb (28.59" Hg) low pressure system moved northeast over southern Canada,trailing a long band of moisture which streamed southwest to the Hawaiian Islands. The “PineappleExpress” dumped up to 8 inches of rain in northern California during the last week of December 1996 andthe first week of January 1997. Warm air moved over California ahead of the front and raised surfacetemperatures into the low to mid 60's by Jan 1 and caused a rapid melting of the snowpack and anincreased runoff in the mountains. The Susan, Truckee and Walker Rivers exceeded their banks andcovered the low-lying valley floors and river canyons. Thousands of residential and commercial buildingswere damaged or destroyed by the swift moving waters. The floods caused almost $1 Billion in damageto the area. Most damage occurred to roads and bridges when they were washed away as the rivers roseto record levels. Only two deaths and 50 injuries resulted from the massive flooding event.Right: Heavy rain and melting snowcaused the Walker River inMono County, CA to flowout of it’s banks near theMountain Gate community. Ittook 6 months to rebuild 14miles of US Highway 395 inWalker Canyon.(Photos courtesy of Mono CountySheriffs Department, Bridgeport, CA)5Left: A GOES-9 (GeostationaryOrbiting EnvironmentalSatellite) enhanced infraredimage of the PacificOcean and the Northwestcoast of the US. Theclouds associated with twostrong low pressuresystems are visible with acontinuous stream ofmoisture being pulled intothe Northwest US fromwest of Hawaii.(Image courtesy of the NationalClimatic Data Center, Asheville,NC)