Precipitation and streamflow averaged above normal throughout Washington in the 1996 water year (October 1995 to September 1996). Overall, the year was one of the wettest recorded, and heavy precipitation produced floods in many parts of the State in November, December, January, February, April, and May. Floods in late November and early February were the most severe, producing peaks of record at many gaging stations. Snowpack in the mountains averaged above normal and helped produce average to above average flows throughout the summer at most gaging stations in the State. Average streamflows vary in the State depending on geography, topography, precipitation, and air temperature patterns.

The 1996 water year realized many periods of high water and flooding throughout Washington in a year of above normal precipitation. Baring, on the west slope of the Cascade Range, received over 150 inches of precipitation during the year, comparable to wetter places on the west side of the Olympic Mountains (National Oceanic and Atmospheric Administration, 1995). The wettest month was November, with some areas along the west slope of the Olympic Mountains and Cascade Range receiving over 30 inches of rain -- Baring received almost 41 inches (National Oceanic and Atmospheric Administration, 1995). November, along with February, also experienced the worst flooding in the State. At some stations, November produced the highest peak, but for most, it was in February. The combination of heavy rainfall and high snowmelt in February produced record-setting peak discharges at many stations in the southern half of the State. The driest months were March, June, and July.

Streamflows during November were above average throughout the State except for the northeast quarter, where they were average. Flows approached or exceeded peaks of record for some stations due to very heavy rainfall from three series of storms (November 5-8, 10-11, and 27-30). Several locations on the west side of the Olympic Mountains and Cascade Range received over 30 inches of rain during the month. About 10 inches of rain were recorded in the Puget Sound region. Peak streamflows on November 29-30 approached peaks of record in the Snoqualmie, Sauk, upper Nooksack, and Cowlitz River Basins and exceeded instantaneous peaks of record at some stations in the Skagit, lower Nooksack, and Wenatchee River Basins.

In December and January, rains continued, but precipitation averaged only slightly above normal in the State. Several stations on the west side of the Olympics received over 20 inches of rainfall in December and again in January. Streamflows averaged above the mean throughout the State in December and ranged from normal to above normal in January. Streamflow at several stations in small basins approached or exceeded instantaneous peaks of record in December -- Canyon Creek near Cedar Falls (station 12116100, December 4, 107 ft3/s, peak of record is 131 ft3/s), Boxley Creek near Edgewick (station 12143900, December 3, 260 ft3/s, new record), and Duckabush River near Brinnon (station 12054000, December 12, 9,240 ft3/s, new record). Arctic air moved into the State on January 27, producing some snow on January 27-29, but brought clearer skies and extremely cold temperatures afterward. The air temperature at Davenport, near Spokane reached -28 degrees Fahrenheight (degrees F) on January 31 (National Oceanic and Atmospheric Administration, 1996). Hydrographs for all stations in the State dropped during this period as freezing weather prevented snowmelt and, along with drier weather, reduced streamflows.

The cold weather continued into early February, but was soon replaced by a warmer, very wet series of storms February 5-9 that produced heavy rain, high rates of snowmelt, and record flooding throughout much of the State. Streamflows were above normal throughout Washington except for the northwest corner. Very heavy rains on February 5-9 -- Cougar, 18 inches; Packwood, 12 inches; Baring 15 inches; SeaTac, 6 inches; Plain, 6 inches (National Oceanic and Atmospheric Administration, 1996) on already saturated ground in western Washington, or on frozen ground in eastern Washington accompanied by snowmelt induced by the rain and warmer air (freezing levels above 6,000 feet) produced high flows at most stations in the State. On February 8-9, flows at many stations in the southern half of the State exceeded the peak flow of record. At a number of stations, such as in the Cowlitz Basin, peak February flows were just slightly higher than the near-record peak flows in late November. At many gaging stations in western Washington, the February flooding was the worst since November, 1990, when some stations in the Skagit and Nooksack River Basins in northern Washington recorded their peak discharges of record. At many eastern Washington stations, peak flows were below the peak of record, such as at Tucannon River near Starbuck (station 13344500, 5,580 ft3/s, on February 9, peak of record 7,980 ft3/s on December 22, 1964). At some stations where temperatures remained near freezing, only a little rise in streamflow was noted on February 8-9 (Methow River near Pateros).

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