GENERAL OUTLOOK
Several active storms brought beneficial rain and snow to northern Columbia-Snake basin. Except for a few areas on the Snake river tributaries, volume forecasts increased 2 to 15 percent from March 1st conditions. The main stem Snake River volume forecasts dropped 3 percent from March 1st.
PRECIPITATION SUMMARY
A trough of low pressure at upper levels of the atmosphere maintained a cool northwest flow across the Pacific Northwest through much of the month. Storm systems had their greatest impact across the north. Southern British Columbia, Northern Washington, Northern Idaho, and Northwest Montana reported above normal precipitation.
March, precipitation was: 115 percent of normal (1971-2000) at Columbia above Coulee, 97 percent of normal at the Snake river above Ice Harbor, and 108 percent at Columbia above The Dalles.
Water supply season, precipitation was: 99 percent of normal (1971-2000) at Columbia above Coulee, 95 percent of normal at the Snake River above Ice Harbor, and 99 percent at Columbia above The Dalles.
Daily precipitation snow records established in March all occurred on the 20th. These included: 5 inches of snow at Missoula and 6.8 inches of snow at Great Falls.
TEMPERATURE SUMMARY
The 31 station temperature index for the Pacific Northwest departed -5.2 degrees from normal relative to the 1971-2000 normals. Mean temperature departures from normal ranged from -9.5 to -2.3 degrees.
There were several new high temperature records established in March. They included: 70 at Astoria and 72 at Salem on the 6th and 69 at Portland and 71 at Eugene and Salem on the 7th.
There were several new low temperature records established in March. They included: -2 at Pocatello on the 3rd, -21 at Havre on the 21st, and -16 at Great Falls, -14 at Havre, 4 (tie) at Kalispell, and 28 (tie) at Astoria on the 22nd.
SNOW SUMMARY
April 1st snow water equivalents increased 2 to 20 percent from March 1st conditions. Basin snowpack is greatest in Canada, the Spokane, lower Pend Oreille river basins and in the North Cascades in Washington. April 1st snow water equivalents in this area range from 110 to 140 percent. The lowest April 1st snow levels are in the Upper Snake at 80 to 90 percent of normal.
STREAMFLOW SUMMARY
Streamflow for the month of March continued the below average trend of previous months. Cooler than average temperatures allowed snow accumulations to continue even down to low elevations. This limited early season snow melt.
Streamflow volumes on April 1st have risen 2-25 percent from March 1st in the northern basins and dropped 3 percent on the Snake River. The January-July volume forecast for the Columbia river above The Dalles is 96.4 million acre-feet or 90 percent of the 1971 -2000 average. This is a decline of 1 percent from March 1st. This compares to a runoff of 58.2 million acre-feet during water year 2001.