GENERAL OUTLOOK
Snow water equivalent percentages increased slightly across northern portions of the basin and decreased 3-15 percent in the southern areas of the basin. The best improvements in snow pack occurred in the Upper Columbia, Kootenai and Flathead river basins, which are important contributors to the total flow on the Columbia River at The Dalles. Some snow depths across the basin at the end of the month: West Yellowstone 30 inches, Crater Lake 110 inches, Paradise Ranger Station 190 inches, Stampede Pass 106 inches, Blue River B.C. 25 inches.
Observed stream flow for March was above average on the Upper Columbia, some Middle Snake rivers and on the Blue Mountain tributaries. Most of the basin had below average runoff during March. The adjusted flow for the Columbia River at The Dalles was slightly below average.
Volume forecasts improved slightly for the Upper Columbia - Kootenai and the Flathead rivers. The Snake river tributaries generally dropped 3 - 5 percent. This resulted in a January - July forecast for the Columbia River at The Dalles of 105 million acre feet or 99 percent of average. This compares to a runoff of 124.1 million acre feet in 1999.
Pacific Northwest mean temperatures departed +2.6 degrees from normal relative to 1961-1990 normals (31 stations). Mean temperature departures ranged from -3.1 to 13.1 degrees.
Below normal precipitation was evident across much of the Pacific Northwest during March. Notable exceptions included much of central and eastern Washington and Oregon as well as southern British Columbia, where precipitation was over 130 percent of normal in a few locations.
Temperatures were above normal across much of Idaho and western Montana and near normal elsewhere east of the Cascades. West of the Cascades, temperatures were below normal.
Early in the month, a series of frontal systems brought abundant precipitation to western Washington and northwest Oregon. Precipitation was much lighter elsewhere across the region. During the middle of the month, precipitation started out being rather light as a cut off low pressure system developed across the desert southwest and the main storm track lifted north of the region. As this system lifted out of the southwest, a series of frontal systems once again began effecting the region. Moderate to locally heavy precipitation returned to western Washington, northwest Oregon, and higher elevations east of the Cascades.
Late in the month, occasional showers occurred, especially across northern tier basins. Otherwise, a ridge of high pressure was fairly dominate through the latter part of the month. No temperature or precipitation records occurred in the month of March.
For March, precipitation is: 111 percent of normal (1961-1990) at Columbia above Coulee, 86 percent of normal at the Snake River above Ice Harbor, and 103 percent at Columbia above The Dalles.
For the water supply season, precipitation is: 111 percent of normal (1961-1990) at Columbia above Coulee, 95 percent of normal at the Snake River above Ice Harbor, and 104 percent at Columbia above The Dalles.