GENERAL WEATHER SUMMARY
March 1, 2000
It was a warmer and wetter than normal February. A split jet stream ushered a series of generally week low pressure systems into the northern and southern tiers of the basin early in February. By mid month, and through the end of the month, the weather pattern shifted to a more zonal flow bringing rain to the basin valleys and snow to the mountains. Low pressure systems came onshore with frequency of every other day toward the later part of the month.
Pacific northwest mean temperatures departed +2.4 degrees from normal relative to 1961-1990 normals (31 stations). Mean temperature departures ranged from -3.3 to 8.4 degrees.
No temperature or precipitation records occurred in the month of February.
For February, precipitation is: 94 percent of normal (1961-1990) at Columbia above Coulee, 142 percent of normal at the Snake River above Ice Harbor, and 111 percent at Columbia above The Dalles.
For the water supply season, precipitation is: 110 percent of normal (1961-1990) at Columbia above Coulee, 97 percent of normal at the Snake River above Ice Harbor, and 104 percent at Columbia above The Dalles.
March 1st snow conditions are somewhat below to near average for most of the basin. The exception is in Oregon and southwest Washington where March 1st snow water equivalents are in the 100 to 130 percent range. In the Upper Columbia-Kootenai, Pen Oreille and Spokane areas, snow accumulations during February were slightly below average while snow improved by 5 - 15 percent in other areas.
Some snow depths across the basin at the end of the month: West Yellowstone 27 inches, Crater Lake 134 inches, Paradise Ranger Station 176 inches, Stampede 100 inches, Blue River B.C. 33 inches.
Above average temperatures and generally above average precipitation caused above average runoff for most of the Columbia River area above Coulee, the Upper Snake and on western Oregon tributaries. Other areas had February runoff ranging from 70 to 85 percent of average.
Runoff volumes in general decreased slightly on the Columbia River and increased by 5 - 15 percent on the Snake River. The January - July runoff for the Columbia River above The Dales is at 105.0 million acre-feet or 99 percent of average. This is down 1 percent from February 1st. This compares to a runoff volume of 124.1 million acre feet last year.