GENERAL OUTLOOK
Wet conditions prevailed over the Columbia-Snake basin through February. Near average temperatures allowed snow to continue to accumulate at near record rates in some areas. This is reflected in moderate increases in expected volume over the entire basin.
Precipitation for the month was at near record levels west of the Cascades and well above average east of the Cascades. The driest area in the basin was the Columbia River in Canada at 115 percent and the wettest areas were western Oregon, northeast Oregon and southern Idaho, with 180-200 percent of average. The seasonal total for the Columbia River above The Dalles is 123 percent.
Several individual snow courses set records for the March 1st accumulation period. The Cascade mountains in southwest Washington and Oregon have snow water equivalents at twice average. Most of the basin reports snow water equivalents in the 130 to 180 percent range, only the southern Snake River area and parts of the Clark Fork River in Montana have lower snow water equivalents. February runoff was above average for most of the basin. Only western Montana and the Yakima river area in Washington had below average runoff.
March 1st volumes increased basin wide. The greatest increases of 20 - 30 percent occurred in eastern Oregon and in southern Idaho. Smaller increases were observed in western Montana and in the Upper Columbia area. The January - July forecast for The Columbia River above The Dalles is 130.0 MAF or 123 % of average. This is an increase of 10 percent from last month and compares to a runoff of 104.1 MAF in 1998.
A progressive westerly storm pattern resulted in what seemed to be never-ending precipitation with somewhat above normal temperatures focused across western and occasionally into central basins. Mean temperatures departed +1.7 degrees (31 stations) from normal for the Pacific Northwest relative to 1961-1990 normals. Mean temperature departures ranged from -7.2 to 7.1 degrees.
Astoria saw record daily rainfall on the 1st (0.97 inches)...on the 2nd (1.66 inches)...on the 22nd (1.80 inches)...and on the 27th (1.28 inches)...Salem on the 27th (1.41 inches)...and Missoula on the 23rd (0.39 inches). This was the wettest February on record for Olympia (15.50 inches)...the 3rd wettest for Salem (11.40 inches) and the 4th wettest for Portland airport (8.73 inches). No temperature records were reported at the time this report was prepared.
Frequent pacific frontal disturbances produced significant cumulative valley rain and mountain snow across most of our basins through February. The primary exception to this generally record warm wet La Nina pattern were drier than normal conditions along the front range of the Rockies east of the continental divide in western Montana where arctic air outbreaks seemed to dominate local weather conditions. West of the continental divide active warm front resulted in occasional rain on snow and elevated snow lines that resulted in some significant low elevation snow melt runoff but higher elevation snow packs continued to build above normal accumulations across the region.
For February, precipitation was 137 percent of normal (1961-1990) at Columbia above Coulee; 185 percent of normal at the Snake River above Ice Harbor; and 156 percent at Columbia above The Dalles.