Beneficial rain and snow has increased the water supply volumes slightly for most of the basin. Soil moisture deficits from last years near drought will still diminish Spring runoff somewhat.
PRECIPITATION SUMMARY
WARMER THAN NORMAL JANUARY ACROSS ALL BUT SOUTHWEST BASINS
WET JANUARY WEST OF THE CASCADES AND ACROSS NORTHERN IDAHO
Frequent episodes of valley rain and mountain snow impacted west side basins and brought precipitation to above normal levels. Storm systems weakened and did not have as much moisture to work with as they moved east of the Cascades. Precipitation was below normal from Eastern Washington and Oregon into Southern Idaho and Western Montana.
The 31 station temperature index for the Pacific Northwest departed +2.5 degrees from normal relative to the 1971-2000 normals. Mean temperature departures ranged from -3.2 to 5.9 degrees.
There were several new high temperature records established in January. They included: 56 at Olympia and 57 at Seattle on the 6th and 54 at Klamath Falls, 57 at Olympia, 59 at Seattle, 60 at Great Falls, 62 at Havre, and 65 at Medford on the 7th.
There was just one new low temperature record established in January. Meacham reported -14 on the 29th.
Daily rainfall records established in January included: 1.95 inches at Olympia on the 7th and 2.47 inches at Olympia on the 24th.
For JANUARY, PRECIPITATION was:
101 percent of normal (1971-2000) at COLUMBIA ABOVE COULEE, 91 percent of normal at THE SNAKE RIVER ABOVE ICE HARBOR, and 94 percent at COLUMBIA ABOVE THE DALLES.
For the WATER SUPPLY SEASON, PRECIPITATION was:
94 percent of normal (1971-2000) at COLUMBIA ABOVE COULEE, 105 percent of normal at THE SNAKE RIVER ABOVE ICE HARBOR, and 101 percent at COLUMBIA ABOVE THE DALLES.
SNOW SUMMARY
Snow water equivalents increased 5 to 15 percent in the northern portions of the basin and 10 to 30 percent in most of the Cascade range in Oregon and Washington. Contrasting with that are drops of 3 to 10 percent in most of the Snake River basins. Basin snow packs on February 1st range from 90 to 120 percent in most northern areas, 120 to near 200 percent in the Cascade drainages and 90 to 130 percent in most Snake River basins.
RUNOFF
Natural runoff improved somewhat during January. Most basins had monthly runoff in the 85 to 110 percent range. The lowest monthly runoff is in the Snake River basin, where percents range from 50 to 90 percent of average.
January snow and precipitation conditions have increased streamflow forecasts slightly. The exception is the Upper and Middle Snake area, where volumes dropped 2 to 15 percent. The January-July volume forecast for the Columbia River at The Dalles is 101. million acre-feet or 94 percent of average, up 2 percent from January 1st. This compares to a runoff of 58.2 million acre-feet during water year 2001.