GENERAL OUTLOOK
Runoff conditions improved slightly for some northern Columbia River basins as
precipitation and snow accumulations improved somewhat. However, Oregon and
Central-Southern Idaho basins continued to have declines in runoff volume
forecasts. Several sites in the basin will have runoff at or below the
previous minimum of record.
WARM AND DRY MARCH
Like January and February, the Pacific Northwest came under the influence of a
split flow. Storm systems traveling along in the northern stream brought
enough valley rain and mountain snow to bump up precipitation totals to near
normal levels across far northern tier basins. The remainder of the region
experienced drier than normal conditions as storm systems tracked from the
Eastern Pacific Ocean into the Southwest United States.
Pacific Northwest mean temperatures departed +1.8 degrees from normal relative
to 1961-1990 normals (31 stations). Mean temperature departures ranges from
-0.4 to 4.3 degrees.
There were 7 record high temperatures tied or broken in March. They include:
72 at Salem and 70 at Astoria on the 6th, 71 at Salem (tie) and Eugene and 69
(tie) at Portland on the 7th, 70 at Havre on the 19th, and 72 at the Dalles
(tie) on the 22nd.
There were 3 record low temperatures tied in March. They all occurred on the
22nd and include: 22 at Astoria, 24 at Olympia, and 27 at Quillayute.
No precipitation records were tied or broken in March.
For MARCH, PRECIPITATION is:
84 percent of normal (1961-1990) at COLUMBIA ABOVE COULEE,
71 percent of normal at THE SNAKE RIVER ABOVE ICE HARBOR, AND
82 percent at COLUMBIA ABOVE THE DALLES.
For the WATER SUPPLY SEASON, PRECIPITATION is:
59 percent of normal (1961-1990) at COLUMBIA ABOVE COULEE,
72 percent of normal at THE SNAKE RIVER ABOVE ICE HARBOR, AND
61 percent at COLUMBIA ABOVE THE DALLES.
Northern areas of the basin had slight improvements in snow water equivalent
percentages. In contrast, percentages dropped in Oregon and Central-Southern
Idaho, where percentages fell 15 to 30 percent. Several snow reporting sites
in British Columbia report April 1st snow water equivalents at or below the
previous minimum of record.
Warmer temperatures combined with rainfall brought some increases in natural
streamflow. The lowest runoff in March was on the Flathead River and Lower
Pend Oreille Rivers in Montana, the Spokane and main stem Snake Rivers in
Idaho at 40 to 50 percent. The highest March runoff was in the Upper Columbia
in Canada, the Upper Snake, Salmon and Clearwater Rivers in Idaho at 80 to 100
percent. The March adjusted runoff for the Columbia River at The Dalles was 54 percent.
Some slight increase in forecast volumes occurred on some Northern basins,
while Oregon and most Idaho drainages had a drop of 5 to 15 percent in volumes
from the March 1st forecast. The April 1st forecast for The Columbia River at
The Dalles is 56.1 million acre-feet (MAF) or 53 percent. That is a drop of 2
percent from March 1st. This compares to a runoff of 98.0 MAF last year.