The Columbia Basin Bulletin
The Oregon water supply for the coming spring and summer is forecast to be near-normal for northwest Oregon and portions of northeast Oregon, and below-normal for much of southwest, central and eastern Oregon, especially south-central and southeast basins, according to the most recent “outlook” produced April 11 by the NOAA National Weather Service’s Portland office.
Water supply forecasts are based on current snowpack conditions and observed precipitation thus far this winter, the agency says. Below-normal precipitation January through March has pushed several Oregon basins closer to drought conditions.
“Not surprisingly, the potential for spring snowmelt flooding in Oregon as of early April is below-normal,” according to the outlook. Springtime (May-June) flooding is typically limited to basins east of the Cascades and is usually caused by a combination of rainfall and snowmelt.
NOAA’s temperature and precipitation outlook for the spring calls for continued ENSO-neutral conditions in the tropical Pacific, meaning neither La Nina or El Nino climatic conditions hold sway. Based on this and other climate factors, there is a slightly-enhanced possibility of below-normal temperatures and below-normal precipitation for Oregon during April-June.