Pacific Northwest Spring Flood Potential

Main Content
Release date: 
March 9, 1999
Release Number: 
HQ-99-064

WASHINGTON, D.C. -- The National Weather Service (NWS) reports very wet conditions in the Pacific Northwest, and the continuing influence of La Ni?a, could result in some spring flooding over the next several weeks. Since December, western Washington and Oregon have seen nearly continual precipitation, resulting in much above normal totals and some locations may establish new records this year. However, the frequent precipitation has been of moderate intensity, resulting in little severe flooding so far this season.

The stage is set though for possible major flooding later in the spring. River flows are high in many basins of northwestern Oregon and southwestern Washington, and soils are saturated. Water contained in the snow pack from the central Sierra Nevada Mountains northward through the Cascades of Oregon and Washington is up to 150 percent above normal. This is especially true in the western slopes of the Cascades.

Hydrologists at the NWS Office of Hydrology point out that snowmelt flooding in this region has historically been limited to areas east of the Cascade crest and seldom occurs before April or May. West of the crest, in the saturated coastal regions, warm temperatures and melt of lower-level snows alone would not cause significant flooding. Any major flooding west of the Cascades would have to be driven by excessive rain, with the snowmelt at most making a moderate contribution, according to the latest spring flood outlook for the region.
Last Updated: 
July 16, 2012 - 18:46