A very wet “pineapple express” from the Hawaiian Islands is going to hit Renton and the rest of Western Washington tonight and stick around for the next several days.
It won’t be particularly windy; highs will be in the mid 40s to mid 50s and lows in the 40s or upper 30s through Friday.
The heaviest rainfall is predicted for Saturday night and Sunday. The National Weather Service is forecasting 1 to 3 inches of rain will fall in the lowlands, with 4 to 9 inches in the mountains. There is already a large snowpack in the Cascades. The snow level is expected to rise to about 8,000, well above all Cascade Mountain passes.
The U.S. Army Corps of Engineers, which operates the Howard Hanson Dam on the Green River, does not expect the rainfall in the Green River basin to be a concern for operations at Howard Hanson Dam or for flooding on the lower Green River basin, which includes Auburn, Kent, Renton and Tukwila.
In addition, the flows expected in this part of the basin are below thresholds that may be of concern for levee problems, according to a corps press release. The Green River was extensively sandbagged and fortified because of the damage to the support abutment at the dam with occurred in the winter of 2009-10.
Minor urban, street, and small stream flooding is possible, which will be dealt with by local agencies.
The corps has placed its Western Washington flood teams on alert and begun preparations to deploy as needed if requested by local officials. All Western Washington river basins are being monitored.
The corps Seattle District also plans to activate its Emergency Operations Center to coordinate all corps activities. The Seattle District Reservoir Control Center is expected to go into 24-hour operation by Sunday.
If the heavy rain does cause rivers to rise, King County road crews will patrol roads in low-lying unincorporated areas that are particularly vulnerable to flooding. If road closures do become necessary, it may take a couple of days or more for the water to recede so they can be inspected for damage and reopened.
Certain areas along the Cedar River are prone to flooding between Renton and Maple Valley, including near Jones Road.
The National Weather Service has issued a flood watch for Western Washington through Monday afternoon. A flood watch means conditions are favorable for flooding, but flooding is not imminent or occurring.
When wet weather brings rivers up to certain levels, the King County Department of Natural Resources and Parks opens the Flood Warning Center to provide round-the-clock coordination of weather and river flooding information.
The center is designed to give citizens at least two hours warning to prepare for possible flooding. And it works in tandem with the County's Road Services Division, to give citizens up-to-date information about road closures.
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