... The Flood Warning remains in effect until 145 PM PDT Thursday
April 17 for the North Fork stillaguamish river east of the State
Route 530 slide in north central Snohomish County...
Flooding continues on the North Fork of the stillaguamish river
upstream of the sr 530 slide due to debris from the State Route 530
slide partially blocking the river and the resulting pooling of
water behind the debris dam. We will be updating the Flood Warning
on a day to day basis.
The latest forecast is a significant change from the last few days.
Forecast rainfall amounts for the slide area and mountains are for
just under a half inch tonight... three quarters of an inch
Wednesday... and one inch Thursday. In response... the river will
start rising tonight... then rise sharply Thursday... cresting
Thursday night before midnight with the largest flows since the
slide occurred. The peak flow forecast for the North Fork river
near Arlington gage is near 12000 cfs and near 7700 for the North
Fork stillaguamish river at Oso.
At 1000 am PDT... the pool elevation was 284.67 ft.
The pool elevation is forecast to rise to 285.0 ft. By 500 am
Thursday then rise sharply to 287.7 ft. By Thursday night before
midnight. The pool elevation will start dropping significantly
Friday. There is a great amount of uncertainty in the forecast pool
elevation crest due in part to limited knowledge of how much water
the new stream channel through the slide debris will be able to
For the latest river stages and forecasts... visit (all lower case)
weather.Gov/Seattle and go to the rivers and lakes section.
A Flood Warning means flooding is occurring or imminent. Most flood
related deaths occur in automobiles. Do not attempt to cross water
covered bridges... dips... or low water crossings. Never try to cross a
flowing stream... even a small one... on foot. To escape rising water
move up to higher ground.
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