StormReady
Quantitative Precipitation Forecast (QPF)
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The National Weather Service provides rainfall depth forecasts nationally for the next three days called the Quantitative Precipitation Forecast (QPF). This information is given in inches per six-hour periods. The forecasted rainfall depths can be used to estimate forecasted depth of flow at specific locations. It should be clear that the first six-hour forecast is more reliable than the last six-hours.
The water surface elevations (WSE) in lower Chicken Ranch and Strong Ranch Sloughs depend on the WSE in the D-05 pump station basin, which in turn is affected by the WSE in the American River. The California Nevada River Forecast Center (CNRFC) provides 5-day forecasts of river stage for numerous locations, including the American River at the H Street bridge, approximately 1 mile upstream of the D-05 detention basin outfall.
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Hydrologic and hydraulic computer models have been developed for lower Chicken Ranch and Strong Ranch Sloughs, including the D05 pump station. Using the QPF rainfall amounts and forecasted stages for the American River a forecasted WSE can be estimated at select locations as shown in the table below. A small concrete floodwall was constructed along the south bank of Strong Ranch Slough near Bell Street by Sacramento County Department of Water Resources in 2006 to protect Woodside properties. The top of the floodwall is at 32 feet elevation. This is approximately the same elevation of the top of banks along Sierra Branch through Woodside. So a forecasted elevation of 32 feet or greater at Northrop at Bell is a warning that flooding in Woodside is imminent. It is important to realize that these estimated flood depths are only as good as the forecasted rainfall, and should be viewed with discretion.
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Warning! This report contains provisional data from automated sources. This data has NOT been verified for accuracy.
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Forecasted Rainfall / Water Surface Elevation
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Saturday (11/21/2009) |
Sunday (11/22/2009) |
Monday (11/23/2009) |
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4 am
to
10 am |
10 am
to
4 pm |
4 pm
to
10 pm |
10 pm
to
4 am |
4 am
to
10 am |
10 am
to
4 pm |
4 pm
to
10 pm |
10 pm
to
4 am |
4 am
to
10 am |
10 am
to
4 pm |
4 pm
to
10 pm |
10 pm
to
4 am |
| 6 Hour QPF (in) |
-- |
-- |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
American River
at D-05 (ft) |
-- |
-- |
13.90 |
13.90 |
13.90 |
13.90 |
13.90 |
13.90 |
13.90 |
13.90 |
13.90 |
13.90 |
D-05 Basin
(ft) |
--
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--
|
*
|
*
|
*
|
*
|
*
|
*
|
*
|
*
|
*
|
*
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Northrop at Bell
(ft) |
--
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--
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*
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*
|
*
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*
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*
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*
|
*
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*
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*
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*
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