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SOUTH PRAIRIE--AT SOUTH PRAIRIE
   State:  Washington    County:  PIERCE
   Latitude:  47 7' 59" North    Longitude:  122 4' 59" West
   Elevation:  430 feet
   Supporting WFO:  Seattle    
   Action Stage:  28.88'   Flood Stage:  29.64'   Moderate Flood Stage:  30.5'
   Major Flood Stage:  31.63'

Forecasts are calculated from a forecast time series that approximates flow at a 6 hour time step interval. Observed instantaneous peaks can be higher than model forecast peaks.

SOUTH PRAIRIE--AT SOUTH PRAIRIE   (SPEW1)
Forecasts for Water Year 2025
Ensemble Date: 2025-07-11
 Forecast Period: July 11 to November 1
Exceedence
Probability 		Stage
feet 		Discharge
CFS 		Probable
Date of Peak
95 % 24.15 87 2025-09-05
90 % 24.23 102 2025-09-28
70 % 24.94 246 2025-10-17
50 % 25.78 488 2025-10-23
30 % 26.01 598 2025-10-27
10 % 26.76 999 2025-10-31
05 % 27.87 1741 2025-11-01

Peakflow exceedence plot for SPEW1

 Click to download runoff traces used in forecast.  Click for comma delimited data used in plot.csv icon