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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 2026
Ensemble Date: 2026-03-14
 Forecast Period: March 14 to July 1
Exceedence
Probability 		Stage
feet 		Discharge
CFS 		Probable
Date of Peak
95 % 28.08 1780 2026-03-14
90 % 28.08 1780 2026-03-14
70 % 28.08 1780 2026-03-14
50 % 28.08 1780 2026-03-14
30 % 28.08 1780 2026-03-14
10 % 28.20 1859 2026-03-31
05 % 30.82 3837 2026-05-05

Peakflow exceedence plot for SPEW1

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