Peakflow Forecasts Header

CHEHALIS--NEAR GRAND MOUND
   State:  Washington    County:  THURSTON
   Latitude:  46 46' 33" North    Longitude:  123 2' 9" West
   Elevation:  124 feet
   Supporting WFO:  Seattle    
   Action Stage:  138.5'   Flood Stage:  141'   Moderate Flood Stage:  142.5'
   Major Flood Stage:  144'

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.

CHEHALIS--NEAR GRAND MOUND   (CGMW1)
Forecasts for Water Year 2025
Ensemble Date: 2025-05-12
 Forecast Period: May 12 to September 1
Exceedence
Probability 		Stage
feet 		Discharge
CFS 		Probable
Date of Peak
95 % 130.06 616 2025-05-19
90 % 130.06 616 2025-05-19
70 % 130.10 639 2025-05-26
50 % 130.52 886 2025-06-04
30 % 131.19 1384 2025-06-13
10 % 132.31 2508 2025-06-19
05 % 132.97 3354 2025-06-28

Peakflow exceedence plot for CGMW1

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