Peakflow Forecasts Header

BIG LOST--MACKAY RESERVOIR NEAR MACKAY
   State:  Idaho    County:  CUSTER
   Latitude:  43 57' 5" North    Longitude:  113 40' 27" West
   Elevation:  5946 feet
   Supporting WFO:  Pocatello    
   Inflow Data  

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.

BIG LOST--MACKAY RESERVOIR NEAR MACKAY   (MACI1)
Forecasts for Water Year
2026
Ensemble Date: 2026-02-06
Forecast Period: February 6 to June 1
Exceedence
Probability
Inflow
CFS
Probable
Date of Peak
95 % 1107 2026-04-19
90 % 1189 2026-04-26
70 % 1616 2026-05-11
50 % 1931 2026-05-24
30 % 2346 2026-05-29
10 % 3144 2026-06-01
05 % 3607 2026-06-01

Peakflow exceedence plot for MACI1

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