National Weather Service United States Department of Commerce

Missouri Basin River Forecast Center
Water Supply Statement
Issued in cooperation with the Natural
Resources Conservation Service
Issued:  December 28, 2020


 Upper Missouri Basin

November precipitation across the Upper Missouri Basin was above average. Basin precipitation summaries for the Missouri Basin include: Milk St. Mary, 136 percent; Milk Canada, 287 percent; Lower Milk, 158 percent; above Toston, 75 percent; Toston to Ft. Peck, 144 percent. 

Of the four major irrigation reservoirs in Montana; Lima Reservoir had 139 percent average storage, Clark Canyon was holding 116 percent of average water, Gibson Reservoir had 87 percent of average stored water, and Fresno Reservoir had 61 percent of average stored water.

The major hydroelectric reservoirs in Montana (Canyon Ferry and Fort Peck), had monthend storage in the average to above average range; 94 and 112 percent of average water, respectively.

Yellowstone Basin 

Precipitation during November was below average. The upper Yellowstone River Basin received 80 percent of average precipitation while the Lower Yellowstone River Basin reported 49 percent of average. The Bighorn Basin received 32 percent of average precipitation while the Wind River Basin received 38 percent of average. The Little Bighorn - Upper Tongue Basin received 24 percent of average and the Powder River had 14 percent of average precipitation.

Monthend storage at Boysen Reservoir was 95 percent of average. Stored water in Buffalo Bill Reservoir was 121 percent of average. Monthend storage was 97 percent of average at Bighorn Reservoir.


Platte Basin 

Precipitation during November in the Upper North Platte Basin was 56 percent of average.  In the Lower North Platte Basin, precipitation was 25 percent of average.  The North Platte Plains below Guernsy Reservoir had 21 percent.  The South Platte Mountains had 93 percent whereas the Plains had 60 percent of average November precipitation.

Stored water in the South Platte Basin was 95 percent of average on December 1.


November 2020  WY 2021
November 2020 Precipitation Percent of 1981-2010 Average WY2021 Precipitation as Percent of 1981-2010 Average
November 2020 Basin Mean Precipitation          WY2021 Basin Mean Precipitation
November 2020 MBRFC Basin Mean Precipitation      WY2021 MBRFC Basin Mean Precipitation