Missouri River Region Mountain Snowpack Report

2015-2016 Mountain Snowpack Report for Missouri River Basin

 

Winter of 2015-2016.The May 1 forecasted runoff for the Missouri River Basin above Sioux City, IA for calendar year 2016 is 22.5 MAF, 89% of average. The Missouri River Basin mountain snowpack normally peaks near April 15. By May 1, normally 97% of the peak has accumulated. On May 1, 2016 the mountain snowpack Snow Water Equivalent (SWE) in the Above Fort Peck Dam reach was 75% of the average May 1 SWE. The mountain SWE in the Fort Peck to Garrison reach is currently 87% of the average May 1 SWE. The following tabulation is a summary of this year's mountain SWE accumulations and the CY 2016 runoff forecast for the first of each month.

 

CY 2016 Mountain Snowpack Accumulations in Percent of Average SWE

Reach

Jan 1

Feb 1

Mar 1

Apr 1

May 1

Jun 1*

Jul 1*

 

Peak Accum.*

Peak Date

Above Fort Peck Dam

100%

92%

89%

95%

75%

 

 

Fort Peck to Garrison

76%

72%

75%

89%

87%

 

 

*Percent of Normal April 15 Peak

Forecasted CY 2016 Upper Missouri River Basin Annual Runoff in MAF

Location

Jan 1

Feb 1

Mar 1

Apr 1

May 1

Jun 1

Jul 1

Aug 1

Sep 1

Above Sioux City, Iowa

23.8

23.3

21.6

21.7

22.5

 

 

 

Percent of Average,†††† 25.3 MAF

94%

92%

85%

86%

89%

 

 

 

 

For comparison purposes, the mountain SWE for the previous two years were:

CY 2014 Mountain Snowpack Accumulations in Percent of Average SWE

Reach

Jan

Feb

Mar

Apr

May

 

Peak Accum*

Peak Date

Above Fort Peck Dam

110%

107%

122%

133%

138%

 

132%

Apr 7

Fort Peck to Garrison

113%

113%

133%

140%

142%

 

140%

Apr 17

*Percent of Normal April 15 Peak

 

CY 2015 Mountain Snowpack Accumulations in Percent of Average SWE

Reach

Jan

Feb

Mar

Apr

May

 

Peak Accum*

Peak Date

Above Fort Peck Dam

99%

93%

88%

68%

54%

 

72%

Mar 9

Fort Peck to Garrison

101%

96%

97%

74%

62%

 

78%

Mar 9

*Percent of Normal April 15 Peak

 

SNOTEL Mountain snowpack SWE station data is provided by the USDA Natural Resource Conservation Service (NRCS).Normally by April 15, 100% of the peak mountain snowpack SWE accumulation has occurred.

The snow melts during the May through July timeframe and provides significant Mainstem inflow, which is stored to prevent downstream flooding and later used to meet the Mainstemís authorized project purposes.Knowing the amount of mountain SWE at the first of each month for selected mountain snowpack areas does not reduce the considerable runoff variability because the weather conditions during the melt period greatly influences the runoff yield.The total percent of average SWE accumulation are shown for the first of each month through May.For the period of May through July, the percentages recorded are a percent of the peak SWE accumulation for the year.This indicates the remaining amount of snow to melt in the mountains.