Streamflow, Drought, and Water Supply Conditions

Water supply conditions as of 4/18/2018

From Jacqueline Knutson, Hydrologist, Montana Fish, Wildlife and Parks


Snowpack: At this time the Big Hole Basin is at 149% of average. The Jefferson Basin in its entirety is at 144% of average. The snowpack is holding strong and all snotel sites are well above average with occasional continued augmentation from the winter that does not want to end. With long-range forecasts indicating little change to the cool and wet pattern that has persisted throughout this winter, some additional snotel records may fall as we reach peak snowpack this spring in Montana’s river basins.


Precipitation:  Snowfall and precipitation favored the southwest portion of the state over the course of March; moist southwest flow dropped above normal precipitation in the mountains and valleys over the Jefferson River basin. Although it is now officially spring, April and May are both significant for the basin snowfall and precipitation wise and will play a critical role in determining the timing and magnitude of runoff this spring and summer. Hopefully, the wet and cool pattern will persist.


Temperatures:  Valley air temperatures for April have been below normal with average highs fluctuating a few degrees above and below the average. The outlook for the remainder of the month is similar below average temperatures.


Period of Record Monthly Climate Summary – Period of Record : 01/01/1923 to 06/09/2016

See details below from Western Regional Climate Center:


Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Average Max. Temperature (F) 26.4 31.1 38.5 49.2 60.3 68.6 79.4 77.8 67.6 55.0 38.0 28.0 51.7
Average Min. Temperature (F) 1.2 3.3 10.8 21.2 28.7 36.1 38.2 34.7 27.8 21.3 12.3 3.6 19.9
Average Total Precipitation (in.) 0.70 0.52 0.74 0.95 1.64 1.96 1.09 1.03 0.99 0.83 0.76 0.77 11.97
Average Total SnowFall (in.) 11.8 8.3 8.6 4.5 2.5 0.5 0.0 0.0 0.5 1.9 7.8 10.8 57.0
Average Snow Depth (in.) 9 10 8 1 0 0 0 0 0 0 2 5 3

Percent of possible observations for period of record.
Max. Temp.: 98.7% Min. Temp.: 98.6% Precipitation: 98.6% Snowfall: 76.4% Snow Depth: 50.3%


National Water Supply Reports

Nation-wide information for water supply and climate prediction & forecasts. 

National Weather Service Climate Prediction Center – Three Month Outlook Report


Montana Water Supply Reports

Statewide information for water supply and drought conditions. Report breaks out conditions by major basins:

Montana Water Supply Outlook Reports (March 2018)

Guide to Using the New Montana Water Supply Report

Water supply and drought condition information specific to the Upper Missouri Basin:

Upper Missouri River Basin Water Supply Report: Spring 2017

Water Monitoring Resources from the Montana Watershed Coordination Council

Montana Watershed Coordination Council Water Monitoring Webpage


Past Streamflow & Snowpack Reports

April 2018 Streamflow/Snowpack Report (PDF)

March 2018 Streamflow/Snowpack Report (PDF)

February 2018 Streamflow/Snowpack Report (PDF)

November 2017 Streamflow/Snowpack Report (PDF)

October 2017 Streamflow/Snowpack Report (PDF)

August 2017 Streamflow/Snowpack Report (PDF)

June 2017 Streamflow/Snowpack Report (PDF)

April 2017 Streamflow/Snowpack Report (PDF)

March 2017 Snowpack Report (PDF)

February 2017 Snowpack Report (PDF)

November 2016 Streamflow/Snowpack Report (PDF)

September 2016 Streamflow/Snowpack Report (PDF)

May 2016 Streamflow/Snowpack Report (PDF)

April 2016 Streamflow/Snowpack Report (PDF)

March 2016 Streamflow/Snowpack/CCAA Report (PDF)

February 2016 Streamflow/Snowpack Report (PDF)