Official Streamflow Forecasts


Volumetric streamflow forecasts issued by the the USDA-NRCS are available for Montana Rivers and streams starting in March of each water year. Forecasts are published around the 5th business day of each month from March through June. 

There are several ways to view the forecasts. The legacy table format can be found in the monthly update report, however the forecasts can also be viewed in chart form. The charts show the entire range of outcomes and can be viewed in a spatial format, which allows you to compare forecasts within a region. Links and interactive frames to view this data can be found below. 


Monthly Forecasts - Graphical Format

Click on the image below to be directed to forecasts for your river basin of interest. This format is the favorite of SNOW program staff. It allows for easy viewing of all the exceedance forecasts issued for each point and how the distribution of those forecasts relates to the 30 year average. Viewing the entire range and distribution allows water users to consider multiple potential outcomes for their water management practices.  

A guide on how to interpret this forecast tool can be found here.

Monthly Forecasts - Interactive Map Based Format

Shown below are all streamflow forecasts for the most recent forecast period. The date of the forecast and period selected can be seen in the legend. Water users can hover over an individual point for the forecasted percentage of average, or click on the point for more detailed statistics.

Displayed is the 50% exceedance forecast for each point. To view a range of exceedance probabilities for each forecast point, please see the monthly graphic listed above or in the table format listed below. 

Monthly Forecasts - Table Format

Select state and basin of interest for the most recent date published. Select "Forecast" and a .pdf will download with the information for your selection(s). Please remember, forecast tables will only be available for most Montana basins on March 1st through June 1st.