GrassCast is a tool that forecasts grass production on the eastern plains. This tool uses historic precipitation averages and production to make forecasts on forage production that can help inform decisions.
Historically in western Colorado, there has been little information on the production of forage in lbs/acre on rangelands in public and private hands. We’ve relied on ‘averages’ but production can fluctuate each year, meaning that ‘average’ is not that useful.
A new tool, the Rangeland Analysis Platform, can provide a starting place. It provides yearly data going back to 1986 on rangeland productivity. To make this product, researchers correlated 1,000s of ground-sampled plots (collected via the AIM program and the NRI program) with satellite images. The tool is not perfect, and it must be used in conjunction with your judgement and experience, but it provides a starting place for the amount of fluctuation and what one might expect in a drought year.
Another resource is Web Soil Survey. https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm which has low, average and high forage estimates.