VDRAS relies on data assimilation, a technique for combining real-world observations and computer model output to create a more accurate forecast.

VDRAS has a very fast update cycle, providing new data from real-time radar and other sources for assimilation every 6–12 minutes. The mathematical technique it relies on, called 4DVar (Four-Dimensional Variational), is the gold standard for the field of data assimilation. The system uses freely available observations from the National Weather Service's Doppler radar network, so it can be run anywhere in the country without requiring new and costly instrumentation.

VDRAS works with these two other NCAR-based tools: the advanced research version of the Weather Research and Forecasting model, which generates very detailed predictions of areas as small as 3 kilometers (1.8 miles) square; and the Dynamic Integrated ForeCast system, which fine-tunes and optimizes the ongoing forecast.