The Doppler Radar
The type of technology that is used to predict blizzards is called a Doppler Radar. The Doppler Radar predicts weather and warn people, which I will explain below. Anyway, it predicts weather when set into a certain mode. The first mode is clean air mode. Clean air mode is set when weather is fair. This mode is occasionally used for detecting light snow. It scans the atmosphere every ten minutes to give a 3D picture of the weather. The second mode is precipitation mode. Precipitation mode is set during less sensitive weather, like rain and hail. Unlike clean air mode, precipitation mode looks higher up into the horizon a little higher, though it does look at the horizon the same as clean air mode does as well. It scans the atmosphere faster than clear air mode as well: every five to six minutes. The Doppler Radar warns people about future storms and catastrophic events that can be detected by giving the data to meteorologists and the public.
Christian Doppler discovered the Doppler Effect when he was observing stars. As said in this article here, "'a shift in frequency and wavelength of waves which results from a source moving with respect to the medium, a receiver moving with respect to the medium, or even a moving medium,'" is what the Doppler Effect is.
The Doppler Radar obtains precipitation and wind info based off returned energy. How it gets that returned energy is that the radar emits a signal and if it hits an object (ex. a rain drop) the energy gets scattered and some of that energy gets reflected back to the radar and becomes received.