The returned energy which is measured by the radar is given by the so-called "radar equation" which states that:
$P_r=\frac{CK_w^2}{r^2}\sum_{i=1}^Nn_iD_i^6$
Here $C$ is "just" some antenna characteristics and $r$ is the distance from the radar.
$K_w$ is the dielectric constant, which differs for rain and snow. For rain it is approximately 0.93. For snow, $K_w$ varies much more depending on type of snow i.e. wet or dry snow. So that is the first thing that complicates things when it comes to snow.
Secondly, the last term, which is the reflectivity factor $Z=\sum_{i=1}^Nn_iD_i^6$ also cause some trouble.
There is a well known empirical formula for the relation between the reflectivity factor and the precipitation rate, $R$, given as:
$Z=aR^b$
where $a$ and $b$ are constants determined empirically. However, these are not very well determined. Fujiwara (1965) found that $a=450$ and $b=1.48$ for stratiform rain and $a=300$ and $b=1.37$ for rain showers. These "constants" are even less well-defined for snow and the many varieties that exist.
To conclude I would say that while estimating the intensity of snowfall can be done, the estimation is much more uncertain than in the case of rainfall, probably making it practically useless. The main reasons are the dielectric constant and $a$ and $b$ in the above formula.
And for fun: Plugging in numbers in the radar equation, one can see that 729 drops with a diameter of 1mm have the same reflectivity as 1 drop with a diameter of 3mm!
Battan, L. J., Radar observation of the atmosphere, p. 44-85. The University of Chicago Press, 1973.
Fujiwara, M. Raindrop-size distribution from Individual Storms. Journal of the atmospheric Sciences, 1965.