Where are snowfall data in the southwestern United States and Mexico located?

I would suggest looking in the Global Summary of the Day data in our Data Library.

The data include daily weather summaries, including snow depth, for stations around the globe, including Mexico. Whether these stations are in locations that receive snow, or where the measurements were actually taken might be another matter. In any case, see the following:

http://ingrid.ldgo.columbia.edu/SOURCES/.NOAA/.NCDC/.DAILY/.GLOBALSOD/

You can then get data for stations in your desired region by searching via lat/lon limits. See this Q&A entry for further explanation.

-- Michael Bell