What is the best resource to find average snowfall totals? Was 2.9” for 1980-2010 for KATL?
The 30 winters 1980-1 through 2009-10 averaged 2.6". However, the 30 years prior (1950-1 through 1979-80) averaged only 1.7" and the 30 years prior to that (1920-1 through 1949-50) averaged only 1.3". OTOH, the 30 years prior to that (1890-1 through 1919-20) averaged a whopping 3.3" due to a colder climate then as Febs especially were sig colder for some reason.
So, when you average out these four 30 year periods, you get an average for 1890-1 through 2009-10 of 2.2". So, it all depends on what period you choose to use. I think using longer than 30 years is wise due to high volatility. Furthermore, keep in mind that these numbers include sleet, which is a nontrivial portion. 1.0" Sleet accum is the equivalent of about 2.5" of snow. So, the 2.2" longterm average is likely equivalent to something closer to 2.7" or so. And I'm not even going to go into ZR, which is totally excluded in this analysis.
Also, the station was downtown ATL 1890-1 through 1933-4 followed by the further south airport 1934-5 through 2009-10. For 1890-1 through 1933-4 (downtown), the average was 2.6". From 1934-5 through 2009-10 (airport), the average was 2.1". But keep in mind that the winters were colder 1890-1912, largely due to Feb. So, some of the boost in 1890-1 through 1933-4 was colder winter related.
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Edit to add 2010-1 through 2018-9: average of 2.1", with about 0.25" of that 2.1" being sleet meaning the 2.1"/year is really equivalent to ~2.5". There was also sig. ZR in Feb of 2014, including major ZR on the southside and eastside of ATL.