After watching Game of thrones S06 E09 "The Battle of Bastards", I cannot help but remember S05E10 "Mother's Mercy" where we see Stannis's Battle of Winterfell. That episode showed winterfell in much snow and the entire ground was covered in snow. However, in this episode there is much less snow falling and land less covered in snow.
Has it stopped snowing? Was the venue for this battle different than that the previous one? Or was it just a continuity error?
In the books, at around this time in the sequence of events (I know it's not entirely consistent with the show, but assuming they are at least a similar timeline) it has become Autumn.
In the famous words of the Starks: 'Winter is Coming'... but it's not here yet. This means that there are terrible blizzards coming in, but the weather is not so bad yet that there is constant snow.
Whether or not it was Melisandre who allowed the storm in S05 E10 to recede and the snow to melt, or just the natural weather patterns, is open to speculation. But the blizzard that came was just a single occurrence. As Winter draws closer there will be more and more, up until the point when it is a struggle to survive as the ground is covered in snow for years at a time.
Seeing as how it is not Winter yet, the snows will still come and go, which is why the grounds at Winterfell are simply covered in a dusting of snow instead of it being very thick.
