Tom Thomson at Achray in 1916, Appendix
Abstract: There are several Tom Thomson sketches that have the correct feel to be of Grand Lake and yet are sufficiently generic to preclude location, especially considering the vegetation changes over the last 100 years. They are included here.
Tamaracks

Perhaps near the mouth of Johnston Creek on Grand Lake.
Tamarack Swamp

Perhaps near the mouth of Johnston Creek on Grand Lake.
Lake in Autumn

Perhaps near the mouth of Johnston Creek on Grand Lake.
In an article (Spotlight on Two Tom Thomson Masterpieces) in the National Gallery's magazine, it is suggested that this sketch was "not likely painted out of doors" and it is an imagined colour scheme and that this colour scheme influenced the transition of the Jack Pine sketch to the Jack Pine studio painting.
We see nothing in this sketch to suggest that it was not painted out of doors nor do we see problems with the colour scheme. Green tints in the sky at dusk are not uncommon. Whether this sketch influenced the colour scheme of the Jack Pine studio painting is a different issue. Indeed, many of Thomson's sketches exhibit a greenish tint to the sky to a greater or lessor extent, e.g.:
Sunset

This sketch is thought to have been painted in 1915. (see the Tom Thomson Catalogue Raisonné entry for Sunset). It could be Grand Lake but probably not.
Birch by a Lake with Big Cloud

This sketch has the 'feel' of Grand Lake but it is not distinctive enough to be sure.
Northern Mist

It could be Grand Lake, but it could be a lot of other places as well.
Nocturne

This sketch is thought to have been painted in 1915. (see the Tom Thomson Catalogue Raisonné entry for Nocturne) However, we have an idea for this one on Grand Lake that we need to check out.
Birches

This view is suggestive of Grand Lake but is not distinctive enough to be sure. But perhaps it is near that of Bateaux (based on the point coming in from the left on the mid distant shore.)