HRRR: Top Soil and Surface Temperature

I'm looking at the surface temperature of the Great Salt Look and wondered if the top soil temperature or the surface temperature is what I should be looking at. Turns out, the top soil level and the lowest temperature level (surface temperature) are identical over water

Shown, difference between Soil Temperature (top soil level) and Surface Temperature:

As you can see, there is no difference between the surface temperature and top soil level temperature over the Great Salt Lake (thus, the white color over the lake area).

The same can not be said over mountainous areas, where there are the largest differences.