Well if it's one of those SWFE deals, H7 might be warm, so I would look a little higher. Unfortunately many sites don't show 600mb, so you'd have to interpolate between 700 and 500. 850mb level usually is a good way to see if you have strong inflow and warm air advection. Many times that level is below the ideal snow growth area, unless it's very cold out. Sometimes just north of the 850mb warm front has heavy precip.