During ground school, I was taught to use the standard lapse rate to interpolate temps aloft. Since temps are not given for 3000', is it better to interpolate between the surface temperature and the 6000' temperature, or interpolate down from 6000' using the lapse rate? I'm interested to know the justification behind the answer. Similarly, for altitudes below 3000', is it reasonable to interpolate between the wind vector given by the winds aloft forecast, and the surface wind given by the relevant TAF? I notice that foreflight does not account for winds aloft for low altitudes (say, 2000'); why is this so?