definitely some differences here even with minor changes in elevation. 32-33F down towards Mass Ave (Spring Valley). 37-39F up closer to Tenleytown / Ft Reno (highest point in DC).
how far do most folks have their stations off the ground? Some of the others in my immediate area are 33-34, but I'm at 38. However, my station is about 10' off the ground.
around Tysons and across the river into upper NW DC is when you hit around 400+ feet in elevation (from Tenleytown we have a clear view of the Tysons "skyline" and can see Reston pretty well), so I'd imagine that is where that first jump is.