so...one round going up, another crashing down?
The problem is, to cover 1000 feet horizontally with a mostly vertical trajectory, it would take a ridiculously low angle, with the peak of the blast being the vertex, I'd say at maximum a 30o angle, and that's alot higher than I' actually expect it to be. Of course, no creature could possibly produce the pressure necessary to accomplish such a feat, but this is a magical beast after all, so I'd still say a good three rounds is appropriate.

And psionic devotee, It looks like you're using terminal velocity for a human, but what whould the terminal velocity be for a gigantic snowdrift? Not that it matters; 'enough to kill you' seems appropriate.

I am no longer a pixie! Hah! Beware VT, lest your position as a titan be swiftly usurped!