THE PIPER PA-18, N3594P, WAS BEING USED TO TOW A BURKHART GROB FLUGZEUGBAU G103 TWIN ASTIR, N4246L. AT 0950 MST, THE WIND WAS REPORTED FROM 310 DEG AT 9 KTS. SINCE THE TERRAIN SLOPED DOWNHILL TO THE SOUTH, RWY 17R (COVERED WITH HARD PACKED SNOW) WAS BEING USED FOR TAKEOFF. THE GLIDER CLUB HAD A POLICY THAT ALL TAKEOFFS WOULD BE MADE TO THE SOUTH, BUT NO TAKEOFFS WERE PERMITTED IF THE TAILWIND EXCEEDS 20 KTS. THE TOW PLT REPORTED THAT DURING TAKEOFF, A QUARTERING REAR GUST OF WIND WAS ENCOUNTERED & FORCED THE ACFT BACK ONTO THE RWY. THE ACFT TOUCHED DOWN AT THE END OF THE RWY, ROLLED INTO SNOW & NOSED OVER. THE INSTRUCTOR PLT (CFI) IN THE GLIDER REPORTED THE GLIDER HAD JUST LIFTED OFF WHEN HE SAW THE TOW PLANE SETTLE TO THE GROUND & DISAPPEAR IN A CLOUD OF SNOW. THE GLIDER STUDENT RELEARSE THE TOW ROPE. THE GLIDER ENTERED THE CLOUD OF SNOW. WHEN IT EMERGED FROM THE CLOUD, THE GLIDER AIRCREW SAW THE INVERTED TOW PLANE IMMEDIATELY AHEAD. THE LEFT WING OF THE GLIDER HIT THE RIGHT MAIN GEAR OF THE TOW PLANE. TOW PLT EST GUSTS, 15 KTS.