A man grabbed a 19-year-old woman from behind, threw her into a pile of snow between two parked cars and tried to rape her before a witness scared him off in East Harlem early Tuesday, police said.

The woman had just gotten out of a cab at about 4:30 a.m. on Madison Avenue when she was grabbed from behind.

Her attacker threw her between two parked cars and began slamming her head into the ice and snow, police said.

A witness who heard her screams called 911 and gave a detailed description of the man, police said. The witness then scared off the attacker, who fled but was stopped by police nearby and taken into custody.

The 34-year-old suspect is charged with attempted rape.