The NYPD seems poised to release an avalanche of punishment on some snowball fighters ... announcing they're investigating an incident after officers were pelted with snow.

New York City Police Commissioner Jessica S. Tisch announced cops are looking into a video taken in Washington Square Park Monday ... which shows officers walking through a huge crowd of people and being bombarded with snowballs.

Check out the clip ... the officers are hit in their faces, backs and heads as they march out of the park, remaining surprisingly calm despite the hail of frozen projectiles.

Later on, however, an officer surrounded by individuals pulled out pepper spray to send them scrambling ... taking the confrontation to a higher level.

Commissioner Tisch calls all the behavior exhibited in these videos both "disgraceful" and "criminal." The investigation remains ongoing.

Basically, this park situation snowballed quickly ... and may result in arrests. Stay tuned ...