B737 Undifferentiated or Other Model
Ground Event / Encounter Other / Unknown
General Maintenance Action
Airport; Weather
When we arrived weather conditions were a wintery blizzard; snow; blowing snow and very strong winds.  (NW 20+ gusting 30-40).  All taxiways and ramps were very icy.  We were assigned a gate; however the ground crew was having difficulties pushing a B737 off that gate due to the slippery ramp.  We waited for nearly an hour before we were assigned another gate.  We slowly entered the ramp area; parked the aircraft and set the parking brake.  We completed the Parking Checklist and kept the parking brake engaged.  The ramp triple chocked the the wheels (nose and 2 mains).  As deplaning began; I walked out onto the jet bridge.  As I was standing there with the gate agent and several passengers were deplaning; we witnessed the aircraft weather vane causing the nose to move right approximately 5-8 FT.  This caused a large (5 foot+ gap) between the aircraft boarding door and the jet bridge.  The flight attendants were able to stop the passengers from deplaning before anyone fell through the gap.  Looking down through the gap I could see the skid marks on the ice/snow where the nose gear had slid. It took some time; but to rectify the situation the ramp sprayed de-icing fluid around the nose wheel to provide some lateral friction.  They also attached the push tractor and tow bar to the aircraft.  There was no damage observed anywhere on the aircraft and we were not aware of any contact the aircraft or engines made with anything on the ground.  The gate agent was able to move the jetway up to the aircraft again and complete the deplaning process.
B737 First Officer describes an incident at the gate after landing and taxiing in during blizzard conditions with high winds. After gate arrival with passengers deplaning; and parking brakes set and all wheels chocked; the nose of the aircraft suddenly moves away from the jet bridge as the aircraft weather vanes in a strong gust of wind.