Narrative:

Descending through 6300 ft to level at 6000 ft, got GPWS/egpws mode 4 warning. Too low terrain/too low gear, with associated aural and visual warns. Radio altimeters on both sides rapidly showed 700 ft. Escape maneuver initiated. Second warning occurred with radio altimeters descending to 200 ft. Warn lasted 5-10 seconds after positive climb establish WX was moderate to heavy snow in the descent for approximately 5 mins prior to incident. Engine and wing anti-ice were on. Landed at bwi without further incident. Pulled voice circuit breaker and contacted maintenance at ZZZ and dispatch to report incident. Callback conversation with reporter revealed the following information: the reporter stated the ground proximity system was the enhanced version and the reporter believes the radio altimeters were affected by the heavy snow. The reporter said both radio altimeter tape indications descended together 1000 FPM in the heavy snow. The reporter said when this incident was discussed with the flight manager it was revealed that 2 or 3 other similar events were reported.

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Original NASA ASRS Text

Title: A B757-200 ON DSCNT AT 6300 FT TO LEVEL AT 6000 FT IN MODERATE TO HVY SNOW EXPERIENCED A FALSE GND PROX #4 WARNING.

Narrative: DSNDING THROUGH 6300 FT TO LEVEL AT 6000 FT, GOT GPWS/EGPWS MODE 4 WARNING. TOO LOW TERRAIN/TOO LOW GEAR, WITH ASSOCIATED AURAL AND VISUAL WARNS. RADIO ALTIMETERS ON BOTH SIDES RAPIDLY SHOWED 700 FT. ESCAPE MANEUVER INITIATED. SECOND WARNING OCCURRED WITH RADIO ALTIMETERS DSNDING TO 200 FT. WARN LASTED 5-10 SECONDS AFTER POSITIVE CLB ESTABLISH WX WAS MODERATE TO HVY SNOW IN THE DSCNT FOR APPROX 5 MINS PRIOR TO INCIDENT. ENG AND WING ANTI-ICE WERE ON. LANDED AT BWI WITHOUT FURTHER INCIDENT. PULLED VOICE CIRCUIT BREAKER AND CONTACTED MAINT AT ZZZ AND DISPATCH TO RPT INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE GND PROX SYS WAS THE ENHANCED VERSION AND THE RPTR BELIEVES THE RADIO ALTIMETERS WERE AFFECTED BY THE HVY SNOW. THE RPTR SAID BOTH RADIO ALTIMETER TAPE INDICATIONS DSNDED TOGETHER 1000 FPM IN THE HVY SNOW. THE RPTR SAID WHEN THIS INCIDENT WAS DISCUSSED WITH THE FLT MGR IT WAS REVEALED THAT 2 OR 3 OTHER SIMILAR EVENTS WERE RPTED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.