A commercial fixed wing aircraft experienced a GPWS TERRAIN warning on a visual approach to BHM.

Narrative

On the visual approach to Runway 36 at BHM; as we passed over a ridge (radar altimeter had just called 500 feet over what appeared to be the highest point) approximately 3 miles from the airport; the GPWS alert 'Terrain; Terrain' followed by 'Whoop; Whoop; Pull Up' briefly sounded. As we had acquired the airport 15 miles out and at this point had a clear straight line view to the touch down zone of Runway 36; we were a bit confused. Before I (as the flying pilot) could initiate an escape maneuver; the alarm stopped (only lasted 2 seconds). I leveled off briefly and; in the absence of further GPWS callouts; continued the visual descent to Runway 36. As we were on a visual approach; we had loaded the visual approach into the GPS. Additionally; we had enabled the snowflake. Although aware that the snowflake does not provide terrain separation; we typically attempt to follow the snowflake so as to descend at an appropriate descent rate. As we approached Runway 36; I had been maneuvering the aircraft to keep the flight path well clear of the ridge. As a backup; I also attempted to keep the snowflake centered. Apparently; this is one of those situations where following the snowflake will cause the aircraft to penetrate the GPWS terrain parameters for this runway.