A319 CREW HAD AN EGPWS 'TERRAIN TERRAIN' WARNING ON A VISUAL APCH TO RWY 29 AT MSO.

Report 1 | Narrative: SPOKANE APCH ISSUED VECTORS TO VISUAL APCH FOR RWY 29 AT MSO. WHILE AT 9000 FT MSL HANDED OFF TO MSO TWR. CLRED TO LAND STRAIGHT IN RWY 29. RECEIVED SINGLE PHRASE 'TERRAIN-TERRAIN' WHILE OVER THE RIDGE TO THE E OF MSO; AND ALSO S OF CTRLINE OVER A LOW SECTION ('SADDLE'). EPGWS WITH TERRAIN SELECTED TO NAV DISPLAY; DID NOT INDICATE 'AMBER TERRAIN' AT THIS POINT. VISUALLY; WE WERE SAFE. WARNING WAS BRIEF/MOMENTARY. NO CORRECTIVE MANEUVERING NEEDED; AS THE VALLEY WAS VISIBLE. PROCEEDED TO LAND WITH NORMAL DSCNT RATE. SUPPLEMENTAL INFO FROM ACN 629470: DSNDING FOR VISUAL APCH RWY 29 MSO; WE RECEIVED A 'TERRAIN; TERRAIN' GPWS WARNING.

VISUAL CONDITIONS AT THE TIME WITH TERRAIN CLRNC ASSURED; SO NO CORRECTIVE ACTION NECESSARY. PASSING OVER RIDGELINE WHEN WARNING OCCURRED SO WARNING MAY HAVE BEEN ASSOCIATED WITH SUDDEN RADIO ALTIMETER SENSING THE TERRAIN.

Report 1 | Synopsis: A319 CREW HAD AN EGPWS 'TERRAIN TERRAIN' WARNING ON A VISUAL APCH TO RWY 29 AT MSO.