ACFT CLRED TO DSND BELOW SECTOR MSA; 4900 FT. FLC NOTICED DISCREPANCY ON APCH PLATE; THEN VISUALLY SAW RIDGELINE JUST BEFORE RECEIVING A GPWS TERRAIN WARNING. THEY CLBED AND NOTIFIED ATC; WHO SAID THEIR PRESENT SECTOR MSA WAS 4000 FT.

Narrative

APPROX 20-25 NM NNW OF SWF WE WERE GIVEN A DSCNT TO 4000 FT. HEADING WAS BTWN 150-170 DEGS GOING DIRECT TO NEELY LOM FOR ILS RWY 9 TO SWF. AFTER LEVELING AT 4000 FT; I NOTICED; AND TOLD THE CAPT; THAT THE MSA N OF THE ARPT ON THE ILS RWY 9 APCH PLATE WAS 4900 FT. IT WAS VFR; NIGHT AND WE COULD SEE A RIDGELINE IN FRONT OF US. AS WE APCHED THE RIDGE WE GOT THE AURAL TERRAIN ALERT AND THE RED GPWS LIGHT. THE CAPT IMMEDIATELY CLBED TO 5000 FT. THE WARNING STOPPED PASSING THROUGH APPROX 4500 FT. AS THE CLB WAS STARTED THE LOWEST THAT I SAW ON THE RADAR ALTIMETER WAS 1700 FT. I TOLD APCH THAT WE HAD CLBED DUE TO THE TERRAIN ALERT AND HE SAID THAT MSA FOR THAT AREA WAS 4000 FT. I ASKED HIM ABOUT THE 4900 FT MSA ON THE APCH PLATE AND HE SAID THAT HE DID NOT KNOW ABOUT THAT BUT THAT THE MSA FOR WHERE WE WERE WAS 4000 FT BUT WE COULD STAY AT 5000 FT FOR NOW. WE CONTINUED AND MADE AN UNEVENTFUL APCH AND LNDG AT SWF. WHEN WE NOTICED THAT THE MSA ON OUR APCH PLATE WAS HIGHER THAN OUR ALT WE PROBABLY SHOULD HAVE QUESTIONED APCH OR CLBED.