A B737-300 FLC TAKES EVASIVE ACTION CLB IN RESPONSE TO A GPWS COMMAND OF 'TERRAIN CLB.' FLT WAS AT THE ESTABLISHED ATC MVA ALT OF 6300 FT 3 MI NW OF SAMIE INTXN; ON APCH TO ILS RWY 14 AT MFR; OR.

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BEING VECTORED TO THE LOC; ATC DSNDED US TO 6000 FT MSL; AND TURNED US ON A HEADING TOWARDS SAMIE INTXN. WE WERE AT 180 KTS; FLAPS 10 DEGS; AUTOPLT ENGAGED (FO'S LEG). FO WAS IN TERRAIN MODE AND I WAS IN WX MODE. THE MSA FOR THAT SECTOR WAS 6300 FT MSL. WE WERE APPROX 3 NM NW OF SAMIE WHEN WE STARTED PICKING UP LIGHT GREEN ON THE TERRAIN MAP. WE WERE ON AN EXTENDED VECTOR DUE TO DEPARTING TFC ON RWY 32. WE DISCUSSED THE TERRAIN IN THE AREA AND AS THIS WAS HAPPENING; ATC GAVE US A TURN TO INTERCEPT THE LOC. IN THE MIDDLE OF HIS INSTRUCTIONS WE RECEIVED A 'TERRAIN' AND 'CLB' COMMAND FROM THE GPWS. FO COMPLIED AND I TOLD ATC; THAT WE WERE MANEUVERING TO A GPWS COMMAND. HE HAD US CLB TO 7000 FT MSL AND TURNED US TO REINTERCEPT THE LOC. WE CONTINUED THE APCH AND HAD A SUCCESSFUL LNDG TO MFR. THE APCH CHART STEP DOWN BEYOND SAMIE IS 6300 FT MSL. WE DISCUSSED THE FACT THAT WE WERE BELOW THAT (I ASSUMED WE WERE THE MVA) AND WE SAW ONLY GREEN ON THE TERRAIN MAP. AFTER THE APCH WE ASKED ATC WHAT IS THE MVA FOR THAT SECTOR. WE WERE TOLD 6000 FT MSL. THE CTLR STATED THERE IS AN AREA OF STEEP RISING TERRAIN WHERE WE WERE AND SOMETIMES ACFT WILL GET A GPWS WARNING. WHILE WE EXECUTED THE TERRAIN AVOIDANCE MANEUVER AND APCH SUCCESSFULLY; AN EARLIER INQUIRY TO ATC MAY HAVE HAD THE CTLR TURN US EARLIER. (WE CONFERRED WITH ATC ON THE GND AND THEY SEEMED A BIT NONCHALANT ABOUT THE WHOLE THING.)