ACR FLT CREW DESCENDS EARLY TO 5000 FEET AFTER PROCEDURE TURN ON ILS 14 AT MFR CAUSING GPWS TO ACTIVATE.

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WE WERE DSNDING INTO MEDFORD; OR (MFR); EXPECTING A VISUAL APCH TO RWY 32. ZSE HAD GIVEN US A DSCNT TO 9000 FT. AT 9000 FT; WE LOST CONTACT WITH THE ARPT. AT THAT TIME; ZSE INSTRUCTED US TO PROCEED DIRECT TO THE ROGUE VALLEY VOR (OED) AND UPON REACHING THE VOR; WE WERE CLRED FOR THE ILS RWY 14 APCH. WE SET UP THE FMS FOR THE APCH AND BEGAN TO TRACK THE LOC OUTBOUND FOR THE PROC TURN. ZSE TOLD US THAT RADAR SVC WAS TERMINATED; ADVISORY FREQ (CTAF) WAS TO BE CONTACTED AND THAT WE WERE TO CALL THEM ON THE GND WITH OUR FLT PLAN CANCELLATION. AS WE TRACKED THE LOC OUTBOUND; WE DSNDED TO 6300 FT AS DEPICTED ON THE CHART. UPON TURNING INBOUND ON THE LOC; WE BEGAN A DSCNT TO 5000 FT. AS WE WERE DSNDING; I REALIZED THAT WE WERE NOT AT THE PROPER LOCATION ON THE APCH TO BE AT 5000 FT. SHORTLY AFTER; THE GPWS INDICATED A WARNING TO PULL UP. THE AUTOPLT WAS DISCONNECTED AND AN IMMEDIATE CLB WAS INITIATED. AT THAT TIME; WE ACQUIRED THE RWY VISUALLY. WE CONTINUED THE APCH TO THE RWY REMAINING ON THE LOC AND GS. WE LANDED WITHOUT FURTHER INCIDENT. I BELIEVE THAT THE CIRCUMSTANCES THAT CONTRIBUTED TO THIS EVENT ARE AS FOLLOWS. AT THE TIME THIS EVENT OCCURRED; WE HAD FLOWN APPROX 6 HRS AND 45 MINS AND HAD BEEN ON DUTY FOR APPROX 10 HRS. THE LCL TIME WAS APPROX XC00. WE DEPARTED ZZZ AT XA51 LCL AND HAD JUST FLOWN FOR 2 HRS. I BELIEVE THAT OUR LEVEL OF AWARENESS AND CONCENTRATION WAS NOT AS GOOD AS IT WOULD HAVE BEEN EARLIER IN THE NIGHT. I BELIEVE THAT IF CREWS ARE TO BE FLYING THIS LATE INTO THE NIGHT; THEN SCHEDULES SHOULD BE CREATED THAT WOULD MINIMIZE FLYING PRIOR TO STARTING SUCH A LATE FLT.