UNEXPECTED LATE CHANGE FROM ATIS ADVERTISED VISUAL APCH RWY 22 TO AN ILS RWY 31C; CIRCLE TO LAND RWY 22 RESULTS IN BREAKDOWN IN CRM; SITUATIONAL AWARENESS AND; ULTIMATELY; BUSTING AN ALT RESTRICTION ON THE ARRIVAL.

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ON APCH TO MDW; WE WERE CLRED TO 'MAINTAIN 4000 FT UNTIL GLEAM; CLRED FOR THE ILS 31C CIRCLE 22L.' I CONTINUED IN NAV MODE AND INITIATED A PROFILE DSCNT TO 2300 FT; WHICH WAS THE ALT AT WHICH I WAS GOING TO CIRCLE; RATHER THAN ARMING APCH -- LAND; FROM WHICH I WOULD HAVE TO MANUALLY STOP THE DSCNT WHILE ON THE GS. THE ACFT BEGAN TO DSND; AND THE CAPT NOTED THAT; OVER GLEAM; WE WERE APPROX 3600 FT. WE RE-INTERCEPTED THE CORRECT PROFILE OVER RUNTS AND COMPLETED THE APCH. ATC NEVER MENTIONED THE DEV. THE MDW ATIS IS EXTREMELY WEAK; SO WE WERE UNABLE TO OBTAIN THE APCH IN USE UNTIL ONLY AROUND 75 MI FROM THE FIELD. THE APCH IN USE WAS ADVERTISED AS 'VISUAL 22L;' EVEN THOUGH FROM PAST EXPERIENCE; IN THIS CONFIGN WE COULD HAVE EXPECTED ILS RWY 31C CIRCLE RWY 22L. I BRIEFED THE RNAV RWY 22L AS A BACKUP FOR THE VISUAL. ONCE ON FREQ WITH CHICAGO APCH; WE WERE TOLD TO PROCEED DIRECT GLEAM AND TO EXPECT THE ILS RWY 31L CIRCLE RWY 22L. THE CAPT QUICKLY ENTERED DIRECT GLEAM IN THE FMS; AND THEN STRUNG THE APCH. WE THEN XFERRED CTLS AND I QUICKLY BRIEFED THE APCH. WHILE STRINGING THE APCH; WE DID NOT ENTER ANY TRANSITION BECAUSE WE WERE DIRECTLY INTERCEPTING FINAL. IN THIS SCENARIO; GLEAM DOES NOT SHOW UP ON THE APCH. WE THEREFORE MANUALLY REMOVED THE DISCONTINUITY BTWN GLEAM (WHERE WE WERE PROCEEDING) AND RUNTS. THIS SHOWED THE CORRECT WAYPOINTS FOR THE APCH; BUT THE MINIMUM ALT AT GLEAM (4000 FT) WAS NOT ENTERED. I DIDN'T NOTICE THAT THIS ALT WASN'T STRUNG. I DIDN'T LISTEN FULLY TO THE APCH CLRNC BECAUSE OF TASK SATURATION. WHEN I DIDN'T HEAR THE APCH CLRNC; I DIDN'T ASK TO REVIEW IT WITH THE CAPT. HE DIDN'T NOTICE THE PROFILE DSCNT TOOK US BELOW 4000 FT UNTIL WE WERE 400 FT LOW. BOTH OF OUR MISTAKES; AND LACK OF COM LED TO THIS DEV. WE BOTH KNEW THE ARPT; AND THAT THE APCH WE HEARD ON THE ATIS WAS ATYPICAL FOR THE CONDITIONS. WE SHOULD HAVE PREPARED FOR WHAT WE REALLY EXPECTED. WHEN BUILDING AN APCH FROM SCRATCH; EXTRA CARE SHOULD BE TAKEN TO MAKE SURE IT AGREES WITH WHAT IS ON THE PLATE. FINALLY; RUSHING AN APCH BRIEFING; ESPECIALLY WHEN EXECUTING AN UNUSUAL APCH LIKE THIS; SHOULD ALWAYS RAISE A RED FLAG.