ACR MLG FLC LEVELED OFF AT THE WRONG ALT DUE TO INADVERTENTLY SETTING THE WRONG ALTIMETER SETTING DURING CHANGEOVER AT FL180 DURING DSCNT.

Narrative

WE HAD DSNDED TO 22000 FT ON OUR WAY TO BUF. CTR GAVE US A XING RESTRICTION TO 'CROSS 30 S OF BUF AT 11000 FT. ALTIMETER 30.51.' THE FO READ BACK THE XING RESTRICTION INCLUDING THE ALTIMETER SETTING. THE SETTING SEEMED HIGH; BUT I HAD PLANNED TO VERIFY IT WITH ATIS. WHEN WE DSNDED BELOW FL180 I LISTENED FOR THE ATIS; IT WAS OFF THE AIR BEING UPDATED. WE WERE SWITCHED TO BUF APCH AND I CHKED IN LEVEL AT 11000 FT. APCH QUESTIONED OUR ALT SAYING HE SHOWED WE WERE AT 10000 FT. HE GAVE US THE ALTIMETER SETTING BUT IT SEEMS THAT IT WAS 29.74?? I'M NOT SURE; BUT THERE WAS A LARGE DIFFERENCE. WE RESET OUR ALTIMETERS AND CONTINUED TO BUF. THE WX ON THIS DAY WAS AFFECTED BY A VERY POWERFUL COLD FRONT; AND WE HAD EXPERIENCED LARGE CHANGES IN PRESSURE EVERYWHERE WE HAD FLOWN. I AM SURE THIS IS NOT THE FIRST TIME EITHER A CTLR GAVE A WRONG ALTIMETER SETTING OR A PLT MISUNDERSTOOD; READ IT BACK AND THE CTLR MISSED IT. BOTH THE FO AND I REMEMBER READING IT BACK CLRLY. 1 SIMPLE SOLUTION WOULD BE TO ALLOW THE CURRENT ATIS TO BROADCAST UNTIL THE NEW ATIS IS READY TO REPLACE IT.