EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors; Weather
During descent; after leveling at ATC assigned 12;000 FT; ATC queried about our assigned altitude. Pilot not flying indicated 12;000 FT assigned and asked what ATC was showing and asked for current altimeter. ATC said 29.06 was the destination altimeter and assigned 12;000 FT. Had mistakenly read and set 29.56 on ATIS causing lower altitude (lighting conditions low light; with turbulence and icing). Reset altimeters to correct 29.06 and made immediate climb to 12;000 FT assigned altitude. No apparent problems with ATC or other aircraft. Continued to our filed destination without incident.
An EMB145 crew did not set the correct barometric altimeter setting and realized; after ATC asked them to verify their altitude; that they were 500 FT low.