Date: 202007
Local time of day: 1201-1800
Location: ZZZ.TRACON, US
Flight conditions: Mixed
Weather elements / visibility: 10
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Communication Breakdown; Distraction; Situational Awareness
Second reporter function: Pilot Flying; Captain
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; Human Factors; Procedure; Weather
Primary problem: Human Factors

Narrative: We were vectored off the STAR to follow another aircraft that was deviating around weather. We were then given direct ZZZZZ; not on the STAR; to cross at 12;000 ft. then direct ZZZZZ1; on the STAR; and DESCEND VIA the arrival. I noticed the aircraft leveling off at 12;000 ft. We were then given direct to ZZZZZ1 to cross at 12;000 ft. and descend via the Arrival. During the confirmation procedure; I noticed 12;000 ft. on the PFD and 12;000 ft. on the FMS for ZZZZZ1; but I associated the bottom altitude of 11;000 ft. with descend via instruction instead of the current instruction of crossing the fix at 12;000 ft.; then descend via.Therefore; I confirmed the FMS for execution. I proceeded to review my STAR Approach Plate to confirm the bottom altitude on the arrival. ATC amended the instruction and cleared us to 11;000 ft. I was under the impression that we were complying with ATC instruction until the Captain queried if we missed a crossing restriction.


Second narrative: We were cleared direct to ZZZZZ and to cross ZZZZZ at 12;000 ft. Then we were cleared to ZZZZZ1 for the remainder of the Arrival. We were cleared to descend via the Arrival. There was weather around the ZZZZZ waypoint and another carrier in front of us wanted to deviate. They gave us a radar vector as well since we were behind them. Additionally; we were cleared to descend to 10;000 ft. We were getting radar vectored back towards ZZZZZ; and then we were cleared direct to cross ZZZZZ1 at 12;000 ft. We put direct to ZZZZZ1 in the FMS and both agreed and executed it. However; we were right at 12;000 ft. when I did that and the VNAV started to take it below the 12;000 ft. that we were cleared at ZZZZZ1; because on the arrival ZZZZZ1 has between 11;000 ft. and 12;000 ft. I tried to stop it but we went 200 ft. low and the Controller saw what happened and then cleared us to just cross ZZZZZ1 at 11;000 ft. The bottom line was we had a lot going on clearance wise and in the FMS and I just didn't quite catch the altitude quickly enough.


Synopsis: B737 reported descending below a crossing restriction during arrival.