Regional Jet 900 (CRJ900)
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Rejected Takeoff; Flight Crew Returned To Gate
Procedure; Weather; Human Factors
At the gate in ZZZ I observed that roughly 50% of the wings were covered with slush.  I notified the CA of this; and experienced difficulty persuading him that de-icing would be needed because from the cockpit he only observed rain at a temperature of 3*C.  He could not see the ice pellets bouncing off the plane and ground.  We were notified that an FAA inspector would be joining us in the cockpit for this flight; and at this point the CA was willing to de-ice; but was becoming very agitated.  By the time we were closing the door to pusback; the CA had begun explaining to the inspector that we would need to de-ice; and that we had a new de-ice procedure that the CA did not like; and had never received any training on using.  The CA made it clear to both the inspector and me that he didn't want to use the de-ice checklist because it didn't allow him discretion on engine/APU configuration and was (in his opinion) needlessly cumbersome.  While trying to make our way to the de-ice pad the CA attempted to convince the inspector that we should not use the checklist and instead just have the CA tell me what to do and when because the CA remembers the previous way of doing it very well; and preferred the old way.  Throughout the taxi to de-ice; and the taxi after de-ice to the runway both the inspector and I had to assert that following the checklist was the safest and smartest choice.  Multiple times in front of the inspector the CA told me to skip portions of the checklist; re-arrange the order; and shorten the wait times listed before moving forward (such as waiting 3 mins to turn on the packs); and I had to insist that the checklist be followed.  During all of this the CA became increasingly agitated.  We were able to complete the checklist; and received takeoff clearance.  Above 80 kts we received both LEFT and RIGHT COWL A/I caution messages and we aborted the takeoff.  We cleared the runway; stopped; ran the Immediate Action Items and QRH; and returned to the gate.  At that point I indicated that based on the difficulty with insisting on SOP compliance despite having an FAA inspector observing that operation; I could not continue to fly with this particular CA.The weather was a threat; and would've been at any airport.  In ZZZ this type of weather event is extremely rare and the lack of experience with de-icing at that airport makes it a much more significant threat.  Having an observer is a threat because crewmembers tend to divert attention to second-guessing every move that should be spent on the operation.  Having a CA unfamiliar with changes made to the checklists; and unwilling to comply is a threat. I believed I was ultimately able to maintain a safe and compliant operation; but I also believe that I may not have had such success if the FAA inspector had not been there to back me up.  Continuing to insist on doing the correct thing is important.
CRJ900 First Officer reported that they rejected takeoff due to a cowl anti-ice warning.