A321
Air Traffic Control Developmental
Confusion; Distraction; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
I was the D-Side at Sector XX/XY.  Aircraft were deviating south of a large cell of weather. Aircraft coming over to us from RXZ were just clipping our lower corner of our sector and deviating into RXZ airspace. We notified the Supervisor of the situation and he was trying to get a plan going with TMU for different routing.  I notified the R-Side of an overtake situation. We came up with a plan to descend the A321 to FL320. The sector was starting to get overloaded so the Supervisor had RXX split-out; while trying to split out the sector other coordination was need to be taken care of so I was doing so. Once the sector was split; I then moved to DXX; at this time the new R-Side saw the confliction and turn both aircraft and climbed one to FL350. The previous R-Side forgot to descend the A321 to FL320 while trying to split out a sector. It would of been better to staff an L-Side for 5-10 minutes while traffic calmed down and had an extra pair of eyes to help watch all the aircraft deviating. Trying to split the sector out was too much confusion. Also we should of had RXZ working most of the aircraft because they were deviating so far south that they were in RXZ airspace.
Enroute Controller described a loss of separation event claiming the ill timed spitting of the sectors was a contributing factor in the occurrence.