When compared to historical records, the period ending in late April was fairly calm in terms of the amount of tornadoes produced. However, that changed in a big way over the past two weeks.
The Moore, Oklahoma, tornado was towards the beginning of a two-week period of massive severe weather outbreaks. During that week, 84 tornadoes occurred between May 18 and May 24. While 29 tornadoes occurred on Monday (including Moore), 32 tornadoes struck Tuesday. In addition to tornadoes, high amounts of wind damage also occurred. When you add up each report of severe weather (tornado, wind damage, large hail), 1572 instances of severe weather happened in just that seven day period.
During this past week, Monday through Friday produced 114 tornadoes, including ones that struck Oklahoma yet again on Friday. The pattern of high severe weather reports finally broke on Saturday, with zero tornadoes reported.
The set-up that produced all the severe weather was in place more many days. Hot & humid air moved up from the Gulf of Mexico into the southern Plains at the same time hot & dry air moved in from the west, and colder & dry air moved in from the north & northwest. A powerful jet stream sliced through all of this, allowing strong winds and rotation to be utilized by the storms. This pattern finally broke down and weakened considerably by June 1.