Thunderstorm Wind in Bryan County, Oklahoma

Trees and power lines were blown down at multiple locations in the community of Achille. The event time is estimated from radar observations.

The first of a multi-day series of severe thunderstorm events occurred across central and eastern Oklahoma from the afternoon of the 17th into the early morning hours of the 18th. This period was marked by a transition in the synoptic regime, as persistent upper-level ridging -- which had supported a stretch of quiet mid-May weather -- began to break down, giving way to broad troughing across the Western United States.

The initial round of severe convection on the 17th featured a notable splitting supercell thunderstorm. The right-split storm tracked across south-central and southeastern Oklahoma, producing intermittent reports of large hail and damaging winds, along with a tornado north of Pauls Valley, OK. Meanwhile, the left-split thunderstorm moved into the southwestern and western Oklahoma City Metropolitan Area, producing reports of large to very large hail. Additional severe thunderstorms moved across the Red River into southeastern Oklahoma during the evening, producing a few reports of thunderstorm wind damage.

A second more expansive round of severe thunderstorms emerged after sunset across west-central into central Oklahoma, as greater deep-layer ascent overspread the region. This activity produced multiple reports of large to very large hail, particularly across the greater Oklahoma City Metropolitan area, continuing into the early morning hours of the 18th.