According to the DOT:
"Traffic signals with a flashing yellow arrow phase are used at intersections where there is an exclusive right- or left-turn lane with a protected green arrow, which allows motorists to turn while oncoming traffic is stopped. The signal changes from a green arrow to a solid yellow arrow, indicating that a red signal is coming and turning motorists should not enter the intersection. A red arrow is then displayed, allowing traffic from the oncoming direction to begin proceeding through the intersection. After opposing traffic gets the green phase, the turn arrow begins flashing yellow, indicating that turning vehicles must yield to oncoming traffic but may proceed when there is a safe gap in traffic. The signal then turns returns to a solid yellow arrow and then to a red arrow as traffic on the other road is allowed to proceed through the intersection." Read more at WGRZ.