The A44 from Llandegley to Forest Inn bends is currently blocked due to an accident.
Officers are currently dealing with the accident, and are advising people to use alternative routes.
A spokesperson for Llandrindod, Builth, Rhayader, Presteigne and Knighton Police has said: "The road is currently blocked, please avoid the area and take an alternative route.
"However, due to the current snow and road conditions, we recommend you only travel if completely necessary."