The road between Cynwyl Elfed and Carmarthen has been closed following a landslide, which also brought down some trees.
Diversions are in place with traffic being sent over the hill through Blaenycoed and Trevaughan.
It is expected that the road will remain closed overnight.
Local residents have said that this is one of a number of incidents in recent months along the road and that something needs to be done to clear dangerous trees along the route. One local farmer said that the contractors were at the very same spot clearing a tree, which had fallen last week. He said that contractors had offered to clear the area of dangerous trees but had been told to clear just the tree that had fallen.
An amber warning – the second highest level – has been issued for wind in parts of Wales today, Saturday (Aug 5).
Gusts of 40-50 mph are expected with gusts in some areas reaching as high as 70mph.
Travel disruption is expected as rail, air and ferry services may be affected, and roads and bridges may close.
The warning for west Wales and parts of the south runs from 11:00 to 19:00 BST.
It covers Swansea, Carmarthenshire and Pembrokeshire.
