[Closed] Road closures and getting through snow

I'm trying to make a case to persudae my mate to come up to this race in the Beacons. Looking at the traffic cameras on traffic-wales the A470 looks clear, but the A470 is closed.

The question is, if they close a road can you try and get through anyway? He as a 4x4 with semi knobbly tyres, and I have 2wd with winter tyres, so I fancy either of our chances. Is it legal to do this?