Question: Is the weather forcast available in any of the high camps on Normal route? Any particular radio frequencies?

Although I do not know of a specific radio frequency for weather forecasts while you're on the mountain, the link below will give you a forecast for weather at basecamp, at 5900 meters, and at the summit.

http://www.aconcaguanow.com/meteoviejo.php/

The same information is available on a dry erase board within the web cam owners' tent (Miguel?) at Plaza des Mulas while you are on the mountain.

Hope this helps

There is a camp ranger at Nido de Condores (18300 ft), and I'm pretty sure he can use radio to get the weather report from Mulas. I did not use this service, but I think others in the camp did.