The 19-year-old speedster was included in the Wales Under-20s squad for the Junior World Championships in New Zealand, only to be pulled out to feature in the May 30 trial match that precedes the naming of the 31-man squad that Warren Gatland will take to tackle the Springboks.
Amos will line up for the Probables alongside the likes of Alex Cuthbert, George North and Liam Williams with it appearing that he is well placed to add to the one cap he won against Tonga last autumn.
But despite admitting to being impressed with Amos in the RaboDirect PRO12 this season, Howley is not about to make any promises to the teenager.
"It was only sensible that he was named in the initial Under-20s but we guessed this day would come," Howley, who will be in charge of the Probables, told the South Wales Argus.
"I've spoken to Hallam and told him there are no guarantees about South Africa; ultimately it's down to his performance against the Possibles.
"Hallam was involved with us in the autumn and probably would have been in the Six Nations squad were it not for injury.
"He is an immense talent and I've watched him several times recently for the Dragons; I felt he played particularly well, as all of the back three did, against the Ospreys.
"Hallam has an eye for the counter-attack, the ability to beat the first defender."
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