As I understand the definition of Tempo, the condition is expected to last less than one hour and is expected to agregate less than 50% of the period indicated and is expected to be temporary. Becmg is unnequivocal, the condition is to be treated as being present from the beginning of the time period indicated and is a permanent change. Prob is either 30% or 40% since, as I understand it, 50% becomes tempo.
Be that as it may and bearing in mind that sound judgement may lead you to not selecting an airfield that is prob30 or tempo below limits, I believe that you can legally use a div that is prob30 and/or tempo below limits. I just can't remeber where I learnt it.