wa'leS is not an adverbial, as The Klingon Dictionary uses the term. It is a noun. The general rule is that phrases expressing times go before everything else in the basic sentence.
wa'leS QIt paqvetlh vIlaD I'll read that book slowly tomorrow. The wa'leS has to come first because it expresses a time. The QIt slowly has to come next, because adverbials come before the Object-Verb-Subject part of the sentence.