The most important part of this word, in my opinion, is that properly placed adumbration piques a reader's interest; it's what keeps them reading - they have a little hint of what may come and they want to know what it is!
Try thinking of it like this... The book is a mirror - as the reader reads it, they see only what's directly in front of them. But adumbration is what cracks the surface (just so slightly) to give them a glimpse of beyond what's displayed...
Here's an attempt I've given in my current work, Project Jane:
"On Monday, it began to rain. We were inundated with a steady downpour lasting for six days. The Bay water levels rose quickly and roads were closed from flooding. By Sunday the sun reappeared, but by then things were different - although looking back, I had no idea just how much had changed.Did I nail it? I don't know - where you tempted to keep reading? Did you see it though? In a seemingly innocent paragraph, I slipped the little hint in (italicized), and then came back to a normal tone as though I'd never given that little glimpse.
I didn’t really mind the rain. On the one good hand it meant we didn’t have to go outside for PE. On the other, better hand, it meant that..."
One thing to keep in mind is that you don't want to over do it with adumbration. If you slip too much in, a reader may get annoyed and distracted from the story with their frustration. KISS: Keep It Subtle, Silly.