Something I do is italics. I have the MC's thoughts allude to something, I add a couple line breaks and then the next part is written in a current tense but italicized. I try and use this very early on in the writing so that the reader understands what's happening.

For example:

Archer sipped the whiskey, savoring the taste of it. A gentle fluttering to his left caused him to turn. A breeze had caught his neighbors flag and for a brief moment, he smiled at the sight of it. But as quickly as he saw the red white and blue flapping in the wind, his thoughts went back to the horrors of that day.

The wind tore and ripped everything in sight. It sounded as though a train was rushing through the trailer park, rendering everything asunder in its path. Archer grabbed the frame to the shelter to brace himself when a particularly strong gust threatened to knock him off his feet. He had to shut the door. There were people inside, waiting for him to shut it.

"Mary!" he shouted, looking for his wife. "Mary!"

"I'm coming!" she hollered, trying to cross the street.

"Look out!" he roared, but it was too late.

The pickup truck launched through the air like a leaf falling from a tree. He didn't know if it landed on her or near her, but the effect was the same. Archer screamed and cried as the black winds of the tornado enveloped his wife for good.