Is there anyway to broker a truce between these two warring groups?

yes, but only temporarily

go through the Main Quest, you will reach a quest called "Season Unending"

Given that both has core goals that are mutually exclusive, I don't think there is much chance of any lengthy truce. A core Stormcloak tenant is to free Skyrim from the Empire's rule. A core tenant of the Empire's policy is to try to keep it all together while they try to rebuild to face the Domininon a second time.

As others said, the warring factions will ceasefire temporarily so you can deal with the dragons, then they'll get back to the fighting once that threat is gone. But no, they won't stop fighting until one side is completely destroyed.

They're never really fighting in game to begin with. Not untill the Dragonborn takes a side.

Except for the occasional skirmish you see as a random encounter.

I can honestly say I've never seen that before. I've seen random Imperial patrols escorting Stormcloak prisoners on the roads, however. That's how I know there's even a civil war. Without them, at least in my game, it'd be very odd that everyone's talking about a civil war, but there's little to nothing to indicate as such.