Why is it tumála, not *tumólo* etc.?

A simple question: why is ‘tomorrow’ pronounced tumála in Chinook Jargon? That’s a closer match for American English, isn’t it?

Image credit: Cannonball Read

We might suppose something more like British English was more common in the Pacific Northwest, in the earliest, formative decades of CJ.

The British dominated the main non-Indigenous economy, the fur trade.

In a British accent, you have [tumóro].

The earliest Jargon word lists do appear to vary between a stressed “á” and a stressed “ó” in this word. (To the extent that we can infer any one pronunciation from their spellings.)

So, do you figure we’ve wound up with the tumála pronunciation due to the eventual (1840’s+) US dominance in our region?