The Powder River Basin, or PRB, is the cheapest coal region in the country. That's good news for miners focused on the area, like Peabody Energy (NYSE:BTU) and Cloud Peak Energy (NYSE:CLD). But weak coal prices continue to be a drag, which means third quarter results will continue to disappoint.

Already out
Peabody Energy reported earnings about a week ago and the results were mixed, at best. For example, the company was able to ship more coal from its Australian operations which, despite coal price weakness, helped the global coal miner turn a quarterly profit of a nickle a share from continuing operations.

Unfortunately, Peabody's U.S. operations didn't hold up as well, with both price weakness and reduced volumes. It's western coal volumes, which includes the PRB, were off 3% in the third quarter, year over year. Pricing was down a little over 7%. No wonder the $0.05 profit was lower than the $0.53 earned the prior year.

And it's worth noting that on a GAAP basis the company actually lost a dime a share. So the weak coal market continues to take its toll on this industry Goliath.

A better quarter
The weakness in Peabody's PRB business suggests that things aren't going to get much better for Cloud Peak, which is focused solely on the region. Peabody and Cloud Peak are two of the PRB's largest miners, which inherently means they need to lead the region toward lower volumes in the tough coal market.

For example, Cloud Peak expects domestic sales volumes to be flat to lower in 2013 compared to 2012. That, however, doesn't mean the company is set to post a quarterly loss. It came close to bleeding red ink in second quarter, however, when the miner saw earnings drop to just $0.08 a share.

That's awfully close to the dividing line, but was partially caused by maintenance work that should now be complete. Less volume during these maintenance outages left costs elevated and profits under pressure. Without that pressure, Cloud Peak is likely to see a sequential earnings improvement in the third quarter. The still weak thermal coal market, however, should lead to a year over year earnings drop.

10% is no solution
Another big miner with PRB operations set to post results this week is Alpha Natural Resources (NYSE:ANR). Similar to Peabody, Alpha is a fairly diversified miner, with operations in both thermal and met coal and a notable global presence. Only, like Cloud Peak, its mining operations are U.S. based.

That means that the weak Aussie dollar has made it difficult for Alpha's met coal to compete globally. Met made up about 45% of the top line in 2012. Plus, only about 10% of the company's thermal volume comes out of the ultra-cheap PRB. So even if demand remains strong for that basin's coal, Alpha isn't likely to see much benefit.

And the remainder of the company's business is in the eastern United States, an area that's experiencing big changes. The Illinois Basin, the second cheapest region in the country, is gaining share at the expense of Central Appalachian coal. So, the remaining 45% of Alpha's business is under pressure, too.

With 90% of its business in flux, Alpha's recent string of red ink—seven quarters long—should continue when it reports third quarter results later this week.

Still a standout
Even though Cloud Peak is likely to post lower year over year results, this PRB focused miner is still a standout performer. The results at both Peabody and Alpha prove this out. When reviewing the quarterly results, keep an eye on Cloud Peak's costs. And don't forget to watch its burgeoning export business, which should help to make up for lost U.S. sales both now and in the future.

Reuben Brewer has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.