Arch Resources (ARCH) appears an attractive pick given a noticeable improvement in the company's earnings outlook. The stock has been a strong performer lately, and the momentum might continue with analysts still raising their earnings estimates for the company.The rising trend in estimate revisions, which is a result of growing analyst optimism on the earnings prospects of this coal producer, should get reflected in its stock price. After all, empirical research shows a strong correlation between trends in earnings estimate revisions and near-term stock price movements. Our stock rating tool -- the Zacks Rank -- is principally built on this insight.The five-grade Zacks Rank system, which ranges from a Zacks Rank #1 (Strong Buy) to a Zacks Rank #5 (Strong Sell), has an impressive externally-audited track record of outperformance, with Zacks #1 Ranked stocks generating an average annual return of +25% since 2008.For Arch Resources, there has been strong agreement among the covering analysts in raising earnings estimates, which has helped push consensus estimates considerably higher for the next quarter and full year.The chart below shows the evolution of forward 12-month Zacks Consensus EPS estimate:12 Month EPSCurrent-Quarter Estimate RevisionsFor the current quarter, the company is expected to earn $1.57 per share, which is a change of +148.16% from the year-ago reported number.Over the last 30 days, one estimate has moved higher for Arch Resources compared to no negative revisions. As a result, the Zacks Consensus Estimate has increased 168.44%.Current-Year Estimate RevisionsFor the full year, the earnings estimate of $9.73 per share represents a change of +142.79% from the year-ago number.In terms of estimate revisions, the trend for the current year also appears quite encouraging for Arch Resources. Over the past month, two estimates have moved higher compared to no negative revisions, helping the consensus estimate increase 146.02%.Favorable Zacks RankThe promising estimate revisions have helped Arch Resources earn a Zacks Rank #1 (Strong Buy). The Zacks Rank is a tried-and-tested rating tool that helps investors effectively harness the power of earnings estimate revisions and make the right investment decision. You can see the complete list of today's Zacks #1 Rank (Strong Buy) stocks here.Our research shows that stocks with Zacks Rank #1 (Strong Buy) and 2 (Buy) significantly outperform the S&P 500.Bottom LineWhile strong estimate revisions for Arch Resources have attracted decent investments and pushed the stock 9.1% higher over the past four weeks, further upside may still be left in the stock. So, you may consider adding it to your portfolio right away. More Stock News: This Is Bigger than the iPhone! It could become the mother of all technological revolutions. Apple sold a mere 1 billion iPhones in 10 years but a new breakthrough is expected to generate more than 77 billion devices by 2025, creating a $1.3 trillion market. Zacks has just released a Special Report that spotlights this fast-emerging phenomenon and 4 tickers for taking advantage of it. If you don't buy now, you may kick yourself in 2022.Click here for the 4 trades >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Arch Resources Inc. (ARCH): Free Stock Analysis Report To read this article on Zacks.com click here.