Shares of Union Pacific (UNP) - Get Report ended May with an impressive gain. The stock closed yesterday 1.5% higher with the help of a nice bump in trade. This bullish action may signal the end of a deep pullback that began five weeks ago.

If Union Pacific can continue to attract aggressive buyers, a healthy rebound move could be on the way.

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A few days after Union Pacific's earnings-inspired breakout move on April 21, the stock stalled just below $90. By the final day of the month, a pullback was underway. Initially the stock held the first layer of support near the 200-day moving average, but after closing below $82, it was clear a much steeper selloff was in the cards. Union Pacific fell all the way down to the $80 area, giving back all of its post-earnings ramp and then some. For the next two weeks, the stock remained in a very narrow range just below its downward-sloping 200-day moving average. A solid jolt of volume would be needed to break the stock out of this bearish pattern. Tuesday's rally provided exactly what Union Pacific needed.

As a new month begins, Union Pacific is set up well for a fresh bull leg. In the near term investors should take a more positive view of the stock as the five week pullback comes to an end. The rally on Tuesday has left behind a very solid layer of support. Union Pacific is a low-risk buy between last week's high of $85.30 and the May low of $80.70. A close back below the May low would indicate more bottoming action is ahead. On the upside, a logical target as the rebound develops is the 2016 highs set last month near $90.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author was long UNP.