Stock Quotes in this Article: ARTC, ECPG, NVDA, THRX

MADISON, Wis. (Stockpickr) -- Professional traders running mutual funds and hedge funds don't just look at a stock's price moves; they also track big changes in volume activity. Often when above-average volume moves into an equity, it precedes a large spike in volatility.

Major moves in volume can signal unusual activity, such as insider buying or selling -- or buying or selling by "superinvestors."

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Unusual volume can also be a major signal that hedge funds and momentum traders are piling into a stock ahead of a catalyst. These types of traders like to get in well before a large spike, so it's always a smart move to monitor unusual volume. That said, remember to combine trend and price action with unusual volume. Put them all together to help you decipher the next big trend for any stock.

With that in mind, let's take a look at several stocks rising on unusual volume today.

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Nvidia

Nvidia (NVDA) is engaged in creating the graphics chips used in personal computers that bring games and home movies to life. This stock is trading up 4% at $14.47 in recent trading.

Today's Volume: 14.06 million

Average Volume: 10.47 million

Volume % Change: 136%

Shares of NVDA are ripping higher today after the company reported results that beat Wall Street expectations.

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From a technical perspective, NVDA is gapping sharply higher here right above some near-term support at $13.50 with above-average volume. This move is quickly pushing shares of NVDA within range of triggering a major breakout trade. That trade will hit if NVDA manages to take out some past overhead resistance at $15.03 and then once it clears its 52-week high at $15.22 with high volume.

Traders should now look for long-biased trades in NVDA as long as it's trending above $14, and then once it sustains a move or close above those breakout levels with volume that hits near or above 10.47 million shares. If that breakout triggers soon, then NVDA will set up to re-test or possibly take out its next major overhead resistance levels at $16.69 to $18.

ArthroCare

ArthroCare (ARTC) is a multi-business medical device company that develops, manufactures and markets invasive surgical products. This stock is trading up 1.7% to $34.68 in recent trading.

Today's Volume: 159,000

Average Volume: 101,706

Volume % Change: 152%

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From a technical perspective, ARTC is bouncing modestly higher here back above its 50-day moving average at $34.66 with above-average volume. This stock recently formed a double bottom chart pattern at $32.76 to $32.89. Since that time, shares of ARTC have ripped higher, and the stock is now quickly moving within range of triggering a near-term breakout trade. That trade will hit if ARTC manages to take out some near-term overhead resistance levels at $35.18 to $35.35 with high volume.

Traders should now look for long-biased trades in ARTC as long as it's trending above its 50-day at $34.66 or above today's low of $34.30 and then once it sustains a move or close above those breakout levels with volume that hits near or above 101,706 shares. If that breakout triggers soon, then ARTC will set up to re-test or possibly take out its 52-week high at $36.99. Any high-volume move above $36.99 will then put $38 to $40 into range for shares of ARTC.

Theravance

Theravance (THRX) is a biopharmaceutical company with a pipeline of internally discovered product candidates and strategic collaborations with pharmaceutical. This stock is trading up 10.9% at $34.73 in recent trading.

Today's Volume: 3.19 million

Average Volume: 1.27 million

Volume % Change: 248%

Shares of THRX are soaring higher today after the company won U.S. approval for its once-daily drug Breo Ellipta to treat a lung disorder that is the third-leading cause of death.

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From a technical perspective, THRX is exploding higher here right off some near-term support at $31.20 with monster upside volume. This move has started to push shares of THRX into breakout territory, since the stock has flirted with some near-term overhead resistance at $35.10. This move also briefly pushed shares of THRX into new 52-week-high territory, which is bullish technical price action. At last check, THRX has hit an intraday high of $35.80 and volume is well above its three-month average action of 1.27 million shares.

Traders should now look for long-biased trades in THRX as long as it's trending above $35.10 and then once it sustains a move or close above its 52-week high at $35.80 with volume that hits near or above 1.27 million shares. If that breakout triggers soon, then THRX will set up to enter new 52-week high territory, which is bullish technical price action. Some possible upside targets off that move are $40 to $45 in the near future.

Encore Capital Group

Encore Capital Group (ECPG) provides debt management and recovery solutions for consumers and property owners across a broad range of assets. This stock closed is trading up 2.4% to $30.89 in recent trading.

Today's Volume: 340,000

Average Volume: 202,108

Volume % Change: 140%

Shares of ECPG are moving higher here after the company beat Wall Street EPS estimates by 7 cents per share, but missed on revenues.

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From a technical perspective, ECPG is spiking higher here right off some near-term support at $30 with above-average volume. This stock has been uptrending strong for the last month, with shares soaring higher from its low of $26.84 to its intraday high of $31.35. During that move, shares of ECPG have been consistently making higher lows and higher highs, which is bullish technical price action. That move has now pushed shares of ECPG back above both its 50-day and 200-day moving averages, and the stock is now moving within range of triggering a near-term breakout trade. That trade will hit if ECPG manages to take out some near-term overhead resistance at $30.80 to $31.67 with high volume.

Traders should now look for long-biased trades in ECPG as long as it's trending above $30 or its 50-day at $29.32, and then once it sustains a move or close above those breakout levels with volume that hits near or above 202,108 shares. If that breakout triggers soon, then ECPG will set up to re-test or possibly take out its 52-week high at $33.07. Any high-volume move above $33.07 to $33.16 will then put $35 to $38 into range for shares of ECPG.

To see more stocks rising on unusual volume, check out the Stocks Rising on Unusual Volume portfolio on Stockpickr.

-- Written by Roberto Pedone in Madison, Wis.

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At the time of publication, author had no positions in stocks mentioned.

Roberto Pedone, based out of Madison, Wis., is an independent trader who focuses on technical analysis for small- and large-cap stocks, options, futures, commodities and currencies. Roberto studied international business at the Milwaukee School of Engineering, and he spent a year overseas studying business in Lubeck, Germany. His work has appeared on financial outlets including CNBC.com and Forbes.com. You can follow Pedone on Twitter at www.twitter.com/zerosum24 or @zerosum24.