A store clerk in the TV section of a new Walmart in San Salvador, El Salvador.

Walmart's surprising positive sales momentum is just getting started, according to Barclays.

The firm reinstated coverage on Walmart shares with an overweight rating, predicting the retailer's investments in improving its store experience will pay dividends.

"We believe that Walmart will be able to sustain comp gains over peers going forward," analyst Karen Short said in a note to clients Tuesday. "We believe this is a function of a stronger assortment, improved quality of fresh products, goals for stores to be 'clean, fast, and friendly,' wage increases [etc.]"

Walmart shares rose 1.5 percent Wednesday.

Walmart reported significantly better than expected sales numbers last month.

The retailer's shares closed up 9.3 percent on Aug. 16 after it posted its highest domestic same-store sales growth in more than 10 years for its second quarter. Walmart reported an increase of 4.5 percent versus the Thomson Reuters estimate of 2.4 percent.

Short initiated her price target at $110 for Walmart shares, representing 15 percent upside to Tuesday's close.

She said same store sale results have outperformed the average of its industry peers by about 150 basis points over the last six quarters.

"Walmart has regained momentum as evidenced by 15 consecutive quarters of positive traffic growth," Short said. "We see further room for [the retailer's] investments to drive comps."

Walmart's stock is down 3.4 percent this year through Tuesday versus the S&P 500's 8.3 percent gain.

Barclays suspended coverage for Walmart shares on May 9 because the firm acted as a financial advisor in a transaction involving the retailer.