Express, Inc. (NYSE: EXPR), a specialty retail apparel chain, issued a harsh downward revision Tuesday, slashing its third-quarter earnings forecast well below Wall Street’s already lowered expectations because of fewer shoppers in September and heavy discounting, triggering a steep sell-off.

The gloomy profit warning sent Express, Inc. (NYSE: EXPR) shares plunging 20.98 percent, or $3.15, to a new 52-week low of $11.86 a share on above-average volume. Even before Tuesday’s tumble the company’s shares had lost 5 percent of their value since returning to the public markets in May 2010 and about 25 percent so far in 2012.

Express has been looking to re-craft its offerings after an earlier strategy of selling pricier knit sweaters did not reap the desired results. In just five months’ time, Express lowered its outlook three times. No wonder investors are spooked.

The chain experienced "an abrupt change in traffic" last month and stepped up promotions, said Chief Executive Officer Michael Weiss in a statement. He said that customer traffic trends improved last week.

The Columbus, Ohio-based company, which sells casual and work clothing to 20- to 30-year-old men and women, said higher promotional activity to reduce inventory levels also contributed to lowered estimates.

The young-adult clothing retailer said it now expects to earn 16 cents to 20 cents a share in the current quarter, down from 27 cents to 32 cents and well below the Street’s consensus view of 29 cents.

Express’s net income projection was slashed to $14 million to $17 million, compared with $23 million to $28 million previously.

The company, which will report its full third-quarter results during the week of Nov. 26, expects third-quarter comparable sales to decline in the mid-single-digit range.

Express reported in August its fiscal second-quarter earnings rose 26 percent, though sales grew slower than expected amid increased promotional activity in the latter part of the period.