Nov 22 (Reuters) -U.S. cotton futures mostly unchanged on Wednesday as investors rolled over from the front-month contract ahead of Thursday's Thanksgiving holiday and braced for weekly export sales data anticipated later this week.

* The second-month March contract CTc2 was flat at 80.59 cents per lb at 1:35 pm ET (1835 GMT).

* The dollar index .DXY was up 0.5%, making cotton less attractive to buyers holding other currencies. USD/

* "They're going to trade in an abbreviated session on Friday, so a lot of the traders have rolled their positions and they have vacated the market," said Keith Brown, principal at cotton broker Keith Brown and Co, in Georgia.

* "We'll get deliveries on Friday for the December contract, we'll see what export sales are doing and then the March cotton will take the helm."

* The U.S. Department of Agriculture's (USDA) weekly export sales report is due on Friday, delayed by a day because of Thursday's holiday. EXP/COT

* The USDA's weekly crop progress report released on Monday showed 77% of the cotton crop had been harvested in the week ended Nov. 19, compared with 67% in the prior week.

* In the grain market, Chicago wheat gained more than 1% as a Russian attack on a Ukrainian port continued to stoke worries over trade in the Black Sea, an integral route for the global grain market. Soybeans declined, while corn ticked up. GRA/

* Cotton's planted area in Brazil was estimated to rise 14.9% year-on-year to 1.94 million hectares, while output was forecast to jump 16.4% to an all-time high of 3.74 million tons, agribusiness consultancy Agroconsult said on Wednesday.

Reporting by Sherin Elizabeth Varghese in Bengaluru; Editing by Shilpi Majumdar