Updated from 11:41 a.m. Shares of Gander Mountain ( GMTN) were among the Nasdaq's losers Friday, falling 16.5% after the company trimmed guidance. The outdoor specialty retailer now expects pretax income of $2 million to $4 million, down from previous guidance of $8 million to $13 million. Sales are now expected to be between $640 million and $645 million. Previously, the company expected sales of $640 million to $670 million. The company also expects same-store sales to decline 2% to 3%. Previously, Gander had forecast a decline of 1% to 3%. Gander Mountain said that unseasonably warm weather forced discounting and hurt margins. The latest warning marks the second time in 10 weeks that Gander has reduced full-year guidance. On Nov. 9, Gander Mountain shed 25% of its value after it warned Wall Street that full-year results would be significantly below previous guidance. At the time, investors were expecting pretax income of $16 million to $21 million, sales of $675 million to $700 million and comp-store sales growth of 3% to 5%. Shares of Gander have fallen by more than 40% since going public in April. Shares traded down $1.86 to $9.43. Tesoro ( TSO) fell 2.5% after the company warned that fourth-quarter earnings would fall short of expectations. The independent refiner expects to earn 5 cents to 10 cents a share, which includes an after-tax charge of 10 cents a share. Analysts had been expecting earnings of 42 cents a share. Results were hurt by operational problems at its Hawaii refinery and weaker margins in December. Shares traded down 76 cents to $29.55. Shares of Kennametal ( KMT) rose 3.5% after the Latrobe, Pa., toolmaker raised its second-quarter earnings outlook. The company now expects earnings of 74 cents a share on sales of $550 million. Previously, the company had forecast earnings of 60 cents to 65 cents a share. Analysts had been expecting earnings of 66 cents a share on sales of $525.7 million. Broad end-market strength and gains in market share led to the revised outlook. Full results will be issued on Jan. 26. Shares traded up $1.65 to $48.80.