It was another rough day on Wall Street... the Dow dropped more than 300 points, slipping below the ten-thousand level for the first time since October. An increase in profit warnings from big companies is one reason the market is down. Northwest Airlines, for example, announced today it expects to lose up to 150 (M)million dollars in the quarter ending March 31st. But the local impact of the gloom on Wall Street reaches far beyond poor earnings for one company. Economist Sung Won Sohn says Minnesota's economy is still relatively strong. But bad news on Wall Street can serve as a warning of tough times ahead: