The firm said Friday that the S&P 500 could see a mid-year trough at 2,000—that's down around 20% from current levels and 41% from its all-time high. Goldman says it is using the Fed model, a Dividend Discount Model, and history to come to that bottom—and has already cut its EPS forecast twice in two weeks (the firm is now forecasting S&P 500 EPS will decline by 5%) .

For those like Randy Frederick, the vice president of trading and derivatives at Charles Schwab, markets could easily test the lows from December of 2018, which is 2,351 on the S&P. "We got relatively close [on Monday] but we didn’t get there," Frederick tells Fortune. But given that the S&P 500 hit around 2,400 in intraday trading on Monday, it's likely the index might test that support level soon—"50 points could evaporate in five minutes in this market," he says.

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