The euro plunged to an 11-year low on Thursday, after the European Central Bank announced that it would begin a 60-euro monthly asset purchasing program. But it could still have a ways to fall.

Brown Brothers Harriman global head of currency strategy Marc Chandler predicts that the euro, which fell as low as 1.1362 on Thursday after trading near 1.4000 in May, is heading below 1.0. That widely watched level is the point at which it will just take a single U.S. dollar to purchase a euro, a condition known in the currency markets as "parity."