The currency markets have priced in a remain vote for the U.K.'s referendum on whether to leave the European Union, meaning Friday could be "very dramatic" if Britons vote to exit, currency investor Mark Astley said Thursday.
"The probability of remain has been factored into the pound to perhaps 85 or even 90 percent," the CEO of Millennium Global said in an interview with CNBC's "Power Lunch."
A Brexit vote "would be so unexpected that there could be a visceral reaction."
In fact, the pound could fall way below last week's low of $1.40 — into the $1.30s initially and perhaps even further down, Astley said.
The pound rose Thursday as Britons went to the polls to cast their Brexit vote. The currency hit a new high of $1.4943 against the dollar in midday trading Thursday, its highest level since Dec. 25, 2015. (Click here for the pound's latest movements)
Meanwhile, Britons are flocking to currency exchange locations to get transactions done before the outcome of the vote is announced.
Sakthi Ariaratnam, global director of Thomas Exchange, told "Power Lunch" that volume at its branches has jumped 40 percent and its online orders have increased 105 percent over the last week.
"People generally travel a lot during June, July, August — one of the busiest periods. And people in England book their holidays well in advance," he said.
"It only makes common sense to buy those currencies now."
If the Brexit vote wins, he said the pound could fall to slightly over $1.30, but noted it could possibly break the $1.30 support level.