Av Jones was out running down the canal on Thursday when she had a close encounter with a black snake.
She took to social media after her ordeal to warn others about the incident.
She urged others to keep an eye out when walking or running along the stretch of canal near the industrial estate and the Flash Leisure Centre. Ms Jones, writing on Facebook, said: “Just to let the runners and walkers know that I saw a snake on the canal leading out of Welshpool by the flash.
“I went for a run at 11.30am today As I was running back under the first bridge you get to, a very large and long all-black snake launched at my leg.
“Luckily, I jumped high enough that the snake brushed passed my leg and missed biting me.
“Then ran for my life, all dramatic. Just watch out for your dogs and legs if you’re going up there today.
“Biggest snake I’ve ever come across in the wild.”
Grass snakes after often sited in Mid Wales, however, earlier this year in North Wales a venomous snake was spotted on a beach on Abersoch.
The adder was spotted by a woman on the North Wales beach, and the previous summer four children were bit by venomous adders near beaches in Gwynedd.
Ms Jones believes the creature that tried to stop her run was a black adder.
She said: “I think, personally, I startled the snake as I came very fast at it from under the bridge.
“But I’ve never seen such a large snake in the wild before. That’s why I thought I should warn people, especially with little dogs or children. It looked like a black adder but it was way bigger than the typical one in the UK.”