David Yeates, 63, and wife Teresa, 58, made their plea in a week of intense activity in the hunt for the killer who left her body to be found in an icy lane on Christmas Day.
To recreate the weather conditions of that day, producers of a Crimewatch special retracing the landscape architect’s last steps are using Hollywood-style effects.
Fake snow has been shipped in to cover Longwood Lane, near Failand, Bristol, where Joanna’s body was found.
Gloucestershire-based firm Snowbusiness has worked on the Harry Potter films, Gladiator and The Day After Tomorrow. It will also provide dry foam to create falling snow, to be deposited by a specially-built £6,000 machine.
The Longwood Lane scene is one of six being reconstructed.
Joanna Yeates' last moments are being recreated
In other scenes 25-year-old Joanna – played by a young blonde lookalike – is seen in Tesco Express store buying a pizza.
Police now know that she did not eat the pizza. The box and its contents – missing since she vanished on December 17 – are still thought to be crucial to the investigation.
The actress is then filmed walking 250 yards to Joanna’s flat in Clifton. The film will be broadcast on BBC1 at 9pm next Wednesday.