The search for Peter Bohan has entered its fourth day in Drumlish.
The 79 year old was last seen leaving his property at Cloonellon on the Newtownforbes Road on Sunday afternoon.
Intensive searches of the surrounding area have been conducted over the last three days by Longford Civil Defense, Gardaí and locals.
A major public search was called for yesterday by local Councillor Padraig Brady, with that operation set to kick off this morning.
The search will include Gardaí and the Civil Defense, with authorities allowing over 18s only and those who are in good health to take part.
A safety briefing will be held for volunteers within the next hour at Manning's Yard in Drumlish.
Searches are requested to wear high vis and suitable footwear and to bring water and a stick for searching vegetation.
Volunteers must sign in and out with local Civil Defense, with local motorists advised to be careful with extra footfall expected on local roads over the course of the day.
Anyone who was in the area on Sunday and who has dash cam footage are asked to make it available to Longford Gardaí.
