RARELY SEEN Helo Aerodynamic Dashed Linear Contrail & Rotor Vortices: Blackhawk & CH-47 Chinook

All aviation engines that burn hydrocarbon and produce heat will form contrails ... but very rarely seen in helicopters from the ground unless the cold/heat differentials are extreme enough (as well as other conditions allowing). Aerodynamic dashed linear contrails closer to aircraft and what the Chinook is producing.
Day 2 of Extreme Cold Warnings (-29 / -27 respectively overnight). Fly-bys within 20 minutes of each other around the noon hour. My instruments read 10 above zero w/minus 2 showing as Helena temp, lower in altitude and cold sink. Likely damn cold up above!
Aircraft operating out of Fort William Henry Harrison (or the airport w/training lifts out of the base; still haven't figured that out. Major training area but when I worked there I saw a majority of tanks/heavy armor). Believe these are Montana National Guard and/or Army.