Blue line with blue arrows

Some days at certain times of the days depending on the hour, I get either a blue line with blue arrows and other times with a red line with blue arrows. The line always runs from the NE to SW. Please assist me with the answer. Thanks from a Newbie

Phil
It will be frontal systems. You can turn off their display in the settings.

See: https://en.wikipedia.org/wiki/Weather_front

Ventusky
Thanks so much and that is what I thought. I will be leaving it on as it adds more info for me