"fishtailing" icon on 2007 prius

hi guys and gals, prius newb here. Bought my 2007 model with 108k miles on it about a month ago. Loving the car so far, but i've run into an issue i cant seem to solve.

occaisionally, while driving or when i hit the brakes a little too suddenly, i get the sensation that i am sliding on snow (even though it is late summer) and an icon pops up on the dashboard that has the image of a car "fishtailing" with curved tire skid marks behind it.

I talked to a local mechanic about this issue and he said the icon appears because my tires are not gripping the asphalt, causing the wheels to spin in place. There's plenty of air in the tires, and none of them look too bald as to cause such slippage.

Now, normally i would just ignore the issue, but the other day, the car in front of me suddenly stopped and i had to hit the brakes pretty hard. My car barely slowed down, the icon popped up, and for a moment i was fairly certain i was going to slam into the back of the car. Luckily my car stopped just in time. This incident has caused me to do further research into this issue, as i shudder to think what would happen if that same incident had happened on the highway.

Does anybody have any experience as to what i am talking about, or know how to prevent this from happening. Help would be greatly appreciated

 

checked brake pads today, seem to be just fine. Car begins to stop once minimal pressure is applied to brake pedal 99% of the time.