What causes this?

Ok, the other night it was easier to see then tonight but like the warm seems to go around the mountainous areas or something? idk I never seen this happen till the other night. If it was just higher elevation it wouldnt be that big of an area with that much of a temp difference at night. Really I cant seem to think of why this is so maybe someone else can throw some ideas. Its nothing big im sure its just strange to me..

If you are talking about the cooler temps in Tri, its just sky cover and wind direction as well as being closer to the retreating cold still. They weren't under sw winds yet. They are up to 40 now.

I agree with John...lack of cloud cover+different airmasses...and elevation only adds to the dramatic affect of the cooler regime.

Is it not cold air damming in the valley? Looks like the temps follow the tennessee river, sw winds are prevented by the plateau from warming the valleys, and with low dewpoints, the temps can fall much further.

Jmundie, that actually might be it lol cause other night the lower temps looked just like that but went further southwest into like mid alabama and the temps was way colder then what that map showed it was like upper 30s and mid 50s everywhere around that area. I know it was warm yesterday enough to wear shorts but the ground was colder then ice barefooted my foot almost froze lol. Didnt know if that was something to do with it or not having cold ground and warmer air moving in.

Thanks Mundie thats what it is lol mountains blocked the warm air coming from the south and with a system further north at the right place pumped cold air in between them that got bottled up right as the warmer air surrounds the mountain area.