The 32-degree freezing line has set up along the southern edge of the Boston Mountains, thanks to colder air higher up in the atmosphere.
The map and chart below show the change in elevation between Northwest Arkansas and the River Valley. The difference of roughly a thousand feet is making a big difference. The freezing line will shift south throughout Tuesday Evening. Folks north will see freezing drizzle and sleet, while those south of the line will stay in a cold rain.
As of 5PM: The Freezing Line is near Mountainburg. Conditions on I-49 north of Mountainburg will be slick and icy into the overnight hours.
In the River Valley:
I-40 could get slick tonight as well, especially west of Sallisaw as colder air moves in from central Oklahoma.