It should eventually cover the whole state, as the southern edge reaches well into Oklahoma, possibly south of I-40. I'm in Wichita now, it is not yet as bad as initially forecast (2-4 inches of ice?) and traffic is keeping major city streets clear at day time temperatures, but the rain is still there, temperatures will drop again, storm warning for here extends well into Saturday.
Timing will be different for different places, might not yet have reached the Oklahoma/Missouri/Kansas corner area, nor much of Arkansas before Sunday. Storm is slow moving, almost stalled, which is why forecast for S Oklahoma, N Texas, S Arkansas suggests up to 4-6 inches of rain before Monday.
If thinking about traveling, inquire locally, be prepared to stop if you catch up with it going east, or wait for it to pass if you run into going west.
Normal Thankgiving through New Years weather for Kansas, Missouri, Southern Illinois, pretty much anywhere east of Rockies between I-70 and I-40. North of that, snow, south of that heavy rain.