8-9 am will be fine - much of the traffic should be going southbound. Later in the afternoon, especially before a long weekend, traffic will get really heavy. For many, they plan on taking 3 days off next week in addition to Thanksgiving, so it should be a huge weekend for RV's leaving town.
After noon, you will see a lot of traffic, getting worse after 4 pm until around 8 or 9 pm.
Good luck!
You can check [www.maps.google.com]Maps.google.com and check up to the minute traffic in almost any large city!
Where are you coming from. Traffic getting to I-15 north can also be bad, depending on where you are starting at.
Fred.