http://www.occ.treas.gov/corpbook/group3/public/pdf/brclose.pdf See page 1 of the handbook re: change in hours - Advance notice is not required.
However, we critically look at transaction volume, staffing, and impact to the community (availability of alternate delivery services) before proposing a reduction of service. We do this across the board, no matter what the census tract income level. You may want to check with your state's banking regulator.
When we do reduce service, we post advance notice (30 day) at the branch.