Check with your payroll department. Most payroll programs will assume that the lump sum will be paid each and every paycheck after that for the rest of the year. If yours does that too, they will withhold too much. You'll get it back the next year, but since the purpose of getting the lump sum in January is to invest it early...
So, find out, and then run the numbers.
Oh - never mind. You're putting it into a tax advantaged 403b, so they won't take out the taxes.
I'll leave my prior comment in case someone else gets a bonus and their 401/403/IRA slots are already filled.