Poly pro and field jacket liner will usually do the trick.
Dollar for dollar, the field jacket liner is the second greatest piece of gear ever created (next to the poncho liner). It's even better than sliced bread.
Another thing to consider before you become a TBS gear queer and make the UA folks richer is that once you reach Pensacola, you will pretty much have no use whatsoever for cold weather UA gear (for a year or two, at the very least). Even last week, when the temp in Milton reached 30 degrees, the green/green sweatshirt/pant combo was more than enough to keep you warm until 0800, when the temps shot up towards 65. (Also, the dead cows are finally in at NASP gear issue, so you'll have something warm to wear over your bag.) Though I've never been to Corpus, Kingsville, or Meridian, I can't imagine they are much colder than Milton.
You'll spend a month's pay at TBS to Protect This House, and all the gear that seemed so important to buy to "fit in" at TBS (and trained you to be a sea lawyer, as you tried to figure out when UA was/wasn't authorized to be worn) will sit in a box dry-rotting for months/years once you come down to FlorAla. By the time you get winged, assuming you don't get orders to California, Hawaii, or Oki, UA will have even more newer and overpriced nylons for you to wear for the short time you are actually in North Carolina...before you go play in whatever sandbox we are frequenting at the time. (Also, by that time, MCO 1020.34G will have been amended 15 times, all in a devious plot to further disrupt your sea lawyer career.)
Instead, just spend your TBS money on your All Weather Coat (which you will never wear either, but you are required to own).