How do specialty branch (AMEDD, JAG, CH, etc.) officer promotions work in the National Guard?

Promotions can work two ways. If you sit in a position of higher rank, say 1LT in a CPT slot, the state can choose to vacancy promote you in that slot. This type of promotion is very rare and usually the position is a critical position. The most common is the federal board process. This is based on time in grade. You are notified that you are in the zone for the board and you get your ORB and iperms up to date. The bird convenes in DC. It takes 3-4 months for the board results to be published. If you make the list, your unit is to recommend you for promotion, it goes up through the TAG and then to the Governor. This takes about 3-4 months. Your date of rank is when the Governor approves, not the board publishing date (which is the case for the Reserves since it is federal). You also have to be sitting in a position for that rank. Medical is a little different, you can promote 1 grade above your paragraph line number.

A friend of mine was in the NCArNG. Started as a CPT, MC and every 3 or 4 years he was promoted and in 12 years was a COL, MC. Never promoted again and retired as Colonel.