JNU CIC/Ground Controller reported a local controller failed to properly identify and separate two Cessna Caravans on final which resulted in the VFR Caravan taking evasive action to avoid the IFR Caravan.

Narrative

Aircraft X was on the V approach into JNU from the west. The weather was awful on final. (Moderate SN.) A second caravan (Aircraft Y) called in bound about 10 miles out to the west. The pilot was told he'd be number 2. The Local Controller had assumed that Aircraft X was having ADSB issues earlier on and told them they could reset/turn it off. We could not see the target any more after that. I was on Ground Control/CIC (Controller in Charge) and getting nervous about the position of the first Caravan in comparison to the 2nd. I had the Local Controller ask position and altitude since he hadn't done it himself. The second Caravan replied and said they were in the same vicinity as the first (4 mi final). We could not see either aircraft out the window; just the 2nd Caravan tagged up on the screen. The VFR pilot then pulled himself off final and headed for the snow showers to the south. After the Controller finally asked; the altitudes were reported at 006 ft. and 008 ft. on a 4 mile final. Neither one had been told about each other being that close until I had the Controller reach out and do their job. I believe if I had not been watching them; something bad could have resulted from this. The second (VFR) Caravan circled for a few minutes toward the bad weather; while the first one on the IFR approach landed several minutes later. Give appropriate traffic calls on local 1 and do your job. Those 2 aircraft were the only ones on frequency and the service that was provided was not acceptable. We should be even more vigilant in harsh weather; not completely lazy.