I'm in an almost-identical situation to yours, with a slightly higher earned income, and was also looking at the same considerations, so maybe I can help. The link that Nothlit provided earlier is what applies to both of our situations.
In addition your salary, don't forget to consider any gains in any non-retirement accounts. Any dividends, earned interest (long-term savings, cashed-out EE bonds, etc.), and capital gains (if you sold or re-allocated assets) would also need to be added in, so keep that in mind.
The interesting question regarding the math here is whether the IRA contribution itself contributes to the MAGI, since we're in this weird boundary condition. My cursory internet research implies that it DOES count. Since ($83,000 - $18,000 - $3,300 - $5,500) == ($56,2000), assuming you don't have too much other income, you should be okay. Edit: Shoot, this is wrong. I incorrectly remembered my previous conclusion, and should have looked it up before posting. IRA contributions are deducted from your AGI, but then added back in to determine MAGI.
Since we're on the razor's-edge, you may also want to look specifically at when you receive your paychecks and project what you'll actually earn in 2016. For example, if you're payed once-per-week on Friday, you'd receive 53 paychecks this year, whereas in a different year it might be 52.
After doing the math, and assuming I didn't make any mistakes, I found that I'll end up just slightly above the $61,000 number where the phase-out begins. Like you, I had originally contributed to a Roth IRA earlier in the year, and about a month ago re-characterized my contributions to be traditional IRA contributions. If you want, you can wait and see what your MAGI ends up at when you prepare your 2016 taxes, and can re-categorize those contributions at that time. You can technically do it any time before October 15th, but It'll be easier to do the recharacterization before filing your taxes, or you'll have to file an addendum.
Assuming "the 585" refers to the Rochester New York area, hello from the 'other' Rochester (in Minnesota) :).