(Temporary) One-Way Action on Fifth Avenue in Sunset Park?

Is Fifth Avenue going one-way in Sunset Park? We haven't seen anything about this, but a reader sent us the photo above, which shows a new one-way sign waiting to be uncovered at Fifth Avenue and 34th Street that bears all the signs of some temporary changes. (That's Green-Wood Cemetery in the background.) He writes:

Today I noticed new "do not enter" (DNE) and "one-way" signs on 5th avenue at 34th street. In the picture, the "3" in "34 St" is obstructed from view by the one-way sign, but you can clearly see greenwood cemetery in the background. The one-way is pointing south-bound and the DNE facing north-bound traffic at 34th st suggesting that south of 34th 5th ave would continue to be two ways. The new pattern is not in effect as of yet--I presume they make changes like this in the dark at night.

I'm not sure how far north this extends or whether this is a temporary thing...I called 311 and was told that in order to verify a street sign or traffic change I would need to submit it in writing. I figured I'd ask you first since you seem to know the ins and outs of our fair and gentle borough so well.

Given the furor last year about one-way changes around Park Slope, we doubt that it's a permanent change. In fact, Fifth Avenue was left off the one-way list. So, we assume it's a construction-related issue. Anyone know what's up?