I wouldn't touch it. I am sure it is going to get much colder up there soon. When it gets down to single digit-F,
you can sprinkle some more fall leaves(I personally like oak leaves as mulck, since they will not rot or compost, when used as mulch over winter).
In the spring, when lows get to around 20F(or higher), you can remove some of that mulch so that ligh and air will get through.
But leaving most of it in place will have more benefits; Keep the roots cool, prvent weeds, maintain moisture.

I may be a little warmer than you, but I have taken to planting my garlic in mid-November to prevent top growth from poking through the mulch. 5-6" is not too deep so long as the leaves are finely chopped to prevent matting. If you get a spotty stand in the spring, dig down to see if the garlic tops are growing horizontally, i.e. unable to penetrate matted mulch. If so, just clear the mulch around the affected plants and they will recover.

TomNJ

Thanks for the replies. I figure if they do poke up through the leaves (which are semi chopped up and not matted yet) they will create a pathway through the matted leaves when the garlic resprouts in the spring.

i plant the 1st week of november. i use shredded leaves 6" thick. about 3/20 i check for growth and when they are starting to emerge i remove all the mulch leaving just 1". the key is to use finely shredded leaves.

i used whole oak leaves (big mistake) 1 year and i had 8" plants stuck under wet matted oak leaves! they survived but were unable to grow thru the weight and toughness of wet oak leaves.