Don't take this wrong, but I always find waiting on southwest kind of like a game of Russian Roulette. Do I or don't I? A few weeks ago I was putting myself through the same personal stress for my January flights. Flying out on January 19th flying back on January 27th.
Where are you flying out of? $160 seems high on Southwest for a one way flight, depending on the city (for example for Los Angeles that wouldn't be that high but for Kansas City it is VERY high) Also, Is it saying "web only!" in red next to it, or is it just the basic "wanna get away" fare?
Here is what I would do. I would watch the fare every day for the next week or two, if it doesn't go down, then I would go ahead and book it at the lowest fare available. Usually the basic fares don't change much (its just those web only that change all the time!) Chances are between now and two weeks from now at some point in time Southwest will offer some kind of web fare.
I would also HIGHLY recommend signing up for their e-mail alerts This is different from DING you get e-mails from Southwest once or twice a week announcing their different fare sales.
Also keep in mind if you do book a fare, and then the price goes down you can always rebook at the lower price and get a credit back from southwest to use on a later flight (within 1 year).
Jennifer