Originally Posted by Captain_Bigelow
You really want to get the lagering temperatures down to the low 40's. I picked up a small chest freezer off craigslist for about $50 and then added a Johnson Controls thermostat. It works great.
If you're talking about fermenting a lager, low 40's is too low. 50-55 is ideal, as you can see on White Labs
But I was in a rush earlier and really only did give half an answer. I should have pointed out that making a lager is really split into 2 parts:
1. Fermentation (1-2 weeks at 50-55F)
2. Lagering (a few months at around 32F)
So to answer your original question, yes, you could ferment your lager at 50F no problem. And if you had a well made swamp cooler you could probably even lager it for a couple months, but it would be a pain. A chest freezer would be ideal.
The swamp cooler is really better for fermenting ales at cooler temperatures.