If I can maintain the same blistering pace I've demonstrated at The Alphabet Story Game at SparkleSystemSix, I should be able to crank out rough copy at about 500 words per 30 minutes -- presuming I don't go back to revise and "tweak," or to re-read and chortle over my own ingenious turns of phrase.
A potential problem, however, will be a lack of inspiration. At S3, I am able to "springboard" my entries off the ideas of other people. I take something that another person has come up with and "run with it." Left to my own devices, I quickly run out of steam. I don't find my own ideas as stimulating as I do those of others. Keeping a thread running, even nonsensically, for 50,000 words all on my own will be a challenge.
An additional challenge will be that of plot, of storyline, of beginning-middle-end. In my younger youth, in my grade-school and middle school days, I imagined one day becoming a professional ficiton author. This was before I had any real understanding of what was involved in writing a story. True, I was reasonably good at grammar, spelling, and punctuation. Mechanics, however, do not a writer make. Writers tell stories. I have no stories to tell.
I can embellish. I can imagine and record snippets of conversation. I can, with difficulty, describe setting, and with more difficulty describe action. I cannot, however, effectively work these details into the progress of a narrative, largely because I simply cannot come up with a progressive narrative. I write episodically; and even the episodes lack narrative structure. They're simply "bits" of dialog, "bits" of description. These "bits" don't lead anywhere. They just... sit there.
A look at The Alphabet Story Game will demonstrate this to be true. The progress in the story, a careful reader may notice, happens during L-O-C's and Sjon's and other authors' interludes. Then I come along and "fill in the blanks" with some extra dialogue or description or character interaction: padding, basically. I write the padding.
NaNoWriMo will be a challenge. I'll have a tough time stretching the padding out for 50,000 words.
On the positive side: if I don't stop to revise (which can easily double or triple the time), at 500 words per half-hour I should be able to complete the exercise in about 50 hours. An hour and a half a day should be adequate time to reach the word-count goal.
Even if I don't have a story to give form to the padding, I think it will be a worthwhile experience trying to come up with something reasonably coherent of short-novel length.
The last time I even attempted something like this was in early high school. A friend and I attempted, of all things, a romance novel, The Mansion of Love. Great title, eh? We quickly realized the limits of our abilities, and killed off all the characters in Chapter Two.