Riddle Me This

Do you know why I'm doing a riddle tonight?  Because I can't think of a darn interesting thing to talk about!  So here it is:

MENACE

A menace, I creep

Silent and slow,

Obscuring your vision

And things that you know.

My blanket enfolds you,

But won't keep you warm.

You glimpse things familiar,

But I change their form.

By the sounds of the horn,

Know that danger is near;

By night or bright day,

It warns you to steer clear.

What am I?

as always, credit goes to Tower of the Riddle Master. 

psst!  I have a friend who blogs here... her name is Vodka mom. It's also the name of her blog.  Her blog is one of the funniest I've ever read! Anyway, she was nominated for the Top 50 Mommy Bloggers.  It would be really cool if you could check her out, read some of her stuff and go over to Babble and vote for her!  Last time I checked she was ranked #19!  Simply click here to go to the site.  Check out her blog!  You won't be sorry!!