I had a similar problem while travelling and I rang UBS. They were very helpful and I was able to send a fax with my signature providing I also followed up with a letter within a given time.

Alternatively do you have online banking? UBS does have that option, you can then just log in and do it all online, even if you did so at midnight and then they'll carry out the transfer the next day.

HOWEVER, I've had transfers to the US take me about 5 business days in the past... No experience with Western Union so can't help you there but might be quicker...