Subject: Is the average air pressure in Death Valley lower than at sea level?

I have been trying to find information to answer a student's question. 
I teach middle grades gifted science in Peachtree City, Georgia.  The 
question posed was since we learn that air pressure decreases with 
altitude, being theoretically less on a mountain top than it is at sea 
level, would it be even less in Death Valley since it is below sea 
level.  My instinct tells me that other factors involved such as 
temperature and weather conditions would be more at play in the 
measureable air pressure difference than just altitude--but I need 
evidence to support my hypothesis. I have used Infoseek, Excite, and 
Yahoo and found thousands of sites, but none that I can find a 
concrete answer to this question for my sixth graders.  Any light you 
could shed on this subject would be greatly appreciated.

Re: Is the average air pressure in Death Valley lower than at sea level?