“A very large and historic dust storm moved through a large swatch of Arizona during the late afternoon and evening hours of July 5, 2011. Widespread reports of near zero visibility and winds gusting over 50 mph were received by the NWS Phoenix office.” National Weather Service Report at 11:00 PM July 5th
AZCentral.com has a good page on it here.
Read more about desert storms here, “Spectacular walls of dust, called “haboobs,” dominate the sky, overtaking entire sections of the city. I have learned that a haboob holds the promise of photogenic storms soon to come. Something out there is alive and kicking. ”