Stator
Having just completed almost 5 months in Riyadh over the winter, I too had an eyeopener with respect to the weather in the desert areas, not all sun and sand by any means. I experienced exactly as you did, completely unforecast, or at the very least grossly underestimated winds and vis. with PROB and TEMPo's way above the actual weather. In March we had three days of CB's, high winds and low vis due to blowing sand which typically lasted two hours staring around 1600L. There was a depression moving across Arabia from Africa which seemed to be cooler/moist air pushing up against the warmer drier air. The result was a dry gust front with winds and blowing dry sand which reduced vis to 200m or so, followed by rain and sustained winds of over 50 kts lasting an hour and one or two occasions. The single most important lesson I learned was a respect for desert weather and not to trust the TAF's I read. Alternate selection is one to consider carefully.
I just did a quick Wik search and came up with the following link which might be of interest.
http://www.answers.com/topic/haboob#after_ad2.