A question for weather watchers

<p>Yesterday we had some severe thunder storms sweep through the area, one at about 3 and another after 6.  I had left the house at 6 to get some errands done and while there were clouds they weren't that ominous looking.  When I returned about 20 minutes later the sky was definitely threatening.  I got on the weather radar internet page and saw that there was some wicked rain to the west of us moving northwards, and that the whole system was moving fast but consistently west of the city.  Went out and the sky had turned green.  Went back down to the weather channel, not 5 minutes after the first attempt and the situation had changed dramatically, we had an "event" form right over the city. </p>
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<p>We got some heavy pea sized hail and rain, some lightning but nothing significant beyond that, farther east on the flatlands they had some tornado warnings...</p>
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<p>I guess my question is... can things change THAT fast?  From nothing to worry about to storm in 5 minutes?  Wow, you guys must have an eye on the sky all the time!</p>
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