Funnel clouds danced over parts of Iowa yesterday, but no warnings or sirens went off. National Weather Service forecaster Miles Schumacher says the changing weather caused what are called “cold-air funnels.” A cold front coming in over top of a warm one will make it unstable, but there’s no severe storm going on. Schumacher works at the Johnston office of the Weather Service, and says cold-air funnels aren’t linked to the kind of big storm that causes damage.There may be small showers and the cloud forms and might even spin, but rarely will the funnel come down to the ground. Some folks will say a dark-colored twister’s more dangerous than a light-looking one but the meteorologist says color’s not a good guideline. Schumacher says if you spot a funnel it’s always a good idea to call a local weather-service office or law enforcement, so they can check out the twister and have experts identify whether it’s the dangerous kind.