Warm front + cold front = storm front. This equation was spectacularly obvious last night as we watched a massive storm front bear down on our town. We are somewhat used to emergency alerts in our part of the country - blizzards, floods, damaging winds, and tornadoes. First the national weather service alert shows up on TV, then we check the radar map online, sometimes the sirens go off, and then most of the time the worst part of the weather goes to the north or south of us. Not this time.
The closest we saw to a funnel cloud forming.