Created: 03/31/2009 11:07 AM KSTP.com | Print Story By: Dave Dahl

Now that the first tornadoes of the year have made it as far north as South Dakota, it's time to start thinking about our severe weather season as well.

A powerful spring storm that dumped over 2 feet of snow on the Black Hills of South Dakota also produced that state's first tornado of the season on March 23rd.  An EF-1 produced some minor damage to farm buildings 5 miles southwest of Springfield South Dakota in the far southern part of the state.  There were over half a dozen other tornadoes reported across Nebraska that day.  

When spring storms develop early in the season as they have this year, it usually foretells of an active severe weather season.  The jet stream happens to be very active right now, which means a few more storms are possible over the next couple of weeks.  With snow still covering the ground in far northern Minnesota, and virtually bare ground in the southern part of the state, large temperature contrasts begins to build.  High temperatures this time of the year can easily top 70 degrees where the ground is bare, while areas with snow cover can stay in the 40s.  Since the atmosphere doesn't like that much of a contrast, something has to break.  Low pressure areas act like mixers in the atmosphere, blending the warm and the cold together.  The larger the temperature contrast, the stronger the storm system.  

Our peak of severe weather here in Minnesota and western Wisconsin usually occurs in June and July.  This year we might get our peak a little earlier, starting in May but still lasting through July.  Last year we had a total of 43 tornadoes across the state, which was a dramatic increase from the 18 we had the year before.  This year we could end up topping last year's total just because of the earlier start to our active pattern.  Tornadoes are most likely just after the peak heating of the day, which means they'll occur most often from 3 PM to about 7 PM.  Severe thunderstorms with large hail and damaging wind are also most likely during those times, but can occur frequently during the overnight hours as well. 

Have a great day!

Meteorologist Dave Dahl