Warm Wednesday may spark rare December thunderstorms

Following another quiet day Tuesday, the weather takes a dramatic turn as a potent storm brings a couple of different weather hazards into Minnesota, then much colder air behind it.

Tuesday’s forecast

Despite mostly clear skies overnight, which usually allows overnight temperatures to drop, Tuesday had a warm start for December thanks to breezy winds from the southeast. Morning lows are in the 20s and 30s, which is 10 to 20 degrees above average.

A few more clouds move in during the day, making for partly sunny skies, but those clouds do not hinder Minnesota having another mild day with highs ranging from the mid-30s north to the lower 40s south, putting afternoon temperatures well above freezing.

Another strong storm

Winds go from breezy Tuesday to gusty Wednesday as a strong storm approaches Minnesota.

Ahead of the warm front of that storm, a warm flow puts much of the state into the 40s, with some 50s possible in southern Minnesota.

Despite a the extensive snowpack in southern Minnesota, which limits the warming somewhat, many places could set records on Wednesday including the Twin Cities and Rochester, where the current records for Dec. 15 are 51 and 52 degrees respectively.

Because of the warmth, much of the precipitation that initially moves in with the storm will be drizzle or light rain Wednesday morning.

The rain becomes more persistent in the afternoon and evening hours, and the dramatic contrast of the warm air ahead of the system and much colder weather behind the storm with help provide the setup for a few thunderstorms in southern Minnesota.

Some of those storms may become severe, with the southern edge of the state under a slight risk area.

This is tremendously rare for December. The last time Minnesota had a slight risk issued in December was back in 2001. The primary risk is for damaging winds, but isolated tornadoes are possible.

Even outside of storms, winds will be very strong, with 30 to 40 mph or greater winds for most of the state by evening and through the overnight, and in southeastern Minnesota gusts may top 60 mph.

This has most of Minnesota under high wind watches (dark tan) and wind advisories (light tan) beginning Wednesday evening.

Meanwhile, the cold front side of the storm starts pushing into northwestern Minnesota by Wednesday afternoon, dropping temperatures quickly and making more of the precipitation snow.

Northern Minnesota could see up to 4 inches of snow Wednesday into early Thursday.

For places that see more of the precipitation as rain, such as the Twin Cities, rainfall of up to an inch is possible in some spots. Most of the precipitation ends by early Thursday.

The cold front side of the storm sends temperatures crashing on Thursday. Much of Minnesota will set highs at midnight, coming off the warm day Wednesday, then temperatures will fall into the single-digits north and 20s south by Thursday afternoon.

Winds diminish quickly on Thursday though, and skies clear with more sunshine by the afternoon.

The slightly cooler than average temperatures the storm ushers in are likely to linger through Saturday, with highs mostly in the teens north and 20s south.

Programming note

You can hear my live weather updates on Minnesota Public Radio at 7:49 a.m. Monday through Friday morning.