Severe weather potential for southern Minnesota; historic April blizzard in North Dakota

To use a technical weather term, this one looks like a doozy folks.

A powerful April storm brings rain, thunder severe weather, and heavy snow into the north-central U.S. Tuesday. Minnesota will span the range from snow in the northwestern part of the state, to possible severe storms and even tornadoes in the south. It’s a reminder that Minnesota is a tall weather state.

Historic North Dakota blizzard

Let’s start on the cold side of this storm. Heavy snow and blizzard conditions are almost certain across much of North Dakota for the next couple of days. This system looks likely to drop 2 to 3 feet of snow across western North Dakota. Blizzard warnings are up for the western half of North Dakota.

Snowfall will include areas of northwest Minnesota. Snowfall totals could be heavy in the northwest corner of Minnesota.

Severe weather risk south

I wrote in detail about Tuesday’s severe weather risk for the Twin Cities and southern Minnesota earlier. The most favorable zone for severe storms including possible tornadoes still favors southern Minnesota.

NOAA’s HRRR (18Z) model run develops storm clusters in southwest Minnesota by around 6 p.m. Tuesday, then a longer line of storms extending into the Twin Cities later Tuesday evening. The loop below runs between 6 p.m. Tuesday and midnight Wednesday.

Severe weather forecast parameters indicate all modes of severe weather look possible Tuesday evening across southern Minnesota. Damaging wind, large hail, and even tornadoes are possible.

To my eye, the highest tornado risk zone looks similar to our December 15 outbreak. I can’t rule out a stray tornado near the Twin Cities, but the highest risk area favors the I-90 corridor once again northward through about Red Wing. Austin, Albert Lea, Rochester, Owatonna, Northfield and Winona are all in an area that has enough wind shear for possible tornadoes between about 7 and 10 p.m. Tuesday evening. Iowa has some really eye-opening significant tornado risk parameters Tuesday evening.

The Twin Cities NWS Office has a nice little forecast discussion on our Tuesday evening severe threat. Check this out and feed your inner weather geek.

TUESDAY EVENING SEVERE WEATHER

Our main concern until Thursday will lie with the severe weather threat Tuesday evening. Guidance has trended slower with the onset of precipitation, as the surface low and better forcing aloft do not appear to arrive until late Tuesday afternoon at the earliest, and more likely Tuesday night. MUCAPE values of 500-1500 J/kg will be present along and south of Interstate 94, with the highest values along the I-90 corridor. Wherever this instability is realized, deep shear values in excess of 50 kts will create an environment prime for organized updrafts and severe weather. The timing for this severe threat looks most likely between 6 PM to midnight, when the surface low is forecast to pass through the region. The main question remains whether any of this instability will become surface- based, which will play a deciding role on the storm mode and possible modes of severe weather. The most likely scenario at this moment is that the surface low and warm front remain south of the border across Iowa, which would mean thunderstorms will remain elevated and mainly carry a threat for large hail (possibly golf ball sized or larger). A damaging wind threat could also manifest if storms form into linear clusters, which looks possible later in the evening, allowing strong wind gusts to overcome the capping inversion. Rotating supercell thunderstorms are possible initially early in the evening across southwest and south-central Minnesota (along with the greatest threat for large hail), with thunderstorms expected to become more linear later in the evening as they move through Wisconsin.

Much of southern Minnesota could pick up another .50” to 1”+ rainfall Tuesday night.

Expect severe weather watches Tuesday evening, and possible warnings.