Summer For A Day, And Severe Weather Chances

***Watch WISN 12 News for the latest on the possibility of severe weather!***

Thank you for stopping by the Weather Watch 12 blog.  Big swings in temperatures and two chances for severe weather are in the forecast from the early morning hours of Sunday through Sunday night.

Any remaining ugly piles of snow from this winter, like the one below that resides at the end of my neighbors driveway, will quickly vanish over the next two days.  The first snow of the year is always beautiful, but by April it becomes an eye sore.

Dirty Snow April

A quick shot of summer is in the forecast for Sunday.  Highs should touch 80 for the first time since October 10 in Milwaukee!  Below is the summer-like temperature forecast from the 12Z NAM computer model.  This map is valid at 1pm Sunday.  This has upper 70s to low 80s over a good part of the area.

NAM Temperatures Sunday

That is the warm part of the forecast, now onto the stormy part.  Two rounds of storms are possible on Sunday.  The first round will arrive when most are sleeping very early Sunday.  Those storms developed in eastern Nebraska and western Iowa Saturday evening.  They were supercell thunderstorms and turned severe quickly.  Often we look at cool radar images, but how about looking at the storms from space – on the visible satellite!

Below is a visible satellite image around 6:40pm Saturday.  Look at the ‘bumpy’ clouds in western Iowa.  The tops of the thunderstorms were over 55,000 feet high!

Visible Satellite April 9

Those storms will cluster into a group called an ‘MCS’ or Mesoscale Convective System, overnight and move east along the warm front as it progresses north.  The storms will spill into southeast Wisconsin well after midnight.  If you hear storms overnight, make sure to first turn on WISN 12 to see if any warnings are in place or if we are on the air with an update.  Next check out interactive radar to track the storms here

Here is the severe weather timeline for the next 24 hours or so.  The timing of round one should come in after midnight and exit by 5-6am.  If you are in the path of the MCS heavy rain is possible with 1″ or more in spots.

Severe Timeline Sunday

For Sunday, the timing of another possible round of storms looks to be late in the day.  Pinning down this timing and location of possible storms may be tough.  The issue will be little boundaries called outflow boundaries that may be floating around our area from the round of storms overnight.  These little boundaries can act as invisible triggers that can help to develop thunderstorms when ingredients are right.

This is something we’ll watch closely on Sunday.  I like to compare baking a cake to a severe thunderstorm.  There are lots of ingredients that need to be mixed together in order for it to turn out right.  If one ingredient is missing, then the cake, or storm will fizzle.

The Storm Prediction Center has outlined our entire viewing area and placed in the moderate risk area for severe weather on Sunday.

Severe Weather Outlook April 10

This outlook will be updated several times on Sunday, so look for updates here in the blog.  I think if storms can initiate in southern Wisconsin late Sunday afternoon or into the evening isolated tornadoes may occur with discrete supercells.  There will be lots of shear, or winds moving at different directions in the atmosphere on Sunday which will help the storms to rotate.  But the big question is will storms initiate?  Our in house model the RPM keeps the severe storms closer to low pressure, and also south of our area Sunday evening.  See below.

RPM Storms Sunday

If the thunderstorms hold off and form closer to the cold front, then some of the best dynamics may be north or south of our area with the threat shifting to more wind/hail.  So while the threat for storms exists on Sunday, there are still some question marks.  The above map would line up with cycle 2 of the LRC.  Could the precipitation pattern mirror this part of the cycle too?

Precipitation December 31, 2010

In just over 24 hours all the answers will be supplied by mother nature!

Make sure to stay with WISN 12 for the latest weather information!

Jeremy Nelson


11 Responses

  1. Might just be my interpretation, but it looks like the first round of storms are moving northeast on a path that would take them into central Wisconsin, perhaps missing us in the process.

    • I saw the same thing. Unless there is additional development the two radars I have seen have everything moving northeast.

      • Craig,

        The storms are moving northeast, but the warm front bends southeast. The storms will want to stay close to the front and moisture source overnight. That is why the storms should move east and maybe southeast a bit over time. The best chance for storms is Milwaukee and points north tonight. Could be some south, but chances are higher north.


  2. Wow– I’ll be traveling throughout Chicago and arriving in Milwaukee around 4 PM. Just in time for some fun. 😉

  3. Hang on tight. Great environment. Its gonna get a bit dicey…

  4. So, is Bristol, Kenosha area supposed to get the worst? First I read SE Wisconsin was going to get the worst.. Now, they’re saying it’s going north?

    • Yeah, that would be a shame! That’s the way it’s looking right now :/

    • Brandi,

      Not sure who ‘they’ is but there is still a chance of severe storms. Increased threat farther west and northwest of our area. Still need to watch this closely later today. As I said in the blog there seems to be a question of whether the storms will fire in our area, or stay closer to the low.


  5. The shifted the moderate risk area to the north and west…but I’d still look out for some dangerous storm. They still have all of SE Wisconsin in the 10% risk for significant hail, and they put us in the 10% risk for tornadoes. Hopefully, they’ll change their minds. 😛

    • Hopefully all the severe storms miss our area.


  6. When do we warm up in Sheboygan? Lake breeze?

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