Dreary Start to The Weekend And Heat Burst Explained

Not the nicest weather today to start the weekend with showers, fog, clouds, and cool temps. What an incredible difference in just a few days. The high on Tuesday was a record-breaking 97 degrees. That is 23 degrees above average. The high Friday was 54 degrees. That is 21 degrees below average. Just another late spring day/early summer week in Wisconsin. Our high temperature range is even more dramatic than other areas around us thanks to the cool waters of Lake Michigan.

Thankfully, the weekend weather will be much nicer than it was today. After we get through some fog and showers Saturday morning, skies should begin to partially clear on Saturday afternoon. Sunday will be the pick day of the weekend.

Temperatures will be warmer inland on both days. If you are in Waukesha westward on Saturday, you should hit 65. On Sunday, 70 inland is likely. Enjoy.

Now, on to a topic I was going to discuss on Wednesday, but severe weather got in the way. We experienced something in our area that I have never seen in my 14 years here. It is known as a heat burst. A heat burst occurs when a thunderstorm or area of showers dissipates. Normally, this brings rain cooled air down to the surface. However, on Wednesday morning in parts of Southeast Wisconsin the base of the rain showers was quite elevated. We can thank our warm temperatures for this. As the showers dissipated, the descending air that was saturated started to evaporate. As the air continued its downward motion without any more rain it compressed and heated as it reached the surface. The results were pretty dramatic. Take a look at three locations and the huge change to temperature and the dew points. Thanks to the NWS in Sullivan for sharing the observations.

                                              BEFORE        AFTER         MAX WIND GUSTS
MILTON                               76/65/69        92/46/21      42 MPH
WHITEWATER                   78/66/67        89/49/26      55 MPH
FT. ATKINSON                   76/64/67        88/43/21      35 MPH
SULLIVAN WEATHERX    75/67/76        82/59/46      32 MPH

The biggest gust was created in Whitewater at 55mph. The largest temperature rise occurred in Milton was a 16 degree change. This occurred in a matter of minutes.

What is interesting is that another heat burst occurred in Wichita on Thursday night. This part of the country is normally where you would see “heat bursts”. The temperature spiked to 102 degrees at 12:24 AM. 20 minutes earlier the temperature was 85 degrees. They also had 70 mile per hour winds.

The key to getting a heat burst is a high altitude shower or thunderstorm falling apart and then rushing to the ground in a rain-free area. Otherwise, when the air rushes out of a thunderstorm it is usually much cooler than the surrounding surface. Fun stuff for a meteorologist, but nearly impossible to forecast.

Have a great and dry weekend.

Mark

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5 Responses

  1. Is there a temperature range these usually occur in? What if the temperature was already above 90 degrees… could it go up to 110? Would be an interesting way to set a new all time record high here.

    • Daniel,

      The documented storms that I have seen all occur in warm weather and temps have risen into the 100-105 degree range. It certainly is possible to get an all-time record that way.

      There is a story from Portugal in the 1940s that has not been confirmed that the temperature rose to 158 degrees.

      Another in Oklahoma in 1909 where the temperature hit 136 degrees.

      Mark

  2. Mark,

    The big question that my friends and I have been asking since school let out has been “when will it feel like summer and warm up?”

  3. I’ll just be happy with a day where it is actually comfortable outside. Nine straight days now without a high temperature between 60 and 80 (here in New Berlin). At least it looks like the next two (could even be three if the storms hold off until Tuesday night) will be what I consider perfect weather.

  4. Hey Don!

    Looks like a pretty good stretch of ‘fishing weather’ headed your way. Hope you’re able to take advantage of it. Looking forward to you filing a complete report of your successes without any of that ‘you should’da seen the one that got away!’ nonsense. Enjoy!

    Cordially,
    Tony (Pl. Prairie)

    p.s. I’ll be trying to catch up on yard work so this place doesn’t look like it’s been deserted!

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