Thanks to a stalled peak trench pattern, the Upper Midwest has experienced several days of record heat and threats of extreme weather.

However, today will be the last day as the flow is finally starting to move again.

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The lows hovering just off the southeast coast have begun to recede to the west. This will allow the ridge to escape to the east. Certain low levels will then be reabsorbed into the jet stream and discharged early next week. We then enter a period of more geotropical runoff that is often not very supportive of severe widespread threats.

So today is the last significant threat, at least in the medium term.

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A negative skewed shortwave is passing through Intermountain West. Ahead of it, under a warm front moving north, was an atmosphere that was already conditioned and awaiting activation.

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The dew point in this area is already above the 60s on/lows of the 70s and is expected to rise even higher as more moisture builds up north.

If you’re thinking the 70s dew point looks high for the upper midwest in May, you’re right. They usually run 20 to 30 degrees higher than this time of year. That is what helps facilitate a significant threat to the region today.

Let’s look at the conditions as of this morning.

This is an observed sound from Chanhassen, MN, located just east of the defined Medium risk region of the SPC.

  • A sturdy hat is in place, however, with daytime heating and moisture absorption, this hat will wear out with daily wear.
  • We have dry air overhead to ward off the threat of damaging winds.
  • Strong shear (on rear run) is already stable and will only improve as the low-end jet gets stronger. Winds are expected to reverse from the southeast along the warm front, making it the focus for the possibility of tornadoes.
  • Colder overhead air means that the rising air is much warmer than the environment, allowing strong winds to blow. Strong winds are required for large hail and storm intensity in general.

Today, all hazards are possible, however, some have limitations.

Any cyclone activity will likely be limited to near the triple point and/or warm front where shear is maximum. Here, surface winds will return from the southeast, reinforcing low-level shear. However, the window for discrete cells is expected to be short-lived, so this threat may not be long-lived. Of course, tornadoes over the QLCS are still possible as it heads east into the evening/early hours of the night.

With strong winds going on and much colder air overhead, heavy hail is a threat, especially in any loose cell that may form/exist.

Harmful winds will be today’s main threat. High-end growth into a line is expected to be quite rapid.

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A medium jet with winds in the 80 kt range is forecast over the area tonight. Now, this is 500 mb, so it’s less likely that 80 kt winds translate directly to the surface. But winds of about 65 kts (74 mph) were mentioned in the SPC discussion. Those are hurricanes, if you don’t know.

So while tornadoes and heavy hail are certainly possible today, wind is our main threat. I strongly recommend taking shelter for severe thunderstorm warnings just as you do for tornado warnings. I’ve said it before but straight winds can do as much damage as a tornado downstairs. Better safe than sorry.

As mentioned, this is the ultimate serious threat to the region, at least in the medium term. As the front passes, more weather temperatures await along with quieter weather.

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