Sunday, September 24

Severe weather risk Tuesday night in KC

KANSAS CITY, Mo.—Good morning bloggers,

A severe weather risk has been placed over our region for Tuesday night. The Storm Prediction Center has placed a hatched area showing where strong tornadoes are most likely and I will share this with you here in just a second. Let’s discuss this approaching storm as there are several possible scenarios to how this potentially dangerous weather event will play out.

Let’s begin by looking at our prediction for this week made over 100 days ago:

Severe Weather Prediction

I plotted the top two maps on Jan. 5 after we narrowed in on this year’s LRC cycle length. The LRC describes the cycling pattern of the Northern Hemisphere and this year’s cycle has been close to nine weeks long. This part of the pattern cycling through this week is the part of the pattern that produced two major severe weather outbreaks in December, and also in the first cycle of this year’s LRC in October. Mayfield, Kentucky, was devastated by a long track EF-4 tornado that killed 56 people. 90 people were killed that day on Dec. 10, 2021. Then, five days later, on Dec. 15, there was another major severe weather outbreak that produced 77-mile per hour winds in Kansas City and tornadoes over northern Iowa, Wisconsin and Minnesota. These areas had never reported a tornado that late in the year since records began. Both of these parts of the pattern will cycle through in the next two weeks. The first one is Tuesday/Wednesday and the second one will begin showing up next week. That second one is the one I talked about and predicted on our spring weather special two weeks ago.

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The Storm Prediction Center outlook for Thursday night:

Severe Weather Outlook Monday

Severe Weather Outlook Monday

Tornado Hazard

Tornado Risk Tuesday

These two graphics above show the SPC severe weather risk for Tuesday into Tuesday night and the tornado risk. The hatched area is quite concerning as they only put hatched areas when strong to violent tornadoes are expected. That means there is a 10% chance of a strong tornado within 25 miles of any point. This still means that there is a 90% chance there is no strong/violent tornado in your area as well.

From The SPC: The primary uncertainty remains how many thunderstorms will initiate along the length of the dryline late Tuesday afternoon into the early evening, as mid-level height falls/ascent preceding the upper trough will remain fairly modest. Lingering convective inhibition may also hinder coverage to some extent. Even with these uncertainties, it appears likely that isolated to scattered thunderstorms will form along the dryline from parts of central TX northward into central/eastern KS. Any thunderstorms that can develop in this very favorable thermodynamic environment will likely become severe quickly. Given the large reservoir of buoyancy available, supercells will pose a threat for very large hail (2+ inches), along with damaging winds as they develop eastward through the evening. A southerly low-level jet will rapidly strengthen Tuesday evening across this region, and a corresponding increase in low-level shear is anticipated. Any supercells that persist will be capable of producing tornadoes. With the strength of the low-level shear that is forecast, a strong tornado appears possible.

There are a few different possible scenarios:

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We are strongly leaning towards Scenario #1 at the moment. Let’s look at the setup:

Surface Forecast Valid 4 PM Wednesday

Surface Forecast Valid 4 PM Wednesday

A surface low-pressure area will be intensifying over Nebraska and South Dakota Tuesday afternoon. By 4 pm the center of this strong system will be in central South Dakota. A cold front will trail out of this low and be tracking across northwestern Kansas tomorrow afternoon. There will be a nearly stationary dry line (the brown line with the semicircles that you can see if you look closely). It is forecast to be near Wichita. Notice the temperature in Wichita is forecast to be 86 degrees at this time. High humidity will be surging in from the Gulf of Mexico ahead of the dryline and this is the fuel for these thunderstorms that will begin forming.

Most of the models show the “cap” that is preventing thunderstorms from forming during the day. A “cap” is a layer of warm air between 5,000 and 10,000 feet up that is so warm that the air just below it is colder, and thus it isn’t able to push through and break the cap. To break the cap, we will need one of several possible scenarios:

  1. It will heat up so much below the cap to allow the hotter air to rise and break through. This is unlikely as it will need to get up over around 94 degrees to do this Tuesday. The cap is that strong. The forecast highs are in the 80s and it may not be enough
  2. Convergence near the boundaries will become strong enough to force the warm/moist air through the cap and explosive thunderstorms would result. This is only likely when the cold front catches up with the dryline after sunset.
  3. Colder air aloft moves in with the developing storm system. This will likely happen from 9 pm to midnight as you can see below.
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Thunderstorms Form Tuesday Evening

Thunderstorms Form Tuesday Evening

Once the thunderstorms form, the conditions are favorable for them to be severe with large hail, damaging winds and tornadoes possible Tuesday night. In most situations, nighttime thunderstorms are certainly possible, but as the hours go by and the atmosphere cools, we will have lesser of a chance of severe as sunrise approaches. In some situations, the risks will continue through the night, so we will pay close attention as these thunderstorms track our way.

By Wednesday evening, the risk shifts to Illinois south to Louisiana. This is the part of the pattern that produced the Mayfield, Kentucky, tornado disaster, so this area must monitor Wednesday closely once again.

Surface Forecast Monday

Surface Forecast Monday

So, there is a lot to go over on our weather forecasts today and tonight. We will provide updates as this storm develops later in the day Tuesday and especially Tuesday night.

Thank you for spending a few minutes of your day reading the weather blog and sharing this weather experience. We will go in-depth in our weather forecasts tonight on KSHB 41. Have a great day!


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