It was Monday afternoon and the storm was shooting and rapidly turning severe, as forecast.

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While we’ve had a few tornado warnings so far north of central Texas, I still believe the “greater show” will be further south, perhaps between Austin and College Station . Storms are just making their way here so we’ll have to see how they progress. However, there is quite a bit of potential.

As tonight’s event is already underway, we turn our attention to what to expect tomorrow.

IF all the parameters combine in the correct way, tomorrow is likely to be quite a dangerous day for some. When the SPC uses words like “An outbreak of severe weather in the area, including the possibility of a strong tornado, is possible…” you want attention.

That said, forecasting is not a complete attack. Let’s see why.

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As we near dawn tomorrow morning, a turbulent storm stream will approach the Deep South.

While linear mode convection has its hazards (damaging winds, hail, QLCS tornadoes), it doesn’t have what it takes to create these powerful tornadoes mentioned in the SPC outlook. That type of tornado comes from discrete cells.

So for part of the threat to materialize, we’ll need discrete cells to form and survive in the warm open front.

Here’s the GFS that outputs the sound from weather.us. Again, it’s not as high-resolution as CAM, but still useful in identifying some important things.

  • Good cutting ability on the order of ~45 kts. Sufficient to maintain supercells without monitoring them. The surface rotates back from the SE, further increasing low-level torsion.
  • A slight limit exists at the lows. This limit will keep any waves from developing into a storm. If this happens, the warm region will be filled with fierce storms scrambling for fuel. With a cap in place, only stronger update lines will break through, increasing the chance of sporadic tiles appearing.
  • Cool, dry overhead air increases the rate of invalidation. A good lapse rate is essential for strength gains. A parcel cannot grow rapidly if its environment is not slightly colder than the parcel itself.
  • Low LCLs. As mentioned yesterday, low LCL is a common denominator in stronger tornadoes.

So some of the things mentioned above are necessary for the discrete cells ahead of the main line:

  1. At least we need a small cap to prevent messy convection.
  2. We need enough shear to maintain our supercells but not cut too much. Earlier in the year, we saw a promising project that couldn’t be delivered due to TOO MUCH cuts. Excess shear tends to blow the tops right out of the storm. Not a great thing if you are looking for those high and powerful updates.

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Models suggest a very powerful low-end jet which will obviously increase longitudinal shear quite a bit.

So while the higher end threat seems likely to be verified, it doesn’t quite fit. However, don’t bet on it failing. Prepare as if it will verify.

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Once again, the storms will approach unusual humidity. A PWAT value of 200 to 300% of normal is expected. Flash flooding can occur when sections of the line or storm in front of the line can manage to move parallel to the border (train). This is a risky day.

Over time, this will be primarily a late morning/afternoon event.

The line is forecast to weaken later in the day as it enters less favorable conditions. However, strong winds or QLCS tornadoes will still be possible in the stronger parts of the line.

Summary:

Severe weather is forecast for tomorrow morning/afternoon. If sporadic tiles can bloom in front of the main road, strong/dangerous tornadoes are possible. The line is forecast to weaken some as we approach the evening hours and conditions become less favorable.

As always, have a shelter plan with your safe space ready and can do it quickly. There are ways to get alerts and stay aware of the weather until the line passes through your area.

If there are any significant changes to the forecast, I’ll update tomorrow with a review of Wednesday’s setup.

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