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Concern About Afternoon Lightning, Strong Thunderstorms

It’s much more humid at 9 am this morning (dew point 70) than it was at any time yesterday.

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This morning’s weather balloon showed 2,843 j/kg of Convective Available Potential Energy, or CAPE. Think of CAPE as the building blocks which make storms. You usually only need 1,000 – 1,500 j/kg for strong storms to happen. Models predict we will have 3,500 j/kg soon, and up to 5,000 to 5,500 j/kg this afternoon.  3,500 is PLENTY of building blocks to make a strong to severe thunderstorm.

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At it’s most basic level, a storm is a big and tall cloud. The NWS says today’s clouds should build “up” at an updraft speed of about 60 mph.

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The winds change direction the further up you go. This helps sustain storm growth and development.

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Lightning, strong winds, localized flooding, and hail potential.

This morning, storms were happening on the north side of a boundary draped across Davidson & Williamson Counties. Boundaries are often the focal point for storms:

This Afternoon

All the above ingredients will continue to build. Most models think storms will “explode” this afternoon, but there is debate about whether the storms will still be here by mid-afternoon:

WRF at noon delivers a healthy thunderstorm:

 

Lightning is a big concern. The WRF model thinks that noon storm will deliver frequent lightning:

By mid-afternoon, the storms will want to move east of us. We are on the edge of the activity, so we can’t say for sure what whether they’ll be gone by then.

HRRR at 3 pm – storming on us:

The RAP (shown below), gives us noon showers, then clears us out to develop storm activity east of I-65 around 3 pm:

The NAM agrees with the RAP. At 4 pm, the NAM sends the nasty weather east of us:

We will post updates to Twitter (@NashSevereWx) throughout the day.

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