April 19: Significant Severe Threat Today

Paul Heggen's Weather Blog

1:30pm update: All of central North Carolina is now under a TORNADO WATCH into this evening.

We’ve already had two tornado warnings — no touchdowns, thankfully — and numerous severe thunderstorm warnings with the first round of rain. The next round will likely be significantly more intense, as temperatures are warming back into the 70s before those storms arrive. Everything I wrote in this morning’s post (below) still stands…stay weather-aware the rest of the day!

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POSTED 9:00 AM: A significant severe weather threat will develop in central North Carolina today — the Moderate Risk outlined by the Storm Prediction Center is close to the top of the scale (level 4 out of 5), and it represents the highest risk for our region since February of 2016:

I expect storms to move through in two waves — one around midday, another by early evening. The HRRR model’s radar simulation from 9am through 11pm shows that we won’t be storm-free in between those two main storm clusters, but we will likely see enough of a break for the atmosphere to re-charge:

The wild card in all of this is, how much do we warm up between the two rounds of stronger storms? The most-reliable data shows temperatures in the 70s by mid- to late-afternoon:That’s warm enough for enough instability (“storm fuel”) to build up and really feed the late-day storms. If we stay even a degree or two cooler, that will help…but if we’re even a degree or two warmer there will be even more energy in the atmosphere.

If the amount of storm fuel is still questionable, why is this such a big deal? The answer lies with the absolutely incredible amount of wind energy in the atmosphere overhead. If the storms can grow enough to tap into that wind energy, we’re off to the races. Damaging straight-line winds will be the primary threat — the Storm Prediction Center estimates almost a 50-50 chance of 60+MPH winds within 25 miles of any location in central North Carolina:That hatched area includes all of us, and indicates a 10% chance of 75+MPH winds. Those are hurricane force wind gusts, and would certainly be capable of the same damage as a tornado.

Speaking of tornadoes, that threat goes hand in hand with the damaging wind threat. The storms that develop ahead of the main line will have more of a chance to rotate and produce tornadoes, but little rotations within the main line of storms this evening could also prompt tornado warnings. The SPC shows also a 10% chance of that threat within 25 miles:Now, about those percentages…it’s natural to think, “Ten percent? No big deal.” While it’s true that it leaves you a 90% of being worry-free, keep in mind that almost every other day of the year our threat is ZERO percent.So it’s a significant risk, and something we’ll watch very carefully throughout the day.

Flash flooding will also be a concern, as we see more waves of rain falling onto the increasingly saturated ground. The Weather Prediction Center has included us in a “Slight Risk” (level 2 of 4) of excessive rainfall, which would lead to flash flooding:

Large hail isn’t impossible, but it just won’t be the primary concern:

So at this point, most of you are somewhere at this level…

Let me emphasize the importance of being prepared instead of scared. Here’s what you should do:

  • Have a reliable source of weather information with you throughout the day. Make sure your weather radio’s batteries are fresh, turn on your cell phone’s emergency notifications, and set up the CBS 17 weather app to notify you when warnings are issued.
  • Speaking of the app…that will allow you to stream our coverage if your power goes out. Pretty easy to watch us from your safe place! (Better than the transistor radio I had to use in the basement when I was growing up…)
  • Have a plan! If you’re at work, at home, out running errands…know where you’ll go if the weather gets nasty.
  • Stay updated on the latest information. I’ll be posting updates on social media throughout the day, and of course we’ll be on the air during our regularly scheduled newscasts.
  • On social media, Twitter is BY FAR the most useful platform when warnings are issued — just make sure you’re seeing “latest tweets” in your feed. Facebook is useless when it comes to information that changes on a minute-by-minute basis.
  • Finally, think about your pets! Have the thunder-shirt ready for storm-phobic dogs, and have a shelter available for outside animals.

We’ll be here all day keeping an eye on things…

Easter weekend will be calmer — just an isolated chance tomorrow and to start the day on Easter Sunday. Cooler and breezy conditions Saturday will give way to a slight warm-up Sunday, then a more noticeable warming trend early next week:

Meteorologist Paul Heggen: Twitter & Facebook Instagram

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