April 17: Severe Storm Possible Friday

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The next round of potentially severe thunderstorms will roll into central North Carolina about 48 hours from now, but at least we get to enjoy a couple of nice days between now and then. We’ll see plenty of sunshine and just a few fair-weather clouds today — that sunshine, combined with light southwesterly winds, will push highs into the upper 70s and low 80s this afternoon:

Temperatures tonight won’t drop too far, only to the 50s in most locations to start the day Thursday:

Despite increasing clouds on Thursday, we’ll still warm back up to around 80°:

I still have the same questions about Friday’s severe weather setup that I had 24 hours ago. We know there will be enough humidity to fuel severe storms, we know the wind energy in the atmosphere overhead will be exceptionally high, and we know that it’s going to rain. But the upper-level temperatures in the atmosphere won’t be all that cold, and if it rains early in the day temperatures near the ground may not be all that warm:If you were designing a severe thunderstorm outbreak, you’d set it up with very warm temperatures near the ground and cold temperatures aloft. The warm air near the ground helps the air rise to form storms, the cold air aloft ensures that the air keeps rising for explosive storm development.

We’re still a day away from getting a detailed radar simulation for Friday, but at least we’re getting some better hour-by-hour data today. The RPM model does show some rain to start the day Friday — the longer that rain lasts, the less we’ll be able to warm up:The strongest storms develop in two rounds on Friday — one by midday and early afternoon……another by late afternoon and early evening:The Storm Prediction Center’s forecast model shows a 70%+ chance that favorable severe weather ingredients will be present on Friday afternoon:Okay, but HOW favorable? We can measure that with a statistic called the Supercell Composite Parameter — anything over 3 is “high enough,” anything over 6 is a significant concern. Unfortunately, the same forecast model shows SCP values approaching 6 on Friday:At the same time on Friday, the Significant Tornado Parameter is over 1 — not exactly an “Oklahoma in May” value, but certainly enough to get our attention:With all of that in mind, it’s not surprising that the Storm Prediction Center has included most of central North Carolina in an “Enhanced Risk” (level 3 of 5) for severe weather on Friday:While that all sounds scary, keep in mind that this is still a potential severe weather event. There are plenty of factors that could help reduce our severe weather threat, but at this point you should definitely be planning to stay weather-aware throughout the day Friday.

The severe weather threat is gone in time for Easter weekend, although we may still have to contend with some lingering showers on Saturday. It’s lower than a 50-50 chance right now, so it won’t be an all-day washout — just be flexible with any outdoor plans, including Easter Egg hunts:Easter Sunday is looking quite nice! A cool start, then plenty of sunshine to warm us up to the low 70s. The warming trend will continue into early next week…


The nerd-links are back! For one day, anyway…I’m back on weather-and-traffic duty tomorrow and Friday.

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