April 23: Weekend Severe Storms, Links

The format of yesterday’s post seemed to work out pretty well, so I’ll stick with it for a little while…if you’re clicking here for the first time (or for the first time in a while), here’s the deal: I’ll be updating the blog daily — the posts will lead off with a discussion of our local weather, then I’ll share some nature- and science-related links that I find interesting.  Away we go!


Really nice weather today!  A bit on the cool side for this time of year, but a break from the rain chances is a nice change of pace.  We’ll be dry most of Friday as well, but clouds will thicken throughout the day, with showers moving in Friday evening.  The best chance of showers and storms will arrive after midnight Friday night — at this point, it’s still very up-in-the-air as to whether those showers and storms will still be around when the Country Music Marathon starts Saturday morning.  If you’re running or spectating, plan for rain and hope for a break!

Any storms we get Friday night and early Saturday could conceivably become severe, but the chances aren’t very high during that time frame.  The greater severe weather potential will take shape Saturday afternoon and evening, but it’s still highly conditional at this point…meaning there are a lot of “if this, then that” and “but maybe” statements at play.  The biggest of those: IF we see a substantial break from the clouds and rain chances in the late-morning and early-afternoon on Saturday, THEN our severe thunderstorm chances will increase substantially (and vice versa).

The Storm Prediction Center has already included the Midstate in a “Slight Risk” area for severe weather, along with a sizable chunk of the eastern half of the country:

Specifically, that means they’re estimating a 15% chance of severe weather (60mph winds, 1″+ hail, or a tornado) within 25 miles of any point in the risk area.  The situation is muddled enough at this point that they’re not outlining any “Enhanced Risk” or “Moderate Risk” areas (and the associated higher percentages) yet.  The uncertainty is not related to the wind profile in the atmosphere or the amount of energy available for storms to intensify — both of those factors look very storm-friendly.  The uncertain is related to how Friday night and Saturday morning’s rain chances will influence the weather set-up by Saturday afternoon…unfortunately, that’s a very difficult thing to predict more than 48 hours in advance.

If storms develop, the environment looks like it will be ready-to-go in terms of producing severe weather.  (There’s some serious weather nerdiness about to hit you, so if you want to skip past the maps I won’t take it personally.)  Some of the composite indices that we use to evaluate severe potential are very favorable around here…we’re in a region with higher values of the “Significant Severe” Parameter (anything over 20,000 is favorable for all types of severe weather, and our forecast value Saturday afternoon is 40,000…with even higher values in Mississippi):

We’re also forecast to be in a region higher values of the Supercell Composite Parameter (values over 3 will get our attention, and right now the forecast value is about 7.5):

Finally, we’re in a non-zero area of the “Significant Tornado” Parameter (anything over 1 is something we don’t want to see, and the southern half of the Midstate is at a 2 according to the latest data):

All of those indicate a situation that requires our attention.  However: THIS DOESN’T MEAN THAT SEVERE WEATHER IS DEFINITELY GOING TO HAPPEN.  Storms have to exist in the first place before they can become severe, and that’s the big wild card.

The computer-model radar simulations for Saturday are still all over the place, so I’m not even going to bother showing those here.  The thing to remember at this point is that any storms that fire up Saturday afternoon and evening will develop in an environment that will be conducive to severe weather…but it’s far from certain that those storms will even fire up to begin with.  As always, watch it, but don’t worry about it.  We’ll keep you posted.



All sorts of science-y and dorky goodness today…

About paulheggen33

Morning meteorologist for WNCN-TV in Raleigh.
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1 Response to April 23: Weekend Severe Storms, Links

  1. Pingback: April 24: Severe Weather Saturday, Links | 4WARN Weather Blog

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