July 22: Heat, Storms, Daily Links


Two big weather stories this morning: the excessive heat, and our storm chances later today.  We’ll tackle the heat first, since it’s the first thing that will affect you as you’re heading out the door.  The short version is, it’s gonna be hot.  REALLY hot:
PAUL iCast Temperature
And with dew points still hovering around 70, the humidity will push heat indices well above 100 degrees:
PAUL iCast Heat Index
Forecast heat indices of 105 are the trigger point for the National Weather Service to issue a Heat Advisory, which kicks in at 11am and lasts until 8pm:

However, I’m optimistic that we’ll get some relief from the heat (but not the humidity, unfortunately) with a decent chance of storms this afternoon.  As I’m posting this (around 8:30am), we’re watching storms off to our north and northwest:
Three different possibilities with these storms:
1) The storms fizzle out this morning, we don’t see any storms re-developing this afternoon, and temperatures end up even hotter than what’s forecast above.  I think this is the LEAST likely scenario.
2) The storms hold together and move into southern Kentucky by late morning, and dive south/southeastward across the Midstate through mid-afternoon.  As a result, temperatures only have time to reach the low to mid 90s.  Certainly possible, especially considering the storms are holding together so far!  It’s probably close to 50-50, but I think the most-likely scenario is…
3) The morning storms fizzle out, but the rain-cooled air pushed out by the collapsing storms (what meteorologists call an “outflow boundary”) helps trigger additional storm development by early to mid-afternoon.  Those storms then march south/southeastward across the Midstate — a similar path to that outlined in Scenario 2, but with slightly later timing.  This gives the atmosphere enough time to heat up to the level I showed farther up in this post.  The two most-reliable short-range forecast models both agree (more or less) with this scenario.  The RPM model’s version:
The HRRR model’s version is close to that — kind of a compromise between Scenario 2 and 3:
Keep in mind, models aren’t perfect.  It seems like every time we think we have a good handle on what Mother Nature is thinking, she kicks dirt in our face and steals our lunch money.  So, here’s the bullet-point version of what you need to remember:
– It’s going to be hot, and very humid.  Use your common sense to keep yourself safe.
– Storms are possible from midday through this afternoon, but not guaranteed.
– If it rains in your neighborhood, it won’t last all day.  Wait it out.
– A few of the storms could produce gusty damaging winds.

About that last point…the Storm Prediction Center has outlined a “Marginal Risk” (level 1 of 5) for severe thunderstorms in our neck of the woods today:
That means that while severe thunderstorm wind gusts are possible, they’re not terribly likely in any one particular location.

More heat, and more humidity over the weekend.  I’m sticking with a 30% rain chance both Saturday and Sunday, but stay plugged into the forecast for potential revisions — the daily rain chances in this type of pattern are largely determined by whatever develops overnight to our northwest, and we just have to take that day-by-day.  Today’s advice applies to Saturday and Sunday as well: prepare for the extreme heat, but be ready to adjust your plans for any thunderstorms in your area.
The worst of the heat wave should be over by the middle of next week, as we remain in a generally unsettled weather pattern.



This will be the last batch of nerdiness for the work week…ration these through the weekend so you don’t experience withdrawal symptoms.


About paulheggen33

Morning meteorologist for WNCN-TV in Raleigh.
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One Response to July 22: Heat, Storms, Daily Links

  1. Mary O'Neil says:

    These storms have downed a good few trees in green hills and around vandy i’ve noticed. here’s hoping Nashville can catch a break soon!

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