Potent Outflows
Saturday, September 5, 2026 · 11:21 AM
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Lyrics
Major to extreme heat risk continues through this weekend with heat index values of one hundred five to one hundred ten degrees. A Heat Advisory remains in effect. Low chance of strong to severe storms this afternoon with damaging wind gusts as the primary threat. Heat risk lessens early next week, but temperatures remain above-normal through the forecast period. Step right up and look at the observation sites! Triple digit heat indices way before noon today, alright! Seven hundred Joules per kilogram of downdraft convective energy at seven A.M., On that morning Nashville sounding, heat ambient and wild again! Decaying mesoscale convective system slipping out over the Smokies east, But the afternoon heat is waking up a whole different beast! One hundred five to one hundred ten, the index is sky high! Damaging wind gusts dropping from the afternoon sky! Between one P.M. and six P.M., watch the atmosphere explode! Yeah, we're waiting on those potent outflows! Now the convection-allowing models can't agree on the play, Is it scattered in the heat, or a shortwave later today? Soundings creeping up to twelve hundred Joules per kilogram by five, If those downbursts hit early, honey, this party comes alive! Unstable airmass cooking down in Middle Tennessee, Ah, call out the wind, it's coming straight for you and me! One hundred five to one hundred ten, the index is sky high! Damaging wind gusts dropping from the afternoon sky! Between one P.M. and six P.M., watch the atmosphere explode! Yeah, we're waiting on those potent outflows! One hundred five to one hundred ten, the index is sky high! Damaging wind gusts dropping from the afternoon sky! Between one P.M. and six P.M., watch the atmosphere explode! Yeah, we're waiting on those potent outflows! Twelve hundred Joules coming down fast! Heat Advisory all weekend, baby! Get ready for the gust!
The forecast discussion
NEW SHORT TERM, LONG TERM
KEY MESSAGES
Updated at 1051 AM CDT Sat Sep 5 2026
- Major to extreme heat risk continues through this weekend with heat index values of 105 to 110 degrees.
A Heat Advisory remains in effect.
- Low chance of strong to severe storms this afternoon with damaging wind gusts as the primary threat.
- Heat risk lessens early next week, but temperatures remain above-normal through the forecast period.
SHORT TERM
(Rest of today through Sunday) Issued at 1051 AM CDT Sat Sep 5 2026
Things are already starting to heat up across Middle TN this morning.
Even before noon, several observation sites are reading triple digit heat indices and climbing.
As such, a Heat Advisory remains in effect areawide through 8PM tonight.
Will have a smaller segment take over through Sunday in the southwestern CWA due to lingering heat impacts but most areas will drop below criteria (105 HI) tomorrow.
This warm and strongly unstable airmass over the mid state region will contribute to our severe weather threat this afternoon.
A decaying MCS is noted off to the east over the Smokies as of 11AM, but most CAMs suggest another push of storms later today.
This morning's KOHX sounding revealed upwards of 700 J/kg of DCAPE at 7AM, which is plenty for strong downbursts already first thing in the morning.
With forecast soundings suggesting this to creep up to 1200 J/kg this afternoon and evening, watch for potent outflows (strong wind gusts) in any thunderstorms that develop over Middle TN in the heat of the afternoon.
Timing of this severe threat is very difficult to nail down just given the lack of consistency in the CAMs, especially since the first MCS is already pretty much out of the area and is not being resolved well.
If this convection adopts more of a summertime characteristic and is more scattered in the afternoon, the parameter space is much more supportive of severe storms between about 1PM and 6PM.
If nothing is able to develop until the second push with the shortwave later tonight (after 8PM), the environment will most likely lose enough steam to preclude organized severe storms.
Either way, gusty winds will be the primary hazard.
LONG TERM
(Sunday Night through next Saturday) Issued at 1051 AM CDT Sat Sep 5 2026
Unfortunately, this heat is not leaving the forecast any time soon.
LREF suggests the midlevel ridge to set right back up over the southeastern CONUS next week, pretty much maxing out the 500 mb height climatology for early September.
While this airmass isn't going to be nearly as humid, we still have forecast highs in the low to mid 90s well into next weekend.
This is almost 10 degrees above normal.
PoPs remain low (<15%) until Thursday and Friday as another cold (read: still hot) front sweeps through.
No big temperature dip behind the front into the weekend, just less humidity.