Alert archive / Kentucky / Mesoscale Discussions in 2021
Mesoscale Discussion 518
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 1:17 AM CDT for 25 counties in Kentucky; 9 counties in Tennessee. It was in force for 118 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 1:17 AM CDT (06:17 UTC)
- Expired
- May 4, 2021, 3:15 AM CDT
- In force
- 118 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 34 counties
Adair County, KY, Allen County, KY, Barren County, KY, Butler County, KY, Christian County, KY, Clinton County, KY, Cumberland County, KY, Daviess County, KY, Edmonson County, KY, Grayson County, KY, Green County, KY, Hart County, KY, Hopkins County, KY, Logan County, KY, McCreary County, KY, McLean County, KY, Metcalfe County, KY, Monroe County, KY, Muhlenberg County, KY, Ohio County, KY, Russell County, KY, Simpson County, KY, Todd County, KY, Warren County, KY, Wayne County, KY, Clay County, TN, Cumberland County, TN, Fentress County, TN, Jackson County, TN, Macon County, TN, Overton County, TN, Pickett County, TN, Sumner County, TN, Trousdale County, TN
The radar
The Nashville radar (KOHX), 94 km from the middle of the area, began a volume at 06:16 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Nashville Metro, TN (KBNA), launched 00:00Z, 6.3 hours before the alert went out and 107 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 2263 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 1050 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 119 m²/s²
- 0-3 km storm-relative helicity
- 193 m²/s²
- Significant tornado parameter
- 1.3
- Supercell composite
- 7.6
The text
As transmitted.
861
ACUS11 KWNS 040617
SWOMCD
SPC MCD 040617
KYZ000-TNZ000-INZ000-040815-
Mesoscale Discussion 0518
NWS Storm Prediction Center Norman OK
0117 AM CDT Tue May 04 2021
Areas affected...portions of southern and western Kentucky into
northern Middle Tennessee
Concerning...Severe potential...Watch unlikely
Valid 040617Z - 040815Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated severe storms -- capable of producing hail up to
about 1.5" in diameter -- will continue over the next couple of
hours.
DISCUSSION...Latest radar data shows scattered thunderstorms which
have gradually increased in coverage over the past 1 to 2 hours from
western Kentucky into northern Middle Tennessee. The storms are
occurring within an area of weak QG forcing ahead of a subtle vort
max crossing the area, aided by substantial elevated CAPE/steep
mid-level lapse rates. Moderate flow aloft is sufficient for
isolated stronger updrafts, and while the elevated nature of the
convection suggests only limited wind risk, large hail will remain
possible with stronger cells.
..Goss/Guyer.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MRX...JKL...LMK...OHX...PAH...
LAT...LON 36938430 35908488 36268575 36768762 37428772 37828732
37688614 36938430SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 1:06 AM CDT | Mesoscale Discussion | SPC | Ballard, Caldwell, Calloway, Carlisle, Christian, Crittenden and 13 more | 114 min |
| May 4, 1:41 AM CDT | Severe Thunderstorm Watch | SPC | Ballard, Caldwell, Calloway, Carlisle, Christian, Crittenden and 13 more | 6 hr |
| May 4, 4:17 AM CDT | Mesoscale Discussion | SPC | Adair, Allen, Ballard, Barren, Butler, Caldwell and 25 more | 88 min |
| May 4, 5:13 AM CDT | Severe Thunderstorm Watch | SPC | Adair, Allen, Barren, Butler, Clinton, Cumberland and 11 more | 5 hr |
| May 4, 7:31 AM CDT | Mesoscale Discussion | SPC | Anderson, Bedford, Bledsoe, Bradley, Campbell, Cannon and 33 more | 89 min |
| May 4, 8:37 AM CDT | Severe Thunderstorm Watch | SPC | Anderson, Blount, Bradley, Jefferson, Knox, Loudon and 7 more | 3 hr |
| May 4, 11:58 AM CDT | Mesoscale Discussion | SPC | Fayette, Hardeman, McNairy, Shelby | 2 hr |
Nearby
Mesoscale Discussions in Kentucky, 2021Mesoscale Discussions in Tennessee, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.