Alert archive / Tennessee / Mesoscale Discussions in 2021

Mesoscale Discussion 142

February 28, 2021Clinton County, Cumberland County, Monroe County, Kentucky; 20 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2021, 8:45 PM CST for Clinton County, Cumberland County, Monroe County, Kentucky; 20 counties in Tennessee. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Feb 28, 2021, 8:45 PM CST (02:45 UTC)
Expired: Feb 28, 2021, 10:15 PM CST
In force: 90 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 15

All 23 counties

Clinton County, KY, Cumberland County, KY, Monroe County, KY, Bedford County, TN, Cannon County, TN, Clay County, TN, Coffee County, TN, Cumberland County, TN, DeKalb County, TN, Fentress County, TN, Grundy County, TN, Jackson County, TN, Macon County, TN, Overton County, TN, Pickett County, TN, Putnam County, TN, Rutherford County, TN, Smith County, TN, Trousdale County, TN, Van Buren County, TN, Warren County, TN, White County, TN, Wilson County, TN

The radar

The Nashville radar (KOHX), 87 km from the middle of the area, began a volume at 02:45 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 nearest sounding before it

Nashville Metro, TN (KBNA), launched 00:00Z, 2.8 hours before the alert went out and 88 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 419 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 979 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: 220 m²/s²
0-3 km storm-relative helicity: 278 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 4.5

Open this sounding in Storm Lab

The text

As transmitted.

721 
ACUS11 KWNS 010245
SWOMCD
SPC MCD 010245 
TNZ000-KYZ000-010415-

Mesoscale Discussion 0142
NWS Storm Prediction Center Norman OK
0845 PM CST Sun Feb 28 2021

Areas affected...Middle Tennessee...Far South-central Kentucky

Concerning...Severe Thunderstorm Watch 15...

Valid 010245Z - 010415Z

The severe weather threat for Severe Thunderstorm Watch 15
continues.

SUMMARY...An isolated severe threat is likely to continue across
parts of WW 15 over then next hour or so. Wind damage and hail will
be the primary threats. These threats are expected to become
marginal and the weather watch will be allowed to expire at 04Z.

DISCUSSION...The latest radar imagery shows a convective cluster
located from middle Tennessee extending northeastward into far
south-central Kentucky. The storms are located along a corridor of
weak instability where the RAP is estimating MLCAPE in the 250 to
500 J/kg range. Despite the weak instability, the Tri Cities WSR-88D
VWP has 0-6 km shear in the 65 to 70 kt range. This suggests that an
isolated severe threat will continue for another hour or two, before
the instability becomes too weak to support cell organization.
Because the threat should become marginal late this evening, the
weather watch will be allowed to expire at 04Z.

..Broyles.. 03/01/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MRX...JKL...LMK...OHX...HUN...

LAT...LON   35318594 35338602 35408619 35368628 35368640 35368654
            35468658 35688663 35768666 36018658 36198658 36398640
            36418635 36578625 36628616 36618608 36668602 36838594
            36898567 36868561 36968544 36968532 36888520 36848507
            36848504 36808498 36648502 36628494 36618481 36568468
            36418469 36358474 36288484 36188485 36108478 35968471
            35858470 35778483 35728502 35768516 35698526 35548542
            35528555 35448555 35358557 35328570 35258573 35318599
            35378603 35388621 35318594

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 28, 7:11 PM CST	Severe Thunderstorm Watch	SPC	Clinton, Cumberland, Monroe	3 hr
Feb 28, 7:16 PM CST	Mesoscale Discussion	SPC	Allen, Clinton, Cumberland, Metcalfe, Monroe, Wayne	59 min
Feb 28, 6:27 PM CST	Mesoscale Discussion	SPC	Benton, Carroll, Cheatham, Chester, Crockett, Davidson and 29 more	93 min

Nearby

Mesoscale Discussions in Tennessee, 2021 Mesoscale Discussions in Kentucky, 2021 Every 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.