Alert archive / Tennessee / Mesoscale Discussions in 2021

Mesoscale Discussion 554

May 6, 20214 states

The Storm Prediction Center issued this mesoscale discussion at May 6, 2021, 2:45 PM CDT for 4 states. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: May 6, 2021, 2:45 PM CDT (19:45 UTC)
Expired: May 6, 2021, 4:15 PM CDT
In force: 90 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 152

All 27 counties

Clay County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Greene County, AR, Mississippi County, AR, Poinsett County, AR, Carlisle County, KY, Fulton County, KY, Hickman County, KY, Dunklin County, MO, Mississippi County, MO, New Madrid County, MO, Pemiscot County, MO, Scott County, MO, Stoddard County, MO, Crockett County, TN, Dyer County, TN, Gibson County, TN, Haywood County, TN, Lake County, TN, Lauderdale County, TN, Madison County, TN, Obion County, TN, Shelby County, TN, Tipton County, TN, Weakley County, TN

The radar

The Memphis radar (KNQA), 96 km from the middle of the area, began a volume at 19:46 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

Little Rock, AR (KLZK), launched 12:00Z, 7.8 hours before the alert went out and 154 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1745 m above ground
0-6 km bulk shear: 76 kt
0-1 km storm-relative helicity: 47 m²/s²
0-3 km storm-relative helicity: 88 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

444 
ACUS11 KWNS 061946
SWOMCD
SPC MCD 061945 
TNZ000-KYZ000-ILZ000-MOZ000-ARZ000-062115-

Mesoscale Discussion 0554
NWS Storm Prediction Center Norman OK
0245 PM CDT Thu May 06 2021

Areas affected...Far Southeast MO/MO Bootheel...Far Western
KY...Western TN...Northwest AR

Concerning...Severe Thunderstorm Watch 152...

Valid 061945Z - 062115Z

The severe weather threat for Severe Thunderstorm Watch 152
continues.

SUMMARY...Threat for isolated hail and damaging wind gusts continues
across much of the region.

DISCUSSION...Updrafts within the much of the convective cluster
moving across the Mid MS Valley have recently shown a deepening
trend. Some modest increase in forward progression is also occurring
with this portion of the line, with storm motion now around 35-40
kt. Given this speed, the more southward moving portion (along the
far southern edge of this cluster) will likely move outside the
current watch around 20Z. In contrast to the rest of the cluster,
this portion has been weakening over the past half hour, suggesting
the severe threat may not extend past the edge of the watch. A more
easterly motion is anticipated with the rest of the cluster, bring
it to the edge of the watch in TN closer to 21Z. 

A narrow corridor of better low-level moisture (i.e. dewpoints in
the mid 40s) only extends through western TN, with dewpoints still
in the upper 30s across much of middle TN. This may limit the
intensity as the cluster moves east into more of middle TN late this
afternoon and evening. However, the environment where the cluster
currently resides is supportive of strong to severe storms capable
of isolated hail and damaging wind gusts.

..Mosier.. 05/06/2021

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

ATTN...WFO...PAH...MEG...LZK...

LAT...LON   37188959 37038897 36158841 35518883 35049033 35369117
            36149085 37188959

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 6, 10:05 AM CDT	Mesoscale Discussion	SPC	Clay, Crittenden, Mississippi	85 min
May 6, 12:02 PM CDT	Mesoscale Discussion	SPC	Clay, Craighead, Greene, Lawrence, Mississippi, Randolph	118 min
May 6, 12:38 PM CDT	Severe Thunderstorm Watch	SPC	Clay, Craighead, Crittenden, Cross, Greene, Jackson and 4 more	5 hr
May 6, 9:52 AM CDT	Mesoscale Discussion	SPC	Crawford, Dent, Franklin, Gasconade, Iron, Jefferson and 17 more	83 min
May 6, 5:11 PM CDT	Mesoscale Discussion	SPC	Bedford, Cannon, Cheatham, Coffee, Davidson, Franklin and 18 more	94 min

Nearby

Mesoscale Discussions in Tennessee, 2021 Mesoscale Discussions in Arkansas, 2021 Mesoscale Discussions in Missouri, 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.