Alert archive / Kentucky / Mesoscale Discussions in 2021

Mesoscale Discussion 467

April 29, 20215 states

The Storm Prediction Center issued this mesoscale discussion at Apr 29, 2021, 3:14 AM CDT for 5 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 29, 2021, 3:14 AM CDT (08:14 UTC)
Expired: Apr 29, 2021, 6:15 AM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 40 counties

Clay County, AR, Craighead County, AR, Greene County, AR, Alexander County, IL, Gallatin County, IL, Hardin County, IL, Johnson County, IL, Massac County, IL, Pope County, IL, Pulaski County, IL, Saline County, IL, Union County, IL, Williamson County, IL, Ballard County, KY, Caldwell County, KY, Calloway County, KY, Carlisle County, KY, Crittenden County, KY, Fulton County, KY, Graves County, KY, Hickman County, KY, Livingston County, KY, Lyon County, KY, Marshall County, KY, McCracken County, KY, Union County, KY, Webster County, KY, Bollinger County, MO, Butler County, MO, Cape Girardeau County, MO, Dunklin County, MO, Mississippi County, MO, New Madrid County, MO, Pemiscot County, MO, Ripley County, MO, Scott County, MO, Stoddard County, MO, Wayne County, MO, Lake County, TN, Obion County, TN

The radar

The Paducah radar (KPAH), 100 km from the middle of the area, began a volume at 08:14 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 00:00Z, 8.2 hours before the alert went out and 203 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: 703 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 907 m above ground
0-6 km bulk shear: 63 kt
0-1 km storm-relative helicity: 241 m²/s²
0-3 km storm-relative helicity: 341 m²/s²
Significant tornado parameter: 1.2
Supercell composite: 12.0

Open this sounding in Storm Lab

The text

As transmitted.

838 
ACUS11 KWNS 290814
SWOMCD
SPC MCD 290814 
KYZ000-INZ000-ILZ000-TNZ000-MOZ000-ARZ000-291115-

Mesoscale Discussion 0467
NWS Storm Prediction Center Norman OK
0314 AM CDT Thu Apr 29 2021

Areas affected...Missouri Bootheel region...lower Ohio River Valley

Concerning...Severe potential...Watch unlikely 

Valid 290814Z - 291115Z

Probability of Watch Issuance...20 percent

SUMMARY...Locally strong wind gusts are possible from far northeast
Arkansas toward the lower Ohio River Valley, but severe coverage is
not expected to warrant a watch.

DISCUSSION...An MCV is evident on radar over northeast AR and
straddling the MO border, ahead of a weak cold front. Dewpoints of
63-67 F are common east/northeast of the MCV and as far north as
southern IL. Though moist, this yields only a few hundred J/kg of
MUCAPE per SFCOA due to weak lapse rates.

Southwesterly 850 mb flow of 40-50 kt is likely to persist tonight
ahead of the cold front, and below moderate mid and high level
winds. Veering winds with height and good deep-layer shear is thus
conditionally favorable for severe storms, and shear may be locally
enhanced near the MCV. However, the limited instability is expected
to minimize overall threat. A few strong wind gusts will be possible
in association with the MCV convection, but a watch is unlikely.

..Jewell.. 04/29/2021

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

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

LAT...LON   35579147 35809105 36009087 36339082 36559093 36759103
            37119053 37878920 38008847 37918795 37468753 36908777
            36538838 36208900 35908992 35579147

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 28, 7:55 PM CDT	Tornado Watch	SPC	Clark, Cleburne, Conway, Crawford, Faulkner, Franklin and 18 more	6 hr
Apr 28, 9:19 PM CDT	Mesoscale Discussion	SPC	Crawford, Franklin, Howard, Little River, Logan, Montgomery and 5 more	116 min
Apr 28, 10:22 PM CDT	Mesoscale Discussion	SPC	Cleburne, Conway, Craighead, Crittenden, Cross, Faulkner and 22 more	113 min
Apr 29, 1:09 AM CDT	Mesoscale Discussion	SPC	Hempstead, Howard, Little River, Logan, Miller, Montgomery and 6 more	2 hr
Apr 29, 2:01 AM CDT	Tornado Watch	SPC	Clark, Conway, Faulkner, Garland, Hempstead, Hot Spring and 17 more	6 hr
Apr 28, 7:25 PM CDT	Mesoscale Discussion	SPC	Caldwell, Calloway, Christian, Lyon, Marshall, Trigg	65 min

Nearby

Mesoscale Discussions in Kentucky, 2021 Mesoscale Discussions in Missouri, 2021 Mesoscale Discussions in Illinois, 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.