Alert archive / Arkansas / Mesoscale Discussions in 2021

Mesoscale Discussion 464

April 28, 202128 counties in Arkansas

The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 10:22 PM CDT for 28 counties in Arkansas. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Apr 28, 2021, 10:22 PM CDT (03:22 UTC)
Expired: Apr 29, 2021, 12:15 AM CDT
In force: 113 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch possible
Chance of a watch: 60%

All 28 counties

Cleburne County, AR, Conway County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Faulkner County, AR, Independence County, AR, Izard County, AR, Jackson County, AR, Johnson County, AR, Lawrence County, AR, Lee County, AR, Lonoke County, AR, Mississippi County, AR, Monroe County, AR, Perry County, AR, Poinsett County, AR, Pope County, AR, Prairie County, AR, Pulaski County, AR, Saline County, AR, Searcy County, AR, St. Francis County, AR, Stone County, AR, Van Buren County, AR, White County, AR, Woodruff County, AR, Yell County, AR

The radar

The Little Rock radar (KLZK), 76 km from the middle of the area, began a volume at 03:24 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.

Tornado Watch 123Apr 29, 2:00 AM CDT

The nearest sounding before it

Little Rock, AR (KLZK), launched 00:00Z, 3.4 hours before the alert went out and 182 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.

582 
ACUS11 KWNS 290322
SWOMCD
SPC MCD 290322 
TNZ000-ARZ000-MSZ000-MOZ000-290515-

Mesoscale Discussion 0464
NWS Storm Prediction Center Norman OK
1022 PM CDT Wed Apr 28 2021

Areas affected...Central and Northern Arkansas

Concerning...Severe potential...Watch possible 

Valid 290322Z - 290515Z

Probability of Watch Issuance...60 percent

SUMMARY...A severe threat is expected to develop across parts of
north-central and northeast Arkansas over the next few hours. A
tornado threat along with large hail and wind damage will be
possible. New weather watch issuance may be needed.

DISCUSSION...The latest radar imagery from Little Rock showed a
cluster of strong to severe thunderstorms just to the east of Fort
Smith. This cluster is located along an axis of moderate instability
where MLCAPE is estimated by the RAP in the 1000 to 1500 J/kg range.
The axis of instability extends eastward across north-central
Arkansas to near the Mississippi River. Wind shear along this
corridor is characterized by strong veering winds with height in the
low to mid-levels and 50 knots of southwest flow around 6 km above
ground level. This will be favorable for a tornado threat with
supercells that track eastward near the instability axis. The threat
is expected to develop to the east of WW 121. For that reason, a new
watch may need to be issued.

..Broyles/Guyer.. 04/29/2021

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

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

LAT...LON   35999014 35598998 35049022 34679078 34629192 34569288
            34619342 34879368 35239369 35739341 36019288 36119228
            36109124 36079058 35999014

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 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 29, 3:14 AM CDT	Mesoscale Discussion	SPC	Clay, Craighead, Greene	3 hr

Nearby

Mesoscale Discussions in Arkansas, 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.