Alert archive / Arkansas / Mesoscale Discussions in 2021
Mesoscale Discussion 1773
The Storm Prediction Center issued this mesoscale discussion at Sep 21, 2021, 11:51 AM CDT for 29 counties in Arkansas; 5 parishes in Louisiana; 19 counties in Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 21, 2021, 11:51 AM CDT (16:51 UTC)
- Expired
- Sep 21, 2021, 2:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 53 counties
Arkansas County, AR, Ashley County, AR, Bradley County, AR, Calhoun County, AR, Chicot County, AR, Clark County, AR, Cleveland County, AR, Columbia County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Grant County, AR, Hempstead County, AR, Hot Spring County, AR, Jefferson County, AR, Lafayette County, AR, Lee County, AR, Lincoln County, AR, Lonoke County, AR, Miller County, AR, Monroe County, AR, Nevada County, AR, Ouachita County, AR, Phillips County, AR, Prairie County, AR, Pulaski County, AR, Saline County, AR, St. Francis County, AR, Union County, AR, Claiborne Parish, LA, East Carroll Parish, LA, Morehouse Parish, LA, Union Parish, LA, West Carroll Parish, LA, Bolivar County, MS, Carroll County, MS, Coahoma County, MS, DeSoto County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Leflore County, MS, Montgomery County, MS, Panola County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tunica County, MS, Washington County, MS, Yalobusha County, MS
The radar
The Little Rock radar (KLZK), 136 km from the middle of the area, began a volume at 16:51 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, 4.9 hours before the alert went out and 185 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
- 1459 J/kg
- Mixed-layer CIN
- -33 J/kg
- Mixed-layer LCL
- 745 m above ground
- 0-6 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- -23 m²/s²
- 0-3 km storm-relative helicity
- -40 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.9
The text
As transmitted.
406
ACUS11 KWNS 211652
SWOMCD
SPC MCD 211651
MSZ000-TNZ000-ARZ000-LAZ000-TXZ000-211915-
Mesoscale Discussion 1773
NWS Storm Prediction Center Norman OK
1151 AM CDT Tue Sep 21 2021
Areas affected...portions of central and southern Arkansas into
western Mississippi
Concerning...Severe potential...Watch unlikely
Valid 211651Z - 211915Z
Probability of Watch Issuance...20 percent
SUMMARY...A couple damaging gusts may accompany the stronger storms.
A WW issuance is not expected given the anticipated isolated, brief
nature of the severe threat.
DISCUSSION...Thunderstorms have been increasing in number and
intensity along the cold front given low-level convergence and ample
diurnal heating. Surface temperatures in the mid to upper 80s F,
coupled with mid to upper 70s F dewpoints, are currently
contributing to 1000-2000 J/kg MLCAPE despite the relative absence
of appreciable lapse rates. However, as diurnal heating promotes
further heating and boundary-layer mixing, low-level lapse rates
should steadily improve through the afternoon, with further
increases in MLCAPE expected.
A few ongoing storms have already shown up to 35 dBZ cores exceeding
60 kft, and with increasing instability, a greater number of deeper
water-loaded cores are expected. Despite the overall lack of robust
upper support and vertical wind shear ahead of the front,
water-loaded cores may support a couple of damaging gusts through
the afternoon. Nonetheless, given poor shear and brief,
pulse-cellular storm modes, the severe threat is expected to remain
sparse and brief, and a WW issuance appears unlikely.
..Squitieri/Hart.. 09/21/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LZK...SHV...
LAT...LON 33219453 34329332 34929224 35129125 35069027 34808974
34208943 33858941 33218970 32849017 32669086 32669196
32839375 33219453SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 21, 2:47 PM CDT | Mesoscale Discussion | SPC | Ashley, Bradley, Chicot, Desha, Drew, Lincoln and 1 more | 2 hr |
Nearby
Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Louisiana, 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.