Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 1774
The Storm Prediction Center issued this mesoscale discussion at Sep 21, 2021, 2:47 PM CDT for 7 counties in Arkansas; 4 parishes in Louisiana; 17 counties in Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 21, 2021, 2:47 PM CDT (19:47 UTC)
- Expired
- Sep 21, 2021, 5:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 28 counties
Ashley County, AR, Bradley County, AR, Chicot County, AR, Desha County, AR, Drew County, AR, Lincoln County, AR, Union County, AR, East Carroll Parish, LA, Morehouse Parish, LA, Union Parish, LA, West Carroll Parish, LA, Attala County, MS, Bolivar County, MS, Carroll County, MS, Coahoma County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Leflore County, MS, Montgomery County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Washington County, MS, Yalobusha County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 150 km from the middle of the area, began a volume at 19:48 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
Jackson, MS (KJAN), launched 12:00Z, 7.8 hours before the alert went out and 141 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
- 1083 J/kg
- Mixed-layer CIN
- -19 J/kg
- Mixed-layer LCL
- 723 m above ground
- 0-6 km bulk shear
- 12 kt
- 0-1 km storm-relative helicity
- -10 m²/s²
- 0-3 km storm-relative helicity
- -14 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.1
The text
As transmitted.
938
ACUS11 KWNS 211947
SWOMCD
SPC MCD 211947
MSZ000-ARZ000-LAZ000-212215-
Mesoscale Discussion 1774
NWS Storm Prediction Center Norman OK
0247 PM CDT Tue Sep 21 2021
Areas affected...portions of extreme southeast Arkansas into far
northeast Louisiana and northwest Mississippi
Concerning...Severe potential...Watch unlikely
Valid 211947Z - 212215Z
Probability of Watch Issuance...5 percent
SUMMARY...A damaging gust or two remains possible, particularly with
the more organized line segments. The overall severe threat appears
too sparse and brief to warrant a WW issuance.
DISCUSSION...Pulse cellular storms have congealed into loosely
organized linear segments over the past couple of hours due to cold
pool mergers. No observations or reports have been received of
damaging gusts so far. However, peak heating is underway, supporting
near 90F surface temperatures and a mixed boundary layer,
contributing to 2000+ J/kg MLCAPE. As such, a damaging gust or two
cannot be ruled out with the more potent water-loaded storm cores.
Nonetheless, damaging gusts should remain very isolated and brief,
precluding a WW issuance.
..Squitieri/Hart.. 09/21/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LZK...SHV...
LAT...LON 33339280 34059176 34469066 34359005 34148972 33758956
33168953 32858958 32649025 32519092 32529137 32549188
32699235 32879275 33339280SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 21, 11:51 AM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Bradley, Calhoun, Chicot, Clark and 23 more | 2 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Arkansas, 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.