Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 474
The Storm Prediction Center issued this mesoscale discussion at May 2, 2021, 3:33 PM CDT for 11 parishes in Louisiana; 22 counties in Mississippi. It was in force for 117 min.
The area
The outline as issued.
The facts
- Issued
- May 2, 2021, 3:33 PM CDT (20:33 UTC)
- Expired
- May 2, 2021, 5:30 PM CDT
- In force
- 117 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 33 counties
Avoyelles Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Richland Parish, LA, Tensas Parish, LA, West Carroll Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Franklin County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Jefferson County, MS, Jefferson Davis County, MS, Lawrence County, MS, Lincoln County, MS, Madison County, MS, Pike County, MS, Rankin County, MS, Sharkey County, MS, Simpson County, MS, Warren County, MS, Washington County, MS, Wilkinson County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 94 km from the middle of the area, began a volume at 20:34 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.
The nearest sounding before it
Jackson, MS (KJAN), launched 12:00Z, 8.6 hours before the alert went out and 87 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1640 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 37 m²/s²
- 0-3 km storm-relative helicity
- 45 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
388
ACUS11 KWNS 022033
SWOMCD
SPC MCD 022033
MSZ000-LAZ000-ARZ000-022230-
Mesoscale Discussion 0474
NWS Storm Prediction Center Norman OK
0333 PM CDT Sun May 02 2021
Areas affected...Northeast Louisiana and Southwestern Mississippi
Concerning...Severe potential...Watch possible
Valid 022033Z - 022230Z
Probability of Watch Issuance...40 percent
SUMMARY...Ongoing thunderstorms across central Louisiana may
intensify in the coming hours as clouds gradually clear over eastern
LA and west/southwest MS. Trends will continue to be monitored, and
a watch is possible in the coming hours.
DISCUSSION...Recent satellite and radar trends show scattered
thunderstorms continue to develop across central LA within a broad
warm frontal zone and just ahead of a mid-level vorticity maximum.
However, convective intensity has generally stagnated, likely due to
a combination of marginal instability (around 500-1000 J/kg MLCAPE),
somewhat shallow mid-level lapse rates (around 6 C/km), and a lack
of stronger low-level forcing for ascent. These storms will likely
remain sub-severe in the near term, but an increase in intensity is
possible further downstream across northeast LA and into western and
southwestern MS. Latest GOES visible imagery shows gradual clearing
across this region, and surface temperatures have responded with
several stations reporting temperatures in the upper 70s and low
80s. This will help augment MLCAPE over the next few hours and may
support gradual intensification. Additionally, regional VWPs show
veering flow within the lowest 2-3 km that could support organized
low-level mesocyclones and a more robust severe threat. A watch is
possible in the coming hours if convective trends begin to show
signs of intensification.
..Moore/Dial.. 05/02/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...LCH...SHV...
LAT...LON 31739234 32369209 32819178 33169134 33409093 33539054
33469008 33158976 32458963 31878964 31488969 31268990
31169042 31109105 31089149 31089201 31159236 31739234SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 2, 1:47 PM CDT | Mesoscale Discussion | SPC | Allen, Beauregard, Bienville, Caldwell, Catahoula, Grant and 8 more | 88 min |
| May 2, 4:46 PM CDT | Tornado Watch | SPC | East Carroll, Madison, Tensas, West Carroll | 5 hr |
| May 2, 6:51 PM CDT | Mesoscale Discussion | SPC | Attala, Calhoun, Carroll, Chickasaw, Choctaw, Clay and 14 more | 54 min |
Nearby
Mesoscale 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.