Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 290
The Storm Prediction Center issued this mesoscale discussion at Mar 27, 2021, 7:58 PM CDT for 22 counties in Illinois; Ballard County, Kentucky; 11 counties in Missouri. It was in force for 92 min.
The area
The outline as issued.
The facts
- Issued
- Mar 27, 2021, 7:58 PM CDT (00:58 UTC)
- Expired
- Mar 27, 2021, 9:30 PM CDT
- In force
- 92 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 62
All 34 counties
Alexander County, IL, Clay County, IL, Clinton County, IL, Edwards County, IL, Effingham County, IL, Franklin County, IL, Hamilton County, IL, Jackson County, IL, Jefferson County, IL, Johnson County, IL, Marion County, IL, Perry County, IL, Pulaski County, IL, Randolph County, IL, Richland County, IL, Saint Clair County, IL, Saline County, IL, Union County, IL, Washington County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Ballard County, KY, Bollinger County, MO, Butler County, MO, Cape Girardeau County, MO, Carter County, MO, Madison County, MO, Perry County, MO, Saint Francois County, MO, Sainte Genevieve County, MO, Scott County, MO, Stoddard County, MO, Wayne County, MO
The radar
The Paducah radar (KPAH), 92 km from the middle of the area, began a volume at 01:02 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
Lincoln, IL (KILX), launched 00:00Z, 1.0 hours before the alert went out and 296 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
- 933 m above ground
- 0-6 km bulk shear
- 86 kt
- 0-1 km storm-relative helicity
- -3 m²/s²
- 0-3 km storm-relative helicity
- 202 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
690
ACUS11 KWNS 280058
SWOMCD
SPC MCD 280058
INZ000-ILZ000-KYZ000-MOZ000-280230-
Mesoscale Discussion 0290
NWS Storm Prediction Center Norman OK
0758 PM CDT Sat Mar 27 2021
Areas affected...Southeast Missouri and Southern Illinois
Concerning...Severe Thunderstorm Watch 62...
Valid 280058Z - 280230Z
The severe weather threat for Severe Thunderstorm Watch 62
continues.
SUMMARY...Storms moving through WW 62 continue to pose a threat for
large hail and damaging winds. A watch extension or new watch may be
needed.
DISCUSSION...Storms that formed earlier across portions of eastern
Missouri have crossed the Mississippi River and entered portions of
southern Illinois and intensified a bit, with embedded supercell
structures present. Given the background environment characterized
by MLCAPE of 1000-1500 J/kg and effective bulk shear exceeding 60
kt, large hail and damaging winds remain the primary hazards.
Improving low-level shear may foster an isolated tornado threat, at
least while supercell modes can be maintained.
Farther south, convection is now intensifying along the advancing
cold front across far southeast Missouri. A linear mode convection
seems likely, posing a threat for damaging wind gusts, though
embedded supercell structures may materialized with time.
Short-term convection-allowing model trends suggest the environment
may stabilize considerably by 03z-04z. However, it seems likely that
severe storms will continue into portions of southern Illinois.
Thus, a watch extension or new watch may need to be considered
downstream of WW 62.
..Karstens.. 03/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PAH...ILX...LSX...SGF...
LAT...LON 36619028 36839137 38618986 39228833 38358783 36988905
36619028SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 27, 8:19 PM CDT | Severe Thunderstorm Watch | SPC | Clay, Crawford, Edwards, Franklin, Gallatin, Hamilton and 13 more | 114 min |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Missouri, 2021Mesoscale Discussions in Kentucky, 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.