Alert archive / Illinois / Mesoscale Discussions in 2021

Mesoscale Discussion 1009

June 19, 20217 counties in Illinois

The Storm Prediction Center issued this mesoscale discussion at Jun 19, 2021, 11:15 AM CDT for 7 counties in Illinois. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jun 19, 2021, 11:15 AM CDT (16:15 UTC)
Expired: Jun 19, 2021, 1:15 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Effingham County, IL, Fayette County, IL, Greene County, IL, Macoupin County, IL, Montgomery County, IL, Morgan County, IL, Scott County, IL

The radar

The Lincoln radar (KILX), 94 km from the middle of the area, began a volume at 16:17 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.

Severe Thunderstorm Watch 287Jun 19, 2:40 PM CDT

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 4.3 hours before the alert went out and 129 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1960 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 142 m²/s²
0-3 km storm-relative helicity: 203 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

982 
ACUS11 KWNS 191616
SWOMCD
SPC MCD 191615 
ILZ000-191815-

Mesoscale Discussion 1009
NWS Storm Prediction Center Norman OK
1115 AM CDT Sat Jun 19 2021

Areas affected...parts of central and south-central IL

Concerning...Severe potential...Watch unlikely 

Valid 191615Z - 191815Z

Probability of Watch Issuance...20 percent

SUMMARY...A mesoscale area of hail potential will seemingly focus
over parts of central and south-central IL through the midday hours.
There is relatively large uncertainty in the evolution of this small
thunderstorm cluster beyond 1pm.

DISCUSSION...Radar mosaic shows several outflows from overnight
thunderstorm complexes over the OH Valley trailing westward into the
mid MS Valley.  An area of stronger thunderstorm cores has developed
over central IL late this morning on the western periphery of the
influence of the thunderstorm cluster near the IN/KY border. 
Surface temperatures at 11am are relatively mild (low to mid 70s deg
F) owing to some cloud debris but clearing skies will enable
stronger heating to occur downstream of the central IL thunderstorm
cluster.  It is unclear whether this convection will remain elevated
or transition to surface based over the next few hours.  It is this
uncertainty, coupled with differing model guidance, that lends
question to the potential spatial extent of severe thunderstorm
activity this afternoon.  Nonetheless, it appears ample flow exists
across this region to support organized storms (reference the St.
Louis WSR-88D VAD data).  Given the limited spatial extent of the
ongoing strong to severe thunderstorms over central IL late this
morning, this will likely preclude a severe thunderstorm watch
issuance.  However, convective trends will continue to be monitored
over the next few hours for a possible greater-than-expected severe
risk.

..Smith/Hart.. 06/19/2021

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

ATTN...WFO...ILX...LSX...

LAT...LON   39879041 39168847 38818838 38688873 39419083 39709070
            39879041

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 18, 8:53 PM CDT	Mesoscale Discussion	SPC	Bond, Brown, Cass, Christian, Clark, Clay and 26 more	97 min
Jun 18, 9:20 PM CDT	Severe Thunderstorm Watch	SPC	Cass, Champaign, Christian, Clark, Clay, Coles and 33 more	7 hr
Jun 18, 9:27 PM CDT	Mesoscale Discussion	SPC	Adams, Brown, Hancock, Henderson, McDonough, Mercer and 2 more	2 hr
Jun 18, 10:08 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Brown, Bureau, Hancock, Henderson, Henry and 6 more	8 hr
Jun 19, 2:10 AM CDT	Mesoscale Discussion	SPC	Adams, Brown, Cass, Champaign, Christian, Clark and 27 more	2 hr
Jun 19, 2:12 PM CDT	Mesoscale Discussion	SPC	Bond, Calhoun, Clinton, Greene, Jersey, Macoupin and 7 more	93 min
Jun 19, 2:43 PM CDT	Severe Thunderstorm Watch	SPC	Bond, Calhoun, Clinton, Fayette, Greene, Jersey and 9 more	7 hr
Jun 19, 5:11 PM CDT	Mesoscale Discussion	SPC	Calhoun, Clinton, Greene, Jersey, Macoupin, Madison and 6 more	64 min

Nearby

Mesoscale Discussions in Illinois, 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.