Alert archive / Illinois / Mesoscale Discussions in 2013

Mesoscale Discussion 1815

August 31, 201355 counties in Illinois; 22 counties in Indiana; Saint Louis County, City of Saint Louis, Missouri

The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2013, 2:24 PM CDT for 55 counties in Illinois; 22 counties in Indiana; Saint Louis County, City of Saint Louis, Missouri. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 31, 2013, 2:24 PM CDT (19:24 UTC)
Expired
Aug 31, 2013, 4:30 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 79 counties

Bond County, IL, Calhoun County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, Clark County, IL, Clay County, IL, Clinton County, IL, Coles County, IL, Crawford County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Edgar County, IL, Edwards County, IL, Effingham County, IL, Fayette County, IL, Ford County, IL, Franklin County, IL, Gallatin County, IL, Greene County, IL, Hamilton County, IL, Jackson County, IL, Jasper County, IL, Jefferson County, IL, Jersey County, IL, Lawrence County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Mason County, IL, McLean County, IL, Menard County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Perry County, IL, Piatt County, IL, Randolph County, IL, Richland County, IL, Saint Clair County, IL, Saline County, IL, Sangamon County, IL, Scott County, IL, Shelby County, IL, Tazewell County, IL, Vermilion County, IL, Wabash County, IL, Washington County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Clay County, IN, Daviess County, IN, Dubois County, IN, Fountain County, IN, Gibson County, IN, Greene County, IN, Knox County, IN, Martin County, IN, Monroe County, IN, Montgomery County, IN, Morgan County, IN, Owen County, IN, Parke County, IN, Pike County, IN, Posey County, IN, Putnam County, IN, Sullivan County, IN, Vanderburgh County, IN, Vermillion County, IN, Vigo County, IN, Warren County, IN, Warrick County, IN, City of Saint Louis, MO, Saint Louis County, MO

The radar

The Lincoln radar (KILX), 110 km from the middle of the area, began a volume at 19:25 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 12:00Z, 7.4 hours before the alert went out and 104 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-pSkew-T log-p diagram, Lincoln, IL at 12:00Z on 2013-08-31Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1297 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lincoln, IL at 12:00Z on 2013-08-31The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 88 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
1297 J/kg
Mixed-layer CIN
-160 J/kg
Mixed-layer LCL
1417 m above ground
0-6 km bulk shear
15 kt
0-1 km storm-relative helicity
88 m²/s²
0-3 km storm-relative helicity
14 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 30, 7:10 PM CDTMesoscale DiscussionSPCFord, Grundy, Iroquois, Kankakee, Kendall, LaSalle and 2 more65 min
Aug 30, 8:32 PM CDTMesoscale DiscussionSPCDeKalb, Grundy, Kankakee, Kendall, LaSalle, Lee and 3 more58 min
Aug 31, 3:43 PM CDTSevere Thunderstorm WatchSPCBond, Cass, Champaign, Christian, Clark, Clay and 34 more8 hr
Aug 31, 6:05 PM CDTMesoscale DiscussionSPCBond, Clinton, Jackson, Monroe, Perry, Randolph and 2 more85 min
Aug 31, 6:09 PM CDTMesoscale DiscussionSPCChampaign, Christian, Clark, Coles, Crawford, Cumberland and 17 more66 min

Nearby

Mesoscale Discussions in Illinois, 2013Mesoscale Discussions in Indiana, 2013Mesoscale Discussions in Missouri, 2013Every mesoscale discussion in 2013

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.