Alert archive / Illinois / Mesoscale Discussions in 2018

Mesoscale Discussion 1381

August 28, 201817 counties in Illinois

The Storm Prediction Center issued this mesoscale discussion at Aug 28, 2018, 3:42 PM CDT for 17 counties in Illinois. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued
Aug 28, 2018, 3:42 PM CDT (20:42 UTC)
Expired
Aug 28, 2018, 5:15 PM CDT
In force
93 min
Issued by
the Storm Prediction Center
Chance of a watch
40%

Counties Bureau County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Marshall County, IL, Peoria County, IL, Putnam County, IL, Stark County, IL, Will County, IL, Woodford County, IL

The radar

The Chicago radar (KLOT), 68 km from the middle of the area, began a volume at 20:45 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

Davenport, (KDVN), launched 12:00Z, 8.7 hours before the alert went out and 142 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, Davenport, at 12:00Z on 2018-08-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 955 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, Davenport, at 12:00Z on 2018-08-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 360 square meters per square second.19395878Sfc1 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
955 J/kg
Mixed-layer CIN
-230 J/kg
Mixed-layer LCL
1046 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
360 m²/s²
0-3 km storm-relative helicity
487 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.8

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 28, 12:14 PM CDTMesoscale DiscussionSPCJo Daviess2 hr
Aug 28, 5:06 PM CDTSevere Thunderstorm WatchSPCAdams, Bureau, Carroll, Fulton, Hancock, Henderson and 17 more6 hr

Nearby

Mesoscale Discussions in Illinois, 2018Every mesoscale discussion in 2018

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.