Alert archive / Illinois / Heat Advisories in 2021

Heat Advisory 1, NWS Chicago, IL

August 9, 202118 counties in Illinois; 5 counties in Indiana

NWS Chicago, IL issued this heat advisory at Aug 9, 2021, 2:46 PM CDT for 18 counties in Illinois; 5 counties in Indiana. It took effect at Aug 10, 2021, 12:00 PM CDT. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued: Aug 9, 2021, 2:46 PM CDT (19:46 UTC)
In effect from: Aug 10, 2021, 12:00 PM CDT
Expired: Aug 10, 2021, 7:00 PM CDT
In force: 7 hr
Issued by: NWS Chicago, IL

All 23 counties

Boone County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, McHenry County, IL, Ogle County, IL, Will County, IL, Winnebago County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN

The radar

The Chicago radar (KLOT), 12 km from the middle of the area, began a volume at 19:47 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 nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 7.8 hours before the alert went out and 193 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: 1676 J/kg
Mixed-layer CIN: -63 J/kg
Mixed-layer LCL: 705 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 171 m²/s²
0-3 km storm-relative helicity: 208 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.7

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this heat advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Chicago, IL wrote its last area forecast discussion before this heat advisory went out at Aug 9, 12:37 PM CDT, 2 hours 9 minutes earlier.

Area forecast discussion, Aug 9, 12:37 PM CDT, 2 hours 9 minutes before

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Hazardous weather outlook, Aug 9, 12:11 PM CDT, 2 hours 35 minutes before

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In the hours before

Local storm report, Aug 9, 12:11 PM CDT, 2 hours 35 minutes before

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<body>
  <main class="wrap">
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      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
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The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 9, 6:52 AM CDT	Special Weather Statement	LOT	Winnebago	23 min
Aug 9, 11:49 AM CDT	Areal Flood Advisory	LOT	Boone, DeKalb, Kane, McHenry, Ogle, Winnebago	3 hr
Aug 9, 3:14 PM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Ogle, Winnebago	61 min
Aug 9, 3:25 PM CDT	Areal Flood Advisory	LOT	Boone, Winnebago	3 hr
Aug 9, 3:46 PM CDT	Tornado Warning	LOT	Boone, Winnebago	26 min
Aug 9, 4:12 PM CDT	Areal Flood Advisory	LOT	Boone, McHenry	3 hr
Aug 9, 4:34 PM CDT	Tornado Warning Tornado observed	LOT	DeKalb	41 min
Aug 9, 4:39 PM CDT	Tornado Warning	LOT	DeKalb, Ogle	51 min
Aug 9, 5:11 PM CDT	Tornado Warning	LOT	Lee	49 min
Aug 9, 5:15 PM CDT	Tornado Warning	LOT	DeKalb, Kane	60 min
Aug 9, 5:32 PM CDT	Tornado Warning Tornado observed	LOT	DeKalb, Ogle	43 min
Aug 9, 5:42 PM CDT	Tornado Warning	LOT	Kane	48 min
Aug 9, 6:00 PM CDT	Tornado Warning	LOT	DeKalb, Lee	26 min
Aug 9, 6:09 PM CDT	Tornado Warning	LOT	DeKalb, Kane	51 min
Aug 9, 6:24 PM CDT	Tornado Warning	LOT	DuPage, Kane	66 min
Aug 9, 6:45 PM CDT	Special Marine Warning	LOT		90 min
Aug 9, 6:50 PM CDT	Tornado Warning	LOT	Kane	40 min

Nearby

Heat Advisories in Illinois, 2021 Heat Advisories in Indiana, 2021 Every heat advisory 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.