Alert archive / Illinois / Heat Advisories in 2020

Heat Advisory 4, NWS St. Louis, MO

August 9, 202013 counties in Missouri; 14 counties in Illinois

NWS St. Louis, MO issued this heat advisory at Aug 9, 2020, 1:54 PM CDT for 13 counties in Missouri; 14 counties in Illinois. It took effect at Aug 10, 2020, 12:00 PM CDT. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued
Aug 9, 2020, 1:54 PM CDT (18:54 UTC)
In effect from
Aug 10, 2020, 12:00 PM CDT
Expired
Aug 10, 2020, 7:00 PM CDT
In force
7 hr
Issued by
NWS St. Louis, MO
All 27 counties

Bond County, IL, Calhoun County, IL, Clinton County, IL, Fayette County, IL, Greene County, IL, Jersey County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Monroe County, IL, Montgomery County, IL, Randolph County, IL, Saint Clair County, IL, Washington County, IL, City of Saint Louis, MO, Franklin County, MO, Iron County, MO, Jefferson County, MO, Lincoln County, MO, Madison County, MO, Reynolds County, MO, Saint Charles County, MO, Saint Francois County, MO, Saint Louis County, MO, Sainte Genevieve County, MO, Warren County, MO, Washington County, MO

The radar

The St Louis radar (KLSX), 47 km from the middle of the area, began a volume at 18:56 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

Lincoln, IL (KILX), launched 12:00Z, 6.9 hours before the alert went out and 229 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 2020-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 221 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 2020-08-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -48 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
221 J/kg
Mixed-layer CIN
-272 J/kg
Mixed-layer LCL
941 m above ground
0-6 km bulk shear
7 kt
0-1 km storm-relative helicity
-48 m²/s²
0-3 km storm-relative helicity
8 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

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 St. Louis, MO wrote its last area forecast discussion before this heat advisory went out at Aug 9, 12:55 PM CDT, 59 minutes earlier.

Area forecast discussion, Aug 9, 12:55 PM CDT, 59 minutes before
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Hazardous weather outlook, Aug 9, 4:24 AM CDT, 9 hours 30 minutes before
Hazardous Weather Outlook
National Weather Service Saint Louis MO
424 AM CDT Sun Aug 9 2020

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-100930-
Adams IL-Audrain MO-Bond IL-Boone MO-Brown IL-Calhoun IL-Callaway MO-
Clinton IL-Cole MO-Crawford MO-Fayette IL-Franklin MO-Gasconade MO-
Greene IL-Iron MO-Jefferson MO-Jersey IL-Knox MO-Lewis MO-Lincoln MO-
Macoupin IL-Madison IL-Madison MO-Marion IL-Marion MO-Moniteau MO-
Monroe IL-Monroe MO-Montgomery IL-Montgomery MO-Osage MO-Pike IL-
Pike MO-Ralls MO-Randolph IL-Reynolds MO-Saint Charles MO-
Saint Clair IL-Saint Francois MO-Saint Louis City MO-Saint Louis MO-
Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO-
424 AM CDT Sun Aug 9 2020

This Hazardous Weather Outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Today and tonight.

Numerous thunderstorms are expected this morning in eastern Missouri
and southwestern Illinois. Heavy rainfall is likely, which may
result in flash flooding through the morning. A Flash Flood Watch is
in effect through the morning.

Isolated severe thunderstorms are possible this evening and
overnight, primarily across northeastern Missouri and west-central
Illinois.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Dangerous heat is possible on Monday afternoon, with heat index
values of 100-105 degrees in east-central and southeastern Missouri
as well as southwestern Illinois.

There is a chance of isolated severe thunderstorms Monday.
Thunderstorms are possible Tuesday through Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed in northeastern Missouri and west-
central Illinois Sunday evening and night and then again Monday
afternoon and evening.

Elmore

In the hours before

Local storm report, Aug 9, 1:28 PM CDT, 26 minutes before
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Local storm report, Aug 9, 1:29 PM CDT, 25 minutes before
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Local storm report, Aug 9, 1:34 PM CDT, 20 minutes before
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Local storm report, Aug 9, 1:44 PM CDT, 10 minutes before
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Local storm report, Aug 9, 1:45 PM CDT, 9 minutes before
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Local storm report, Aug 9, 1:49 PM CDT, 5 minutes before
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The office that day

Everything else NWS St. Louis, MO issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 8, 10:50 PM CDTAreal Flood AdvisoryLSXLincoln, Pike6 hr
Aug 8, 11:03 PM CDTFlash Flood WarningLSXLincoln, Pike6 hr
Aug 9, 12:01 AM CDTFlash Flood WarningLSXSaint Charles6 hr
Aug 9, 12:56 AM CDTAreal Flood AdvisoryLSXSaint Louis3 hr
Aug 9, 1:15 AM CDTRiver Flood WarningLSXSaint Charles22 hr
Aug 9, 1:25 AM CDTFlash Flood WarningLSXSaint Louis6 hr
Aug 9, 2:27 AM CDTAreal Flood AdvisoryLSXSaint Charles, Warren4 hr
Aug 9, 2:41 AM CDTFlash Flood WarningLSXJefferson, Saint Louis, City of Saint Louis6 hr
Aug 9, 3:54 AM CDTAreal Flood AdvisoryLSXFranklin, Gasconade4 hr
Aug 9, 7:29 AM CDTAreal Flood WarningLSXSaint Louis3 hr
Aug 9, 9:55 AM CDTAreal Flood AdvisoryLSXMadison, Saint Clair3 hr
Aug 9, 10:06 AM CDTFlash Flood WarningLSXMadison4 hr
Aug 9, 10:23 AM CDTFlash Flood WarningLSXSaint Clair4 hr
Aug 9, 2:07 PM CDTAreal Flood WarningLSXSaint Clair3 hr

Nearby

Heat Advisories in Illinois, 2020Heat Advisories in Missouri, 2020Every heat advisory in 2020

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.