Alert archive / Illinois / Areal Flood Advisories in 2021

Areal Flood Advisory 75, NWS St. Louis, MO

August 8, 2021Ralls County, Missouri; Adams County, Pike County, Illinois

NWS St. Louis, MO issued this areal flood advisory at Aug 8, 2021, 4:35 PM CDT for Ralls County, Missouri; Adams County, Pike County, Illinois. It was in force for 3 hr.

The area

The counties it named.

The facts

Issued
Aug 8, 2021, 4:35 PM CDT (21:35 UTC)
Expired
Aug 8, 2021, 7:45 PM CDT
In force
3 hr
Issued by
NWS St. Louis, MO
Area
Storm-based polygon

Counties Adams County, IL, Pike County, IL, Ralls County, MO

The radar

The St Louis radar (KLSX), 121 km from the middle of the area, began a volume at 21:35 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, 9.6 hours before the alert went out and 220 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 2021-08-08Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 567 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 2021-08-08The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 51 square meters per square second.193958Sfc1 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
567 J/kg
Mixed-layer CIN
-127 J/kg
Mixed-layer LCL
1067 m above ground
0-6 km bulk shear
18 kt
0-1 km storm-relative helicity
51 m²/s²
0-3 km storm-relative helicity
-8 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this areal flood 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 areal flood advisory went out at Aug 8, 4:30 PM CDT, 5 minutes earlier.

Area forecast discussion, Aug 8, 4:30 PM CDT, 5 minutes before
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Hazardous weather outlook, Aug 8, 3:02 PM CDT, 1 hour 33 minutes before
Hazardous Weather Outlook
National Weather Service Saint Louis MO
302 PM CDT Sun Aug 8 2021

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-092015-
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-Saint Francois MO-Saint Louis City MO-Saint Louis MO-
Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO-
302 PM CDT Sun Aug 8 2021

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

.DAY ONE...Tonight.

Thunderstorms are likely through tonight. A few of the thunderstorms
through this evening could be severe, with large hail and damaging
winds being the main threats. Locally heavy rainfall will also be
possible this afternoon into tonight, which could result in isolated
instances of flash flooding.

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

Heat index readings will be in the 100 to 110 degree range over parts
of the area during the afternoon and early evening hours from Monday
into Thursday. A heat advisory is now in effect for much of the area
on Monday.

There is a chance for thunderstorms over portions of the area
from Monday through Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed through tonight.

Britt

In the hours before

Local storm report, Aug 8, 3:24 PM CDT, 1 hour 11 minutes before
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Local storm report, Aug 8, 4:09 PM CDT, 26 minutes before
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Local storm report, Aug 8, 4:23 PM CDT, 12 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, 2:37 PM CDTHeat AdvisoryLSXAudrain, Boone, Callaway, Cole, Crawford, Franklin and 23 more4 days
Aug 8, 2:43 PM CDTSevere Thunderstorm WarningLSXFranklin, Gasconade47 min
Aug 8, 3:19 PM CDTSevere Thunderstorm WarningLSXFranklin, Lincoln, Saint Charles, Warren41 min
Aug 8, 3:54 PM CDTSevere Thunderstorm WarningLSXLincoln, Saint Charles66 min
Aug 8, 2:54 PM CDTSevere Thunderstorm WarningLSXAdams, Brown, Pike50 min

Nearby

Areal Flood Advisories in Illinois, 2021Areal Flood Advisories in Missouri, 2021Every areal flood 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.