Alert archive / Missouri / Flash Flood Watches in 2020

Flash Flood Watch 11, NWS St. Louis, MO

August 13, 202014 counties in Missouri; 14 counties in Illinois

NWS St. Louis, MO issued this flash flood watch at Aug 13, 2020, 9:49 AM CDT for 14 counties in Missouri; 14 counties in Illinois. It took effect at Aug 13, 2020, 11:00 AM CDT. It was in force for 8 hr.

The area

The counties it named.

The facts

Issued: Aug 13, 2020, 9:49 AM CDT (14:49 UTC)
In effect from: Aug 13, 2020, 11:00 AM CDT
Expired: Aug 13, 2020, 7:00 PM CDT
In force: 8 hr
Issued by: NWS St. Louis, MO
Flood severity: None

All 28 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, Crawford County, 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), 45 km from the middle of the area, began a volume at 14:52 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, 2.8 hours before the alert went out and 232 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: 285 J/kg
Mixed-layer CIN: -225 J/kg
Mixed-layer LCL: 984 m above ground
0-6 km bulk shear: 6 kt
0-1 km storm-relative helicity: 10 m²/s²
0-3 km storm-relative helicity: 13 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 flash flood watch 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 flash flood watch went out at Aug 13, 6:46 AM CDT, 3 hours 3 minutes earlier.

Area forecast discussion, Aug 13, 6:46 AM CDT, 3 hours 3 minutes before

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Hazardous weather outlook, Aug 13, 3:50 AM CDT, 5 hours 59 minutes before

Hazardous Weather Outlook
National Weather Service Saint Louis MO
350 AM CDT Thu Aug 13 2020

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-140900-
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-
350 AM CDT Thu Aug 13 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.

There is a chance for thunderstorms today across parts of southeast
Missouri and southwest Illinois. Storms will be slow moving and
capable of producing localized heavy rainfall and flash flooding.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

There is a chance for thunderstorms across parts of the area Friday
and Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report rainfall amounts greater than 1
inch.

Elmore

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 12, 7:03 PM CDT	Areal Flood Advisory	LSX	Madison	3 hr
Aug 13, 12:17 PM CDT	Flash Flood Warning	LSX	Monroe, Randolph, Saint Clair	6 hr

Nearby

Flash Flood Watches in Missouri, 2020 Flash Flood Watches in Illinois, 2020 Every flash flood watch 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.