Alert archive / Illinois / Flash Flood Warnings in 2018

Flash Flood Warning 30, NWS St. Louis, MO

August 17, 2018Montgomery County, Illinois

NWS St. Louis, MO issued this flash flood warning at Aug 17, 2018, 1:19 AM CDT for Montgomery County, Illinois. It was in force for 6 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 17, 2018, 1:19 AM CDT (06:19 UTC)
Expired
Aug 17, 2018, 7:15 AM CDT
In force
6 hr
Issued by
NWS St. Louis, MO
Area
Storm-based polygon
Flood severity
None

County Montgomery County, IL

The radar

The Lincoln radar (KILX), 103 km from the middle of the area, began a volume at 06:22 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 00:00Z, 6.3 hours before the alert went out and 121 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 00:00Z on 2018-08-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2444 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lincoln, IL at 00:00Z on 2018-08-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 74 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
2444 J/kg
Mixed-layer CIN
-1 J/kg
Mixed-layer LCL
939 m above ground
0-6 km bulk shear
26 kt
0-1 km storm-relative helicity
74 m²/s²
0-3 km storm-relative helicity
99 m²/s²
Significant tornado parameter
0.6
Supercell composite
3.1

Open this sounding in Storm Lab

The text

As transmitted.

376 
WGUS53 KLSX 170619
FFWLSX
ILC135-171215-
/O.NEW.KLSX.FF.W.0030.180817T0619Z-180817T1215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service St Louis MO
119 AM CDT FRI AUG 17 2018

The National Weather Service in St Louis has issued a

* Flash Flood Warning for...
  Montgomery County in south central Illinois...

* Until 715 AM CDT.

* At 119 AM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Two to three inches of rain 
  has already fallen. Flash flooding is expected to begin shortly.

* Some locations that will experience flooding include...
  Litchfield, Hillsboro, Nokomis, Witt, Taylor Springs, Schram City,
  Irving, Coalton, Butler, Ohlman, Walshville, Wenonah and Honey
  Bend.

This includes Interstate 55 in Illinois between exits 52 and 60.
 
This also includes Lake Lou Yaeger.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

&&

LAT...LON 3922 8925 3914 8925 3904 8970 3928 8970
      3935 8931 3935 8914 3922 8914

$$

Tilly
2 follow-up statements
195 
WGUS73 KLSX 170928
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
428 AM CDT FRI AUG 17 2018

ILC135-171215-
/O.CON.KLSX.FF.W.0030.000000T0000Z-180817T1215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery IL-
428 AM CDT FRI AUG 17 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 715 AM CDT FOR
MONTGOMERY COUNTY...

At 425 AM CDT, automated river gauges indicated flooding is 
occurring along the East Fork Shoal Creek near Coffeen. Up to three 
inches of rain have already fallen across the warned area. 

Some locations that will experience flooding include...
Litchfield, Hillsboro, Nokomis, Witt, Taylor Springs, Schram City,
Irving, Coalton, Butler, Ohlman, Walshville, Wenonah and Honey Bend.

This includes Interstate 55 in Illinois between exits 52 and 60.
 
This also includes Lake Lou Yaeger.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

&&

LAT...LON 3922 8925 3914 8925 3904 8970 3928 8970
      3935 8931 3935 8914 3922 8914

$$

Tilly
836 
WGUS73 KLSX 171214
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
714 AM CDT FRI AUG 17 2018

ILC135-171223-
/O.EXP.KLSX.FF.W.0030.000000T0000Z-180817T1215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery IL-
714 AM CDT FRI AUG 17 2018

...THE FLASH FLOOD WARNING FOR MONTGOMERY COUNTY WILL EXPIRE AT 715
AM CDT...

The heavy rain has ended. Flood waters have receded. Flooding is no
longer expected to pose a threat. Please continue to heed any
remaining road closures.

LAT...LON 3922 8925 3914 8925 3904 8970 3928 8970
      3935 8931 3935 8914 3922 8914

$$

GKS

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 16, 10:41 PM CDTSpecial Weather StatementLSXGreene34 min
Aug 17, 12:36 AM CDTSpecial Weather StatementLSXMontgomery39 min
Aug 17, 1:55 AM CDTSevere Thunderstorm WarningLSXBond, Fayette, Montgomery35 min
Aug 17, 2:31 AM CDTFlash Flood WarningLSXFayette5 hr
Aug 17, 2:50 AM CDTSpecial Weather StatementLSXMarion40 min

Nearby

Flash Flood Warnings in Illinois, 2018Every flash flood warning 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.