Alert archive / Illinois / Flash Flood Warnings in 2019

Flash Flood Warning 19, NWS Chicago, IL

September 27, 2019LaSalle County, Livingston County, Illinois

NWS Chicago, IL issued this flash flood warning at Sep 27, 2019, 1:37 PM CDT for LaSalle County, Livingston County, Illinois. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Sep 27, 2019, 1:37 PM CDT (18:37 UTC)
Expired
Sep 27, 2019, 5:44 PM CDT
In force
4 hr
Issued by
NWS Chicago, IL
Area
Storm-based polygon
Flood severity
None

Counties LaSalle County, IL, Livingston County, IL

The radar

The Chicago radar (KLOT), 76 km from the middle of the area, began a volume at 18:39 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, 6.6 hours before the alert went out and 108 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 2019-09-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 2019-09-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 326 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1629 m above ground
0-6 km bulk shear
37 kt
0-1 km storm-relative helicity
326 m²/s²
0-3 km storm-relative helicity
409 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 warning 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 flash flood warning went out at Sep 27, 12:56 PM CDT, 41 minutes earlier.

Area forecast discussion, Sep 27, 12:56 PM CDT, 41 minutes before
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Hazardous weather outlook, Sep 27, 1:37 PM CDT, 0 minutes before
Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
137 PM CDT Fri Sep 27 2019

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
281845-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-Cook-
La Salle-Kendall-Grundy-Will-Kankakee-Livingston-Iroquois-Ford-
Lake IN-Porter-Newton-Jasper-Benton-
137 PM CDT Fri Sep 27 2019 /237 PM EDT Fri Sep 27 2019/

This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.

.DAY ONE...This Afternoon and Tonight.

Weather hazards expected...

  Elevated Thunderstorm Risk...with an associated:
  Elevated hail risk...up to quarter size.
  Limited damaging wind risk...up to 60 mph.
  Significant Flooding Risk.
  High Swim Risk Late Tonight.

DISCUSSION...

The first band of showers and thunderstorms is moving through the
area early this afternoon. Backbuilding storms have developed
along and south of I-80, with the most concentrated area from
Pontiac to Kankakee to Valparaiso. Flash flooding is the highest
concern along this corridor initially. The severe threat is
lower, but some winds to 40 to 45 mph or some small hail is also
possible.

A cold front will bring showers and thunderstorms to the area this
evening. More widespread rainfall is expected, and the concern
for flash flooding may expand a bit farther north toward the
I-80 and I-88 corridor. In addition, some stronger to severe
thunderstorms will be possible mainly later afternoon and evening.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Saturday...
  Limited Flooding Risk.
  Limited Thunderstorm Risk.
  High Swim Risk
Sunday...
  Limited Thunderstorm Risk.
  High Swim Risk
Monday and Tuesday...
  Limited Thunderstorm Risk.
Wednesday and Thursday...
  Limited Thunderstorm Risk.
  High Swim Risk

DISCUSSION:

Strong northeast winds will generate high waves causing strong
rip currents and dangerous swim conditions to area beaches.

.SPOTTER INFORMATION STATEMENT...

  Spotters may be needed this afternoon through this evening.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the northeast at 40 to 45 mph.

LMZ740>745-281845-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
137 PM CDT Fri Sep 27 2019

This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.

.DAY ONE...This Afternoon and Tonight.

Weather hazards expected...

  Hazardous conditions for small craft.
  Elevated Thunderstorm Risk...with an associated:
     Limited hail risk...up to quarter size.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Saturday and Sunday...
  Hazardous conditions for small craft are likely.
  Limited Thunderstorm Risk.
Monday and Tuesday...
  Limited Thunderstorm Risk.
Wednesday and Thursday...
  Hazardous conditions for small craft are likely.
  Limited Thunderstorm Risk.

KMD

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In the hours before

Local storm report, Sep 27, 11:58 AM CDT, 1 hour 39 minutes before
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Special weather statement, Sep 27, 12:28 PM CDT, 1 hour 9 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Sep 27, 9:45 AM CDTRiver Flood AdvisoryLOTOgle12 hr
Sep 27, 1:08 PM CDTAreal Flood AdvisoryLOTGrundy, LaSalle, Livingston3 hr
Sep 27, 1:18 PM CDTSpecial Marine WarningLOT117 min
Sep 27, 1:43 PM CDTFlash Flood WatchLOTDeKalb, DuPage, Ford, Grundy, Iroquois, Kane and 6 more16 hr
Sep 27, 3:15 PM CDTSevere Thunderstorm WarningLOTGrundy, LaSalle, Livingston30 min
Sep 27, 3:16 PM CDTSmall Craft AdvisoryLOT52 hr
Sep 27, 4:04 PM CDTAreal Flood AdvisoryLOTGrundy, LaSalle, Livingston3 hr
Sep 27, 4:15 PM CDTSpecial Weather StatementLOTKankakee15 min
Sep 27, 4:41 PM CDTSpecial Weather StatementLOTLivingston19 min
Sep 27, 5:02 PM CDTSpecial Weather StatementLOTLivingston13 min
Sep 27, 5:31 PM CDTAreal Flood AdvisoryLOTGrundy, Kendall, LaSalle, Will116 min
Sep 27, 5:52 PM CDTAreal Flood AdvisoryLOTCook, Will93 min
Sep 27, 6:11 PM CDTSevere Thunderstorm WarningLOTKankakee, Will34 min
Sep 27, 6:30 PM CDTSevere Thunderstorm WarningLOTLaSalle45 min
Sep 27, 6:42 PM CDTSevere Thunderstorm WarningLOTKankakee, Will36 min
Sep 27, 6:50 PM CDTAreal Flood AdvisoryLOTGrundy, Kankakee, Will4 hr

Nearby

Flash Flood Warnings in Illinois, 2019Every flash flood warning in 2019

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.