Alert archive / Illinois / Flash Flood Watches in 2017

Flash Flood Watch 4, NWS Chicago, IL

July 20, 201712 counties in Illinois

NWS Chicago, IL issued this flash flood watch at Jul 20, 2017, 2:15 PM CDT for 12 counties in Illinois. It took effect at Jul 21, 2017, 4:00 PM CDT. It was in force for 16 hr.

The area

The counties it named.

The facts

Issued: Jul 20, 2017, 2:15 PM CDT (19:15 UTC)
In effect from: Jul 21, 2017, 4:00 PM CDT
Expired: Jul 22, 2017, 7:53 AM CDT
In force: 16 hr
Issued by: NWS Chicago, IL
Flood severity: None

Counties Boone County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Winnebago County, IL

The radar

The Chicago radar (KLOT), 59 km from the middle of the area, began a volume at 19:17 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, 7.3 hours before the alert went out and 156 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: 591 J/kg
Mixed-layer CIN: -160 J/kg
Mixed-layer LCL: 1436 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 336 m²/s²
0-3 km storm-relative helicity: 429 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.0

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 Chicago, IL wrote its last area forecast discussion before this flash flood watch went out at Jul 20, 12:42 PM CDT, 1 hour 33 minutes earlier.

Area forecast discussion, Jul 20, 12:42 PM CDT, 1 hour 33 minutes before

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Hazardous weather outlook, Jul 20, 1:19 PM CDT, 56 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 19, 7:21 PM CDT	Severe Thunderstorm Warning	LOT	Ogle, Winnebago	54 min
Jul 19, 7:54 PM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Lee, McHenry, Ogle, Winnebago	51 min
Jul 19, 8:05 PM CDT	Special Marine Warning	LOT		25 min
Jul 19, 8:16 PM CDT	Tornado Warning	LOT	Boone, DeKalb, Ogle, Winnebago	29 min
Jul 19, 8:24 PM CDT	Special Marine Warning	LOT		2 hr
Jul 19, 8:30 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, LaSalle, Lee	30 min
Jul 19, 8:34 PM CDT	Severe Thunderstorm Warning	LOT	Boone, Cook, DeKalb, DuPage, Kane, Kendall and 4 more	56 min
Jul 19, 9:08 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Grundy, Kendall, Will	67 min
Jul 19, 9:55 PM CDT	Special Weather Statement	LOT	Kankakee	35 min
Jul 19, 10:26 PM CDT	Special Marine Warning	LOT		64 min
Jul 19, 10:37 PM CDT	Special Weather Statement	LOT	Ford, Iroquois	53 min
Jul 19, 10:49 PM CDT	Special Weather Statement	LOT	Boone, DeKalb, Kane, Lake, McHenry, Winnebago	56 min
Jul 20, 3:28 AM CDT	Special Weather Statement	LOT	Boone, Ogle, Winnebago	47 min
Jul 20, 3:48 AM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Ogle, Winnebago	42 min
Jul 20, 4:21 AM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Kane, Ogle	39 min
Jul 20, 4:38 AM CDT	Special Weather Statement	LOT	Lee, Ogle	52 min
Jul 20, 6:47 AM CDT	Special Weather Statement	LOT	DeKalb, LaSalle, Lee	43 min
Jul 20, 7:14 AM CDT	Areal Flood Advisory	LOT	Cook, DuPage, Kane, Kendall, Lake, Will	2 hr
Jul 20, 7:21 AM CDT	River Flood Advisory	LOT	Winnebago	7 days
Jul 20, 7:21 AM CDT	River Flood Advisory	LOT	Ogle	5 days
Jul 20, 7:21 AM CDT	River Flood Advisory	LOT	Lee	66 hr
Jul 20, 7:27 AM CDT	Special Weather Statement	LOT	Grundy, Kendall, LaSalle, Livingston	48 min
Jul 20, 8:15 AM CDT	River Flood Warning	LOT	Cook	5 days
Jul 20, 9:23 AM CDT	River Flood Watch	LOT	Winnebago	24 hr
Jul 20, 9:30 AM CDT	River Flood Advisory	LOT	Boone	4 days
Jul 20, 9:30 AM CDT	River Flood Advisory	LOT	Winnebago	52 hr
Jul 20, 9:30 AM CDT	River Flood Advisory	LOT	Winnebago	7 days
Jul 20, 9:30 AM CDT	River Flood Advisory	LOT	Winnebago	7 days
Jul 20, 2:51 PM CDT	River Flood Warning	LOT	Winnebago	6 days
Jul 20, 2:51 PM CDT	River Flood Warning	LOT	Winnebago	19 days

Nearby

Flash Flood Watches in Illinois, 2017 Every flash flood watch in 2017

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.