Alert archive / Iowa / Flash Flood Watches in 2018

Flash Flood Watch 8, NWS Quad Cities, IA

September 4, 201819 counties in Iowa; 7 counties in Illinois

NWS Quad Cities, IA issued this flash flood watch at Sep 4, 2018, 3:56 AM CDT for 19 counties in Iowa; 7 counties in Illinois. It took effect at Sep 4, 2018, 7:00 PM CDT. It was in force for 24 hr.

The area

The counties it named.

The facts

Issued: Sep 4, 2018, 3:56 AM CDT (08:56 UTC)
In effect from: Sep 4, 2018, 7:00 PM CDT
Expired: Sep 5, 2018, 7:01 PM CDT
In force: 24 hr
Issued by: NWS Quad Cities, IA
Flood severity: None

All 26 counties

Benton County, IA, Buchanan County, IA, Cedar County, IA, Clinton County, IA, Delaware County, IA, Des Moines County, IA, Dubuque County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Linn County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Washington County, IA, Carroll County, IL, Henry County, IL, Jo Daviess County, IL, Mercer County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL

The radar

The Quad Cities radar (KDVN), 42 km from the middle of the area, began a volume at 08:56 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 00:00Z, 8.9 hours before the alert went out and 48 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: 463 J/kg
Mixed-layer CIN: -58 J/kg
Mixed-layer LCL: 1273 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 111 m²/s²
0-3 km storm-relative helicity: 194 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.6

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 Quad Cities, IA wrote its last area forecast discussion before this flash flood watch went out at Sep 4, 3:39 AM CDT, 17 minutes earlier.

Area forecast discussion, Sep 4, 3:39 AM CDT, 17 minutes before

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Hazardous weather outlook, Sep 3, 3:48 PM CDT, 12 hours 8 minutes before

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
348 PM CDT Mon Sep 3 2018

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-042100-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
348 PM CDT Mon Sep 3 2018

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A flash flood watch is in effect through this evening for much of
the outlook area, and there is also a low risk for severe storms.
The main threats will be possible flash flooding and localized
damaging wind.

Area rivers are experiencing flooding. Please see the
latest Flood Statements and Flood Warnings for details.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Tuesday night through Saturday night: More rounds of thunderstorms
can be expected during this time frame. Heavy rainfall and
possible flash flooding will continue to be a concern. The
remnants of tropical system "Gordon" will then track into the
Midwest from the Gulf Coast and cause very heavy rainfall and
flash flooding, along with additional river flooding.

.SPOTTER INFORMATION STATEMENT...

There is a low chance that spotter activation will be needed
through this evening. However, any reports of new flooding or
flash flooding would be appreciated.

Haase

In the hours before

Local storm report, Sep 3, 9:56 PM CDT, 6 hours before

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Special weather statement, Sep 3, 10:01 PM CDT, 5 hours 55 minutes before

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Local storm report, Sep 3, 10:25 PM CDT, 5 hours 31 minutes before

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Local storm report, Sep 3, 11:00 PM CDT, 4 hours 56 minutes before

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The office that day

Everything else NWS Quad Cities, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 3, 7:41 PM CDT	Special Weather Statement	DVN	Benton, Buchanan, Iowa, Linn	64 min
Sep 3, 8:54 PM CDT	Special Weather Statement	DVN	Benton, Buchanan, Delaware, Linn	66 min
Sep 3, 9:28 PM CDT	River Flood Warning	DVN	Jackson	70 hr
Sep 3, 9:28 PM CDT	River Flood Warning	DVN	Benton, Linn	7 days
Sep 3, 10:01 PM CDT	Special Weather Statement	DVN	Buchanan, Delaware	74 min
Sep 4, 11:21 AM CDT	River Flood Warning	DVN	Muscatine, Scott	9 days
Sep 4, 11:21 AM CDT	River Flood Warning	DVN	Muscatine	11 days
Sep 4, 11:21 AM CDT	River Flood Warning	DVN	Louisa, Muscatine	12 days
Sep 4, 11:21 AM CDT	River Flood Warning	DVN	Lee	12 days
Sep 4, 2:16 PM CDT	River Flood Warning	DVN	Jackson	17 hr

Nearby

Flash Flood Watches in Iowa, 2018 Flash Flood Watches in Illinois, 2018 Every flash flood watch 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.