Alert archive / Iowa / Flash Flood Watches in 2018

Flash Flood Watch 10, NWS Des Moines, IA

September 4, 201828 counties in Iowa

NWS Des Moines, IA issued this flash flood watch at Sep 4, 2018, 3:33 AM CDT for 28 counties in Iowa. It took effect at Sep 4, 2018, 1:00 PM CDT. It was in force for 18 hr.

The area

The counties it named.

The facts

Issued
Sep 4, 2018, 3:33 AM CDT (08:33 UTC)
In effect from
Sep 4, 2018, 1:00 PM CDT
Expired
Sep 5, 2018, 7:00 AM CDT
In force
18 hr
Issued by
NWS Des Moines, IA
Flood severity
None
All 28 counties

Black Hawk County, IA, Boone County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Cerro Gordo County, IA, Dallas County, IA, Emmet County, IA, Franklin County, IA, Grundy County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Humboldt County, IA, Jasper County, IA, Kossuth County, IA, Marshall County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Sac County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winnebago County, IA, Worth County, IA, Wright County, IA

The radar

The Des Moines radar (KDMX), 89 km from the middle of the area, began a volume at 08:35 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

Minneapolis, MN (KMPX), launched 00:00Z, 8.6 hours before the alert went out and 258 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, Minneapolis, MN at 00:00Z on 2018-09-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 55 joules per kilogram.LCLLFCEL10008507005003002001001 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, Minneapolis, MN at 00:00Z on 2018-09-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 5 square meters per square second.19395878Sfc1 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
55 J/kg
Mixed-layer CIN
-10 J/kg
Mixed-layer LCL
600 m above ground
0-6 km bulk shear
13 kt
0-1 km storm-relative helicity
5 m²/s²
0-3 km storm-relative helicity
7 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 Des Moines, IA wrote its last area forecast discussion before this flash flood watch went out at Sep 4, 12:05 AM CDT, 3 hours 28 minutes earlier.

Area forecast discussion, Sep 4, 12:05 AM CDT, 3 hours 28 minutes before
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Hazardous weather outlook, Sep 3, 3:32 PM CDT, 12 hours 1 minute before
Hazardous Weather Outlook
National Weather Service Des Moines IA
332 PM CDT Mon Sep 3 2018

IAZ004>007-015>017-023>025-033>035-044-045-057-042045-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Sac-Calhoun-Webster-Crawford-Carroll-
Audubon-
332 PM CDT Mon Sep 3 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Periods of thunderstorms with heavy rain will occur through
tonight. Severe storms are not expected but heavy rainfall may
cause within bank rises of streams and rivers and localized flash
flooding.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

While occasional strong thunderstorms may be possible at times,
the main concern will be for periods of very heavy rainfall.
Portions of central and northern Iowa are the likeliest to see the
heaviest rainfall amounts Tuesday evening and overnight with
amounts well in excess of 2 inches likely for some.

With very heavy rainfall expected, river flooding and flash flood
threats will increase significantly during those time periods.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected though severe weather and
rainfall reports are appreciated.

IAZ026>028-036>039-046>050-058>062-070>075-081>086-092>097-042045-
Franklin-Butler-Bremer-Hamilton-Hardin-Grundy-Black Hawk-Greene-
Boone-Story-Marshall-Tama-Guthrie-Dallas-Polk-Jasper-Poweshiek-
Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-Clarke-Lucas-
Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-Appanoose-Davis-
332 PM CDT Mon Sep 3 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

A flash flood watch is in effect for the area, please visit
www.weather.gov/desmoines for more details.

Periods of thunderstorms with heavy rainfall will occur through
tonight. Due to heavy rainfall the past few nights, many local
streams and rivers are rising towards or above bankfull and could
go into flood. In addition, soils are saturated and runoff from
more rain could cause flash flooding. Flash flooding and other
flooding headlines, including river floods, may be necessary.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

While occasional strong thunderstorms may be possible at times,
the main concern will be for periods of very heavy rainfall.
Portions of central and northern Iowa are the likeliest to see the
heaviest rainfall amounts Tuesday evening and overnight with
amounts well in excess of 2 inches likely for some.

With very heavy rainfall expected, river flooding and flash flood
threats will increase significantly during those time periods.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected though severe weather and
rainfall reports are appreciated.

CURTIS

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 3, 7:32 PM CDTSpecial Weather StatementDMXBlack Hawk, Bremer, Grundy88 min
Sep 3, 7:43 PM CDTFlash Flood WarningDMXBlack Hawk3 hr
Sep 4, 9:34 AM CDTRiver Flood WatchDMXCerro Gordo, Floyd, Worth13 hr
Sep 4, 9:34 AM CDTRiver Flood WatchDMXBlack Hawk, Bremer, Butler25 hr
Sep 4, 2:21 PM CDTSevere Thunderstorm WarningDMXPalo Alto, Pocahontas14 min
Sep 4, 3:46 PM CDTTornado Warning Tornado observedDMXKossuth29 min
Sep 4, 4:45 PM CDTTornado WarningDMXHancock, Winnebago30 min
Sep 4, 5:09 PM CDTFlash Flood WarningDMXHancock, Kossuth, Winnebago6 hr

Nearby

Flash Flood Watches in Iowa, 2018Every 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.