Alert archive / Nebraska / Flash Flood Watches in 2018

Flash Flood Watch 3, NWS Omaha, NE

June 20, 20186 counties in Nebraska; 4 counties in Iowa

NWS Omaha, NE issued this flash flood watch at Jun 20, 2018, 4:30 AM CDT for 6 counties in Nebraska; 4 counties in Iowa. It took effect at Jun 20, 2018, 1:00 PM CDT. It was in force for 15 hr.

The area

The counties it named.

The facts

Issued
Jun 20, 2018, 4:30 AM CDT (09:30 UTC)
In effect from
Jun 20, 2018, 1:00 PM CDT
Expired
Jun 21, 2018, 4:11 AM CDT
In force
15 hr
Issued by
NWS Omaha, NE
Flood severity
None

Counties Harrison County, IA, Monona County, IA, Pottawattamie County, IA, Shelby County, IA, Burt County, NE, Cedar County, NE, Cuming County, NE, Knox County, NE, Thurston County, NE, Wayne County, NE

The radar

The Omaha radar (KOAX), 77 km from the middle of the area, began a volume at 09:29 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

Omaha, NE (KOAX), launched 00:00Z, 9.5 hours before the alert went out and 77 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, Omaha, NE at 00:00Z on 2018-06-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1806 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, Omaha, NE at 00:00Z on 2018-06-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 16 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
1806 J/kg
Mixed-layer CIN
-39 J/kg
Mixed-layer LCL
818 m above ground
0-6 km bulk shear
24 kt
0-1 km storm-relative helicity
16 m²/s²
0-3 km storm-relative helicity
64 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.1

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 Omaha, NE wrote its last area forecast discussion before this flash flood watch went out at Jun 20, 3:58 AM CDT, 32 minutes earlier.

Area forecast discussion, Jun 20, 3:58 AM CDT, 32 minutes before
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Hazardous weather outlook, Jun 19, 10:46 PM CDT, 5 hours 44 minutes before
Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
1046 PM CDT Tue Jun 19 2018

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-201800-
Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont-
Page-Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison-
Stanton-Cuming-Burt-Platte-Colfax-Dodge-Washington-Butler-
Saunders-Douglas-Sarpy-Seward-Lancaster-Cass-Otoe-Saline-
Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson-
1046 PM CDT Tue Jun 19 2018

This Hazardous Weather Outlook is for portions of southwest
Iowa...west central Iowa...east central Nebraska...northeast
Nebraska and southeast Nebraska.

.DAY ONE...Tonight and Wednesday

Some strong thunderstorms will occur across much of eastern
Nebraska and southwest Iowa overnight, with areas of heavy rain.
Flooding could develop in areas that received over 3 inches of
rain Monday night and Tuesday morning. A flash flood watch is in
effect for portions of the area. A few storms may be severe with
damaging winds and hail.

Thunderstorms will be possible again Wednesday, but the intensity
is expected to be weaker.

.DAYS TWO THROUGH SEVEN...Wednesday night through Tuesday

Thunderstorm chances will remain in the forecast Wednesday night
into Thursday night. Occasional periods of heavy rain are
possible. Thunderstorm chances return to part of the area Saturday
and Saturday night and continue into early next week.

.SPOTTER INFORMATION STATEMENT...

Storm spotter activation is not expected to be needed overnight
or on Wednesday, but please pass along any reports of severe
weather or flooding.

In the hours before

Local storm report, Jun 19, 10:30 PM CDT, 6 hours before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1030 PM CDT TUE JUN 19 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1030 PM     HEAVY RAIN       1 N FAIRBURY            40.15N 97.18W
06/19/2018  M3.20 INCH       JEFFERSON          NE   EMERGENCY MNGR

&&

HD
Special weather statement, Jun 19, 11:09 PM CDT, 5 hours 21 minutes before
Special Weather Statement
National Weather Service Omaha/Valley Nebraska
1109 PM CDT TUE JUN 19 2018

IAZ055-056-069-079-080-090-091-200445-
Pottawattamie IA-Mills IA-Page IA-Fremont IA-Montgomery IA-Shelby IA-
Harrison IA-
1109 PM CDT TUE JUN 19 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN FREMONT...WESTERN
MONTGOMERY...MILLS...POTTAWATTAMIE...SOUTHEASTERN HARRISON...WESTERN
SHELBY AND NORTHWESTERN PAGE COUNTIES UNTIL 1145 PM CDT...

At 1109 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 3 miles southwest of Logan to 6 miles northwest
of Treynor to 7 miles northwest of Sidney. Movement was east at 30
mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Eastern Council Bluffs, Glenwood, Shenandoah, Missouri Valley, Logan,
Oakland, Malvern, Treynor, Underwood, Carson, Essex, Shelby, Minden,
Emerson, Persia, Macedonia, Woodbine, Tabor, Neola and Crescent.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4185 9546 4069 9525 4077 9573 4168 9593
TIME...MOT...LOC 0409Z 263DEG 27KT 4163 9585 4128 9571 4082 9575

SMITH

The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jun 19, 7:15 PM CDTAreal Flood AdvisoryOAXLancaster3 hr
Jun 19, 7:47 PM CDTAreal Flood AdvisoryOAXSeward3 hr
Jun 19, 7:56 PM CDTAreal Flood AdvisoryOAXJefferson64 min
Jun 19, 8:48 PM CDTFlash Flood WarningOAXJefferson6 hr
Jun 19, 9:20 PM CDTSpecial Weather StatementOAXSaunders25 min
Jun 19, 11:13 PM CDTAreal Flood AdvisoryOAXGage5 hr
Jun 19, 11:24 PM CDTAreal Flood AdvisoryOAXCass, Douglas, Sarpy5 hr
Jun 19, 11:29 PM CDTFlash Flood WarningOAXWashington4 hr
Jun 20, 12:58 AM CDTRiver Flood WarningOAXOtoe37 hr
Jun 20, 2:39 AM CDTAreal Flood WarningOAXJefferson6 hr
Jun 20, 10:16 AM CDTRiver Flood WarningOAXCass24 hr
Jun 20, 10:25 AM CDTRiver Flood WarningOAXPierce23 hr
Jun 20, 10:41 AM CDTAreal Flood AdvisoryOAXJefferson5 hr
Jun 20, 6:22 PM CDTRiver Flood WarningOAXSaunders31 hr
Jun 19, 9:47 PM CDTSpecial Weather StatementOAXMontgomery43 min
Jun 19, 9:53 PM CDTAreal Flood AdvisoryOAXMills, Pottawattamie5 hr
Jun 19, 11:09 PM CDTSpecial Weather StatementOAXHarrison, Mills, Pottawattamie36 min

Nearby

Flash Flood Watches in Nebraska, 2018Flash 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.