Alert archive / Nebraska / Flash Flood Warnings in 2018

Flash Flood Warning 5, NWS Omaha, NE

June 11, 2018Cass County, Sarpy County, Nebraska

NWS Omaha, NE issued this flash flood warning at Jun 11, 2018, 6:31 PM CDT for Cass County, Sarpy County, Nebraska. It was in force for 113 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jun 11, 2018, 6:31 PM CDT (23:31 UTC)
Expired: Jun 11, 2018, 8:24 PM CDT
In force: 113 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Flood severity: None

Counties Cass County, NE, Sarpy County, NE

The radar

The Omaha radar (KOAX), 34 km from the middle of the area, began a volume at 23:31 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.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this flash flood warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.5 hours before the alert went out and 34 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: 1072 J/kg
Mixed-layer CIN: -356 J/kg
Mixed-layer LCL: 1255 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 312 m²/s²
0-3 km storm-relative helicity: 463 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 6.2

Open this sounding in Storm Lab

The text

As transmitted.

782 
WGUS53 KOAX 112331
FFWOAX
NEC025-153-120330-
/O.NEW.KOAX.FF.W.0005.180611T2331Z-180612T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Omaha/Valley Nebraska
631 PM CDT MON JUN 11 2018

The National Weather Service in Omaha has issued a

* Flash Flood Warning for...
  Central Sarpy County in east central Nebraska...
  Northeastern Cass County in southeastern Nebraska...

* Until 1030 PM CDT.

* At 630 PM CDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to three inches of rain have
  already fallen. Flash flooding is expected to begin shortly.

* Some locations that will experience flooding include...
  Springfield, Cedar Creek and Camp Maha. 

Additional rainfall amounts of two inches are possible in the warned 
area.

This includes Interstate 80 in Nebraska between mile markers 435 and
437.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to higher ground now. Act quickly to protect your life.

&&

LAT...LON 4102 9620 4111 9623 4114 9618 4110 9599
      4100 9603

$$

PEARSON

1 follow-up statement

891 
WGUS73 KOAX 120124
FFSOAX

Flash Flood Statement
National Weather Service Omaha/Valley Nebraska
824 PM CDT MON JUN 11 2018

NEC025-153-120133-
/O.CAN.KOAX.FF.W.0005.000000T0000Z-180612T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sarpy NE-Cass NE-
824 PM CDT MON JUN 11 2018

...THE FLASH FLOOD WARNING FOR CENTRAL SARPY AND NORTHEASTERN CASS
COUNTIES IS CANCELLED...

Flood waters have receded. Flooding is no longer expected to pose a
threat. Please continue to heed any remaining road closures.

LAT...LON 4102 9620 4111 9623 4114 9618 4110 9599
      4100 9603

$$

PEARSON

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 Omaha, NE wrote its last area forecast discussion before this flash flood warning went out at Jun 11, 6:27 PM CDT, 4 minutes earlier.

Area forecast discussion, Jun 11, 6:27 PM CDT, 4 minutes before

Area Forecast Discussion
National Weather Service Omaha/Valley NE
627 PM CDT Mon Jun 11 2018

.UPDATE...
Issued at 318 PM CDT Mon Jun 11 2018

Afternoon monitoring continues. Per latest radar imagery, the
surface cold front is now through Wayne, Columbus and York. We
continue to watch the warm front closely as it extends from near
Blair eastward along I-80 in Iowa per satellite imagery and sfc
observations. Convection continues to bubble along this boundary
in western Iowa and will continue to monitor this closely as
backed surface winds enhance low-level hodographs indicating more
tornadic potential in this area. In addition, capping inversion
should continue to erode across eastern Nebraska this afternoon
with steepening mid- level lapse rates spreading overhead.

&&

.SHORT TERM...(Tonight through Thursday)
Issued at 212 PM CDT Mon Jun 11 2018

Main forecast concern is centered around convection this
afternoon/evening.

18Z subjective surface analysis shows a surface cold front extending
southeast from southeastern SD to Grand Island to central KS. As
this cold front continues to push southeast, thunderstorm
initiation is expected along and near the front by mid-afternoon
and storms are expected to continue to drift southeast into the
evening once a fairly decent capping inversion per 19z observed
OAX sounding erodes. A warm/moist airmass in place ahead of the
surface boundary, where surface dewpoints have increased into the
lower to mid 70s, combined with warm temperatures in the upper 80s
to lower 90s, has led to SBCAPE values around 3000-4500 J/kg.
Cooling aloft is expected later this afternoon as a subtle
shortwave trough drives east leading to steepening mid-level lapse
rates through peak heating. All modes of severe wx are possible
despite modest deep layer wind shear.

Activity should move southeast of the CWA by 03-04Z with cooler
and drier conditions behind it. Overnight lows across the area
will range from the low 50s in our north to the low 60s in our
south. Cool and dry conditions are expected Tuesday with southerly
low level flow returning by Wednesday. Instability axis will
remain to our west across central Nebraska/central South Dakota
into Wednesday night. Strong nocturnal low-level jet should allow
convection to commence to our west overnight in the instability
axis and spread east by Thursday morning ahead of a small mid-
level shortwave trough.

.LONG TERM...(Thursday night through Monday)
Issued at 212 PM CDT Mon Jun 11 2018

Southwest flow aloft is expected to begin Thursday as an upper
trough digs across the western states.  This should push high temps
Fri-Sat into the mid-upper 90s. Monsoonal moisture from a tropical
system currently off the Baja will spread northeast into the
Northern Plains, keeping the axis well to our west through the
weekend. A Northern Plains shortwave interacting with this moisture
is progged to push a cold front into the Central Plains late in the
weekend into early next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 622 PM CDT Mon Jun 11 2018

As thunderstorms exit the area this evening behind a cold front,
MVFR conditions are expected for several hours. Northwest surface
winds are expected through the overnight with some patchy fog
possible into the morning.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

UPDATE...Kern
SHORT TERM...Kern
LONG TERM...Kern
AVIATION...Kern

Hazardous weather outlook, Jun 11, 4:43 PM CDT, 1 hour 48 minutes before

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
443 PM CDT Mon Jun 11 2018

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-121145-
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-
443 PM CDT Mon Jun 11 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 Tuesday

Severe thunderstorms are likely this evening across much of
eastern Nebraska and southwest Iowa as a cold front sweeps through
the area. Very large hail, damaging wind gusts and isolated
tornadoes are possible through 9 pm.

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

The next decent chance for thunderstorms will come Wednesday
night, with off-and-on storm chances Thursday through Saturday.

.SPOTTER INFORMATION STATEMENT...

Storm spotter activation will likely be needed through the
evening.

In the hours before

Local storm report, Jun 11, 5:30 PM CDT, 1 hour 1 minute before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
530 PM CDT MON JUN 11 2018

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

0530 PM     HAIL             1 NNE FREMONT           41.45N 96.48W
06/11/2018  M1.00 INCH       DODGE              NE   NWS EMPLOYEE

&&

Local storm report, Jun 11, 5:36 PM CDT, 55 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
536 PM CDT MON JUN 11 2018

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

0536 PM     HAIL             FREMONT                 41.44N 96.50W
06/11/2018  E1.50 INCH       DODGE              NE   TRAINED SPOTTER

&&

Local storm report, Jun 11, 5:37 PM CDT, 54 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
537 PM CDT MON JUN 11 2018

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

0529 PM     HAIL             FREMONT                 41.44N 96.49W
06/11/2018  M1.75 INCH       DODGE              NE   NWS EMPLOYEE

&&

JRB

Local storm report, Jun 11, 5:43 PM CDT, 48 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
543 PM CDT MON JUN 11 2018

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

0510 PM     HAIL             LYONS                   41.94N 96.47W
06/11/2018  M1.00 INCH       BURT               NE   TRAINED SPOTTER

&&

JRB

Local storm report, Jun 11, 6:10 PM CDT, 21 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
610 PM CDT MON JUN 11 2018

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

0610 PM     HAIL             4 NE CEDAR CREEK        41.07N 96.04W
06/11/2018  E1.00 INCH       SARPY              NE   PUBLIC

&&

Local storm report, Jun 11, 6:24 PM CDT, 7 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
624 PM CDT MON JUN 11 2018

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

0500 PM     HAIL             2 ESE GRETNA            41.13N 96.22W
06/11/2018  E1.75 INCH       SARPY              NE   PUBLIC

&&

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 11, 4:31 PM CDT	Severe Thunderstorm Warning	OAX	Colfax, Cuming, Dodge	44 min
Jun 11, 4:36 PM CDT	Severe Thunderstorm Warning	OAX	Burt, Cuming, Thurston	39 min
Jun 11, 4:50 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Douglas, Sarpy	40 min
Jun 11, 5:08 PM CDT	Severe Thunderstorm Warning	OAX	Burt, Cuming, Dodge, Washington	52 min
Jun 11, 5:15 PM CDT	Tornado Warning	OAX	Dodge, Saunders	30 min
Jun 11, 5:24 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Douglas, Sarpy	51 min
Jun 11, 5:28 PM CDT	Tornado Warning	OAX	Cass, Sarpy	32 min
Jun 11, 5:32 PM CDT	Severe Thunderstorm Warning	OAX	Dodge, Douglas, Saunders, Washington	43 min
Jun 11, 5:44 PM CDT	Areal Flood Advisory	OAX	Sarpy	3 hr
Jun 11, 6:00 PM CDT	Tornado Warning	OAX	Cass	30 min
Jun 11, 6:13 PM CDT	Areal Flood Advisory	OAX	Cass, Sarpy	3 hr
Jun 11, 6:13 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Douglas, Sarpy, Saunders	62 min
Jun 11, 6:26 PM CDT	Tornado Warning	OAX	Cass	49 min
Jun 11, 6:35 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Gage, Johnson, Lancaster, Nemaha, Otoe	55 min
Jun 11, 6:40 PM CDT	Tornado Warning	OAX	Cass, Otoe	23 min
Jun 11, 6:58 PM CDT	Tornado Warning	OAX	Otoe	32 min

Nearby

Flash Flood Warnings in Nebraska, 2018 Every flash flood warning 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.