Alert archive / Nebraska / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 237, NWS Omaha, NE

August 20, 2017Lancaster County, Nebraska

NWS Omaha, NE issued this severe thunderstorm warning at Aug 20, 2017, 5:01 AM CDT for Lancaster County, Nebraska. It was in force for 29 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Aug 20, 2017, 5:01 AM CDT (10:01 UTC)
Expired: Aug 20, 2017, 5:30 AM CDT
In force: 29 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

County Lancaster County, NE

The radar

The Omaha radar (KOAX), 65 km from the middle of the area, began a volume at 10:00 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, 10.0 hours before the alert went out and 65 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: 505 J/kg
Mixed-layer CIN: -393 J/kg
Mixed-layer LCL: 1964 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 153 m²/s²
0-3 km storm-relative helicity: 269 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 severe thunderstorm 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 severe thunderstorm warning went out at Aug 20, 3:33 AM CDT, 1 hour 28 minutes earlier.

Area forecast discussion, Aug 20, 3:33 AM CDT, 1 hour 28 minutes before

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Hazardous weather outlook, Aug 19, 3:45 PM CDT, 13 hours 16 minutes before

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
345 PM CDT Sat Aug 19 2017

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-201045-
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-
345 PM CDT Sat Aug 19 2017

This hazardous weather outlook is for parts of eastern Nebraska
and southwest Iowa.

.DAY ONE...tonight and Sunday.

Scattered thunderstorms are expected to move into the area this
evening and tonight. There is a marginal risk of severe
thunderstorms in much of eastern Nebraska, where large hail and
damaging winds are possible. In western Iowa, storms could produce
small hail and gusty winds. There is also a risk of heavy rain in
some of the storms.

Thunderstorm chances will linger into Sunday. At this time, the
chance of severe storms is low.

.DAYS TWO THROUGH SEVEN...Sunday night through Saturday.

Thunderstorm chances will linger in the forecast from Sunday night
into Tuesday morning. Isolated severe thunderstorms will be
possible on Sunday evening into Sunday night, along with heavy
rain. It appears that the potential for severe storms and heavy
rain will be higher from Monday evening into Monday night.

Much of the mid part of the week from Tuesday night into Friday
should be dry, but thunderstorm chances return by Friday night.

..SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected to be needed tonight or Sunday.

In the hours before

Special weather statement, Aug 20, 1:03 AM CDT, 3 hours 58 minutes before

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Special weather statement, Aug 20, 2:28 AM CDT, 2 hours 33 minutes before

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Special weather statement, Aug 20, 4:14 AM CDT, 47 minutes before

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Special weather statement, Aug 20, 4:36 AM CDT, 25 minutes before

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Special weather statement, Aug 20, 4:52 AM CDT, 9 minutes before

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Special weather statement, Aug 20, 4:54 AM CDT, 7 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 19, 9:55 PM CDT	Special Weather Statement	OAX	Boone	50 min
Aug 19, 10:08 PM CDT	Severe Thunderstorm Warning	OAX	Boone, Madison, Platte	37 min
Aug 19, 10:43 PM CDT	Special Weather Statement	OAX	Colfax	47 min
Aug 19, 10:55 PM CDT	Severe Thunderstorm Warning	OAX	Colfax, Dodge, Saunders	35 min
Aug 19, 11:35 PM CDT	Flash Flood Watch	OAX	Butler, Colfax, Lancaster, Platte, Saline, Saunders and 1 more	7 hr
Aug 19, 11:57 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Sarpy	33 min
Aug 20, 12:21 AM CDT	Special Weather Statement	OAX	Seward	39 min
Aug 20, 1:03 AM CDT	Special Weather Statement	OAX	Gage, Johnson, Lancaster, Otoe	42 min
Aug 20, 2:28 AM CDT	Special Weather Statement	OAX	Nemaha, Pawnee, Richardson	47 min
Aug 20, 4:14 AM CDT	Special Weather Statement	OAX	Butler	31 min
Aug 20, 4:36 AM CDT	Special Weather Statement	OAX	Seward	24 min
Aug 20, 4:52 AM CDT	Special Weather Statement	OAX	Seward	23 min
Aug 20, 4:54 AM CDT	Special Weather Statement	OAX	Lancaster	36 min
Aug 20, 5:17 AM CDT	Special Weather Statement	OAX	Cass	28 min
Aug 20, 6:01 AM CDT	Special Weather Statement	OAX	Saunders	44 min
Aug 20, 7:12 AM CDT	Areal Flood Warning	OAX	Seward	12 hr
Aug 20, 7:42 AM CDT	River Flood Warning	OAX	Butler	41 hr
Aug 20, 7:42 AM CDT	River Flood Warning	OAX	Seward	35 hr
Aug 20, 7:42 AM CDT	River Flood Warning	OAX	Saline	4 days
Aug 20, 7:42 AM CDT	River Flood Warning	OAX	Seward	3 days
Aug 20, 8:14 AM CDT	Special Weather Statement	OAX	Sarpy	46 min
Aug 20, 8:20 AM CDT	Severe Thunderstorm Warning	OAX	Cass, Sarpy, Saunders	25 min
Aug 20, 8:58 AM CDT	Special Weather Statement	OAX	Cass	47 min
Aug 20, 9:23 AM CDT	Special Weather Statement	OAX	Mills	22 min
Aug 20, 10:04 AM CDT	Special Weather Statement	OAX	Fremont	41 min
Aug 20, 10:46 AM CDT	Special Weather Statement	OAX	Mills	44 min
Aug 20, 11:29 AM CDT	Areal Flood Advisory	OAX	Mills	3 hr
Aug 20, 11:37 AM CDT	Special Weather Statement	OAX	Mills, Montgomery	53 min

Nearby

Severe Thunderstorm Warnings in Nebraska, 2017 Every severe thunderstorm warning 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.