Alert archive / Nebraska / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 276, NWS Omaha, NE

September 18, 2018Cass County, Lancaster County, Otoe County, Nebraska

NWS Omaha, NE issued this severe thunderstorm warning at Sep 18, 2018, 4:35 PM CDT for Cass County, Lancaster County, Otoe County, Nebraska. It was in force for 40 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
Sep 18, 2018, 4:35 PM CDT (21:35 UTC)
Expired
Sep 18, 2018, 5:15 PM CDT
In force
40 min
Issued by
NWS Omaha, NE
Area
Storm-based polygon
Hail
1.75 in
Wind
60.0 mph

Counties Cass County, NE, Lancaster County, NE, Otoe County, NE

The radar

The Omaha radar (KOAX), 60 km from the middle of the area, began a volume at 21:34 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 12:00Z, 9.6 hours before the alert went out and 60 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 12:00Z on 2018-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1380 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 12:00Z on 2018-09-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -3 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
1380 J/kg
Mixed-layer CIN
-109 J/kg
Mixed-layer LCL
1445 m above ground
0-6 km bulk shear
21 kt
0-1 km storm-relative helicity
-3 m²/s²
0-3 km storm-relative helicity
-25 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 Sep 18, 3:28 PM CDT, 1 hour 7 minutes earlier.

Area forecast discussion, Sep 18, 3:28 PM CDT, 1 hour 7 minutes before
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Hazardous weather outlook, Sep 18, 11:36 AM CDT, 4 hours 59 minutes before
Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
1136 AM CDT Tue Sep 18 2018

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-190645-
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-
1136 AM CDT Tue Sep 18 2018

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

.DAY ONE...This Afternoon and Tonight

Isolated strong to severe thunderstorms are possible north of
Interstate 80. There is a marginal risk for severe storms, with
isolated one inch hail, gusty winds, and heavy downpours of rain
being the main threats.

Minor flooding will continue along the Missouri River
upstream of Lewis and Clark Lake in Knox County and in the vicinity
of Brownsville.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Isolated thunderstorms possible north of Interstate 80 Wednesday,
with more widespread thunderstorm activity for all of eastern
Nebraska and western Iowa Wednesday night and Thursday. Though the
overall risk of severe storms is low over this period, a few stronger
storms are possible.

Minor flooding will continue along the Missouri River upstream of
Lewis and Clark Lake in Knox County. Minor flooding along the
Missouri River in the vicinity of Brownsville should subside by
Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time, however local
spotters may be needed for locally strong to severe storms.

Zapotocny

In the hours before

Local storm report, Sep 18, 3:34 PM CDT, 1 hour 1 minute before
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Local storm report, Sep 18, 3:38 PM CDT, 57 minutes before
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Special weather statement, Sep 18, 4:00 PM CDT, 35 minutes before
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Special weather statement, Sep 18, 4:04 PM CDT, 31 minutes before
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Local storm report, Sep 18, 4:06 PM CDT, 29 minutes before
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Local storm report, Sep 18, 4:07 PM CDT, 28 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Sep 18, 2:29 PM CDTSpecial Weather StatementOAXDodge46 min
Sep 18, 2:54 PM CDTSevere Thunderstorm WarningOAXSaunders36 min
Sep 18, 3:22 PM CDTSevere Thunderstorm WarningOAXSaunders38 min
Sep 18, 3:55 PM CDTSevere Thunderstorm WarningOAXCass, Sarpy, Saunders35 min
Sep 18, 4:00 PM CDTSpecial Weather StatementOAXOtoe30 min
Sep 18, 4:04 PM CDTSpecial Weather StatementOAXLancaster56 min
Sep 18, 4:08 PM CDTSevere Thunderstorm WarningOAXCass, Lancaster, Sarpy, Saunders52 min
Sep 18, 4:13 PM CDTSevere Thunderstorm WarningOAXJohnson, Lancaster, Otoe32 min
Sep 18, 4:25 PM CDTSevere Thunderstorm WarningOAXCass, Sarpy50 min
Sep 18, 4:49 PM CDTSevere Thunderstorm WarningOAXCass, Otoe41 min
Sep 18, 11:28 AM CDTSpecial Weather StatementOAXMonona32 min

Nearby

Severe Thunderstorm Warnings in Nebraska, 2018Every severe thunderstorm 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.