Alert archive / Nebraska / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 189, NWS Omaha, NE

August 31, 2021Cass County, Otoe County, Nebraska

NWS Omaha, NE issued this severe thunderstorm warning at Aug 31, 2021, 2:14 AM CDT for Cass County, Otoe County, Nebraska. It was in force for 31 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: Aug 31, 2021, 2:14 AM CDT (07:14 UTC)
Expired: Aug 31, 2021, 2:45 AM CDT
In force: 31 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Cass County, NE, Otoe County, NE

The radar

The Omaha radar (KOAX), 56 km from the middle of the area, began a volume at 07:17 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 severe thunderstorm 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 00:00Z, 7.2 hours before the alert went out and 56 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: 1443 J/kg
Mixed-layer CIN: -31 J/kg
Mixed-layer LCL: 1305 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 4 m²/s²
0-3 km storm-relative helicity: 143 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 3.5

Open this sounding in Storm Lab

The text

As transmitted.

350 
WUUS53 KOAX 310714
SVROAX
NEC025-131-310745-
/O.NEW.KOAX.SV.W.0189.210831T0714Z-210831T0745Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Omaha/Valley Nebraska
214 AM CDT Tue Aug 31 2021

The National Weather Service in Omaha has issued a

* Severe Thunderstorm Warning for...
  North central Otoe County in southeastern Nebraska...
  Southern Cass County in southeastern Nebraska...

* Until 245 AM CDT.

* At 213 AM CDT, a severe thunderstorm was located near Weeping
  Water, or 25 miles south of Omaha, moving southeast at 35 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* This severe thunderstorm will be near...
  Avoca around 230 AM CDT.

Other locations in the path of this severe thunderstorm include
Nehawka.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4086 9633 4100 9609 4084 9591 4073 9607
      4074 9625
TIME...MOT...LOC 0713Z 316DEG 29KT 4092 9616 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Mead

1 follow-up statement

359 
WWUS53 KOAX 310737
SVSOAX

Severe Weather Statement
National Weather Service Omaha/Valley Nebraska
237 AM CDT Tue Aug 31 2021

NEC025-131-310747-
/O.EXP.KOAX.SV.W.0189.000000T0000Z-210831T0745Z/
Otoe NE-Cass NE-
237 AM CDT Tue Aug 31 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTH CENTRAL OTOE AND
SOUTHERN CASS COUNTIES WILL EXPIRE AT 245 AM CDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However gusty
winds are still possible with this thunderstorm.

LAT...LON 4086 9633 4100 9609 4084 9591 4073 9607
      4074 9625
TIME...MOT...LOC 0737Z 316DEG 29KT 4078 9599 

$$

Mead

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 30, 6:45 PM CDT, 7 hours 29 minutes earlier.

Area forecast discussion, Aug 30, 6:45 PM CDT, 7 hours 29 minutes before

Area Forecast Discussion
National Weather Service Omaha/Valley NE
645 PM CDT Mon Aug 30 2021

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 307 PM CDT Mon Aug 30 2021

Early afternoon analysis showed a warm front gradually moving
northward through area, which will likely provide a focus for
thunderstorm development this evening/tonight. Still some
questions on exact timing and location of storm initiation, but
seems like somewhere in the 7 PM to 9 PM window would be
reasonable as a low level jet strengthens, pointing into the front
in north-central Nebraska/south-central South Dakota, which will
be more or less co- located with the left exit region of an
incoming upper level jet. That said, convergence along the front
could allow for some slightly earlier development. Either way,
there will be sufficient instability and shear for a severe
weather threat, including potential supercells as storms first get
going. Initial cells are expected to congeal into an MCS with a
transition from a large hail and damaging wind threat to a
damaging wind and heavy rain/localized flooding threat. Given
expected precipitable water values around 1.75", warm cloud
depths around 3.5 km, recent rainfall, and the aforementioned low
level jet/surface boundary interaction, the ingredients seem to be
there for flooding and a potential flash flood watch. However,
guidance is persistent in the MCS being fairly progressive as it
moves through, so elected to hold off on said watch at this time.
While the aforementioned ingredients may not lead to a widespread
flooding threat, they may enhance a damaging wind threat via
downburst potential. In addition, guidance suggests 0-3 km shear
nearing 30 kts along with decent hodograph curvature in the low
levels, so can't rule out mesovortex genesis and perhaps a tornado
threat, though low level thermodynamic profiles aren't exactly
favorable.

Storms should exit the area Tuesday morning, giving way to
another "cooler" day with highs in the upper 70s to lower 80s.
However, upper level ridging will begin to build in and
southeasterly low level flow will usher moisture and warmer air,
leading to at least a slight warmup for Wednesday and Thursday.
While the warmest air looks to remain just west of the forecast
area, still expect high temperatures back in the mid to upper 80s
with a few spots making a run at 90. By Thursday night, expect
shortwave energy and an associated surface low to slide through
the Dakotas and drag a cold front through the forecast area
through Friday. With the warm, moist air in place ahead of it,
expect more shower and storm chances. The front looks to stall in
or just south of the forecast area heading into the weekend, with
daily temperatures getting back down into the upper 70s to lower
80s. Additional shortwaves are also progged to move through upper
level zonal flow and perhaps lead to more shower and storm
chances, pending exact boundary location.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 631 PM CDT Mon Aug 30 2021

Convection Allowing Models (CAMs) are in good agreement in moving
a line of storms from the South Dakota border to the southwest
through eastern Nebraska and western Iowa. Storm development is
expected near 06Z. Hail will be an early concern, but as the event
evolves strong wind gusts will be the primary concern.

CAMs suggest that a secondary line of storms will develop behind
the initial system that moves through. Generally, this line will
impact areas farther to the west and south. This secondary line
may potentially impact KLNK as late as 14Z.

After the storms move through, MVFR ceilings will be possible west
of KOMA, and may be in place between 12Z and 17Z.

&&

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

DISCUSSION...CA
AVIATION...Fajman

Hazardous weather outlook, Aug 30, 3:37 PM CDT, 10 hours 37 minutes before

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
337 PM CDT Mon Aug 30 2021

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-311200-
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-
337 PM CDT Mon Aug 30 2021

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

A few thunderstorms will be possible into early this evening,
with the highest chances in northeast Nebraska.

A line of thunderstorms is then expected to move through the area
after sunset into early Tuesday morning. Damaging winds, large
hail, and heavy rain leading to localized flooding are possible
with these storms.

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

Additional thunderstorms will be possible Thursday through the
weekend with the passage of a cold front.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated, but any severe storm or
flooding reports are appreciated.

In the hours before

Local storm report, Aug 31, 1:08 AM CDT, 1 hour 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
108 AM CDT TUE AUG 31 2021

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

0107 AM     TSTM WND GST     1 NNW FREMONT           41.45N 96.50W
08/31/2021  E70 MPH          DODGE              NE   TRAINED SPOTTER

            TRAINED SPOTTER ESTIMATED PEAK WIND GUST OF
            70 TO 80 MPH.

&&

PF

Local storm report, Aug 31, 1:12 AM CDT, 1 hour 2 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
112 AM CDT TUE AUG 31 2021

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

1230 AM     TSTM WND GST     BLAIR                   41.54N 96.14W
08/31/2021  E60 MPH          WASHINGTON         NE   STORM CHASER

            POWER ALSO OUT.

&&

Local storm report, Aug 31, 1:14 AM CDT, 1 hour before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
114 AM CDT TUE AUG 31 2021

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

1243 AM     HAIL             SNYDER                  41.70N 96.79W
08/31/2021  U1.00 INCH       DODGE              NE   PUBLIC

            REPORT FROM MPING: QUARTER (1.00 IN.).

&&

Local storm report, Aug 31, 1:33 AM CDT, 41 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
133 AM CDT TUE AUG 31 2021

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

0133 AM     TSTM WND GST     1 WNW VALLEY            41.32N 96.37W
08/31/2021  M58 MPH          DOUGLAS            NE   CO-OP OBSERVER

&&

Local storm report, Aug 31, 1:45 AM CDT, 29 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
145 AM CDT TUE AUG 31 2021

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

0135 AM     TSTM WND GST     1 WNW VALLEY            41.32N 96.37W
08/31/2021  M58 MPH          DOUGLAS            NE   CO-OP OBSERVER

            PEAK WIND GUST OF 58 MPH WAS MEASURED AT THE
            OFFICE.

&&

PF

Local storm report, Aug 31, 2:09 AM CDT, 5 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
209 AM CDT TUE AUG 31 2021

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

0145 AM     TSTM WND GST     4 N GRETNA              41.20N 96.25W
08/31/2021  E60 MPH          DOUGLAS            NE   NWS EMPLOYEE

&&

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 30, 10:29 PM CDT	Severe Thunderstorm Warning	OAX	Cedar, Knox, Pierce, Wayne	46 min
Aug 30, 10:31 PM CDT	Severe Thunderstorm Warning	OAX	Wayne	44 min
Aug 30, 10:54 PM CDT	Severe Thunderstorm Warning	OAX	Cedar	39 min
Aug 30, 11:01 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Cuming, Stanton, Wayne	44 min
Aug 30, 11:06 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Pierce, Wayne	54 min
Aug 30, 11:22 PM CDT	Special Weather Statement	OAX	Pierce	23 min
Aug 30, 11:35 PM CDT	Severe Thunderstorm Warning	OAX	Knox	40 min
Aug 30, 11:42 PM CDT	Severe Thunderstorm Warning	OAX	Cuming, Stanton, Wayne	48 min
Aug 30, 11:54 PM CDT	Severe Thunderstorm Warning	OAX	Madison, Pierce, Stanton, Wayne	24 min
Aug 31, 12:00 AM CDT	Severe Thunderstorm Warning	OAX	Colfax, Cuming, Dodge, Stanton	45 min
Aug 31, 12:04 AM CDT	Areal Flood Advisory	OAX	Cedar, Cuming, Knox, Pierce, Stanton, Thurston and 1 more	6 hr
Aug 31, 12:09 AM CDT	Severe Thunderstorm Warning	OAX	Antelope, Knox, Pierce	36 min
Aug 31, 12:15 AM CDT	Severe Thunderstorm Warning	OAX	Washington	26 min
Aug 31, 12:25 AM CDT	Areal Flood Advisory	OAX	Burt, Washington	5 hr
Aug 31, 12:31 AM CDT	Severe Thunderstorm Warning	OAX	Burt, Cuming, Dodge, Saunders, Washington	29 min
Aug 31, 12:47 AM CDT	Areal Flood Advisory	OAX	Knox	5 hr
Aug 31, 12:53 AM CDT	Severe Thunderstorm Warning	OAX	Burt, Dodge, Douglas, Saunders, Washington	37 min
Aug 31, 1:19 AM CDT	Areal Flood Advisory	OAX	Burt, Washington	4 hr
Aug 31, 1:22 AM CDT	Areal Flood Advisory	OAX	Burt, Colfax, Cuming, Dodge, Stanton, Thurston and 1 more	6 hr
Aug 31, 1:22 AM CDT	Severe Thunderstorm Warning	OAX	Dodge, Douglas, Saunders, Washington	23 min
Aug 31, 1:35 AM CDT	Severe Thunderstorm Warning	OAX	Cass, Douglas, Sarpy, Saunders	25 min
Aug 31, 1:36 AM CDT	Flash Flood Warning	OAX	Antelope, Knox, Pierce	4 hr
Aug 31, 1:46 AM CDT	Areal Flood Advisory	OAX	Dodge, Douglas, Sarpy, Washington	5 hr
Aug 31, 1:56 AM CDT	Severe Thunderstorm Warning	OAX	Cass, Lancaster, Sarpy, Saunders	34 min
Aug 31, 3:18 AM CDT	Special Weather Statement	OAX	Antelope	27 min
Aug 31, 5:02 AM CDT	Special Weather Statement	OAX	Butler	28 min
Aug 31, 5:26 AM CDT	Special Weather Statement	OAX	Butler	34 min
Aug 31, 5:35 AM CDT	Areal Flood Advisory	OAX	Butler, Cass, Colfax, Dodge, Douglas, Lancaster and 4 more	77 min
Aug 31, 5:41 AM CDT	Areal Flood Warning	OAX	Antelope, Burt, Cedar, Colfax, Cuming, Dodge and 7 more	9 hr
Aug 31, 5:56 AM CDT	Special Weather Statement	OAX	Seward	34 min
Aug 31, 6:18 AM CDT	Special Weather Statement	OAX	Cass, Lancaster, Otoe, Saline	27 min
Aug 31, 6:28 AM CDT	Severe Thunderstorm Warning	OAX	Cass, Gage, Johnson, Lancaster, Nemaha, Otoe and 1 more	47 min
Aug 31, 6:43 AM CDT	Severe Thunderstorm Warning	OAX	Gage, Jefferson, Johnson, Lancaster, Pawnee, Saline	32 min
Aug 31, 7:12 AM CDT	Severe Thunderstorm Warning	OAX	Gage, Jefferson, Johnson, Nemaha, Otoe, Pawnee and 1 more	48 min
Aug 31, 7:58 AM CDT	Severe Thunderstorm Warning	OAX	Gage, Jefferson, Johnson, Nemaha, Pawnee, Richardson	10 min

Nearby

Severe Thunderstorm Warnings in Nebraska, 2021 Every severe thunderstorm warning in 2021

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.