Alert archive / Nebraska / Tornado Watches in 2012
Tornado Watch 251
The Storm Prediction Center issued this tornado watch at May 5, 2012, 5:31 PM CDT for Plymouth County, Sioux County, Woodbury County, Iowa; 21 counties in Nebraska; 4 counties in South Dakota. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- May 5, 2012, 5:31 PM CDT (22:31 UTC)
- Expired
- May 5, 2012, 10:05 PM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 3 in
- Strongest gust expected
- 60 kt
All 28 counties
Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Antelope County, NE, Boone County, NE, Cedar County, NE, Custer County, NE, Dakota County, NE, Dawson County, NE, Dixon County, NE, Frontier County, NE, Garfield County, NE, Greeley County, NE, Holt County, NE, Knox County, NE, Lincoln County, NE, Loup County, NE, Madison County, NE, Pierce County, NE, Sherman County, NE, Thurston County, NE, Valley County, NE, Wayne County, NE, Wheeler County, NE, Bon Homme County, SD, Clay County, SD, Union County, SD, Yankton County, SD
The radar
The North Platte radar (KLNX), 150 km from the middle of the area, began a volume at 22:31 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 50%
- One or more EF2 to EF5 tornadoes
- 30%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 50%
- One or more hailstones of 2 inches or more
- 60%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 5, 9:20 PM CDT | Severe Thunderstorm Warning | LBF | Lincoln, Logan, McPherson | 40 min |
| May 5, 9:20 PM CDT | Severe Thunderstorm Warning | LBF | Brown, Holt, Rock | 40 min |
| May 5, 9:36 PM CDT | Severe Thunderstorm Warning | LBF | Boyd, Holt, Keya Paha, Rock | 39 min |
| May 5, 9:55 PM CDT | Severe Thunderstorm Warning | LBF | Brown, Holt, Rock | 35 min |
| May 5, 10:00 PM CDT | Severe Thunderstorm Warning | LBF | Lincoln, Logan, McPherson | 45 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 10.5 hours before the alert went out and 178 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.
- Mixed-layer CAPE
- 4 J/kg
- Mixed-layer CIN
- -810 J/kg
- Mixed-layer LCL
- 2042 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 190 m²/s²
- 0-3 km storm-relative helicity
- 202 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
840
WWUS20 KWNS 052235
SEL1
SPC WW 052235
IAZ000-NEZ000-SDZ000-060400-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 251
NWS STORM PREDICTION CENTER NORMAN OK
535 PM CDT SAT MAY 5 2012
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
EXTREME NORTHWEST IOWA
CENTRAL AND NORTHEAST NEBRASKA
EXTREME SOUTHEAST SOUTH DAKOTA
EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 535 PM UNTIL
1100 PM CDT.
TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 35 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 50 MILES WEST SOUTHWEST OF
BROKEN BOW NEBRASKA TO 35 MILES NORTH NORTHEAST OF SIOUX CITY
IOWA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.
OTHER WATCH INFORMATION...CONTINUE...WW 248...WW 249...WW 250...
DISCUSSION...STRONG SURFACE HEATING/DEEP MIXING IN THE WARM SECTOR
HAS REDUCED CONVECTIVE INHIBITION ACROSS NEB...AND VISIBLE IMAGERY
IS BEGINNING TO SHOW DEEPENING CUMULUS ALONG THE SURFACE FRONT FROM
SE OF LBF TO SW OF YKN. THE SITUATION IS COMPLICATED BY LOWER
DEWPOINTS IN THE WARM SECTOR AND A QUICK TRANSITION TO STRONGER
SHEAR/COOLER TEMPERATURES ACROSS THE FRONT...LEAVING ONLY A NARROW
CORRIDOR WITH SURFACE-BASED SUPERCELL/TORNADO POTENTIAL.
STILL...THE ORIENTATION OF THE FRONT APPEARS TO BE ROUGHLY PARALLEL
TO EXPECTED STORM MOTION...SO ANY STORMS THAT FORM ALONG THE
IMMEDIATE SURFACE FRONT COULD REMAIN IN THE NARROW FAVORABLE
CORRIDOR LONG ENOUGH TO BE A TORNADO THREAT. IN ADDITION TO THE
TORNADO RISK...VERY LARGE HAIL WILL BE POSSIBLE WITH ANY SUSTAINED
STORMS THROUGH LATE EVENING.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
550. MEAN STORM MOTION VECTOR 24025.
...THOMPSONSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 8:30 PM CDT | Mesoscale Discussion | SPC | Allamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 10 more | 60 min |
| May 4, 9:54 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Cherokee, Crawford, Harrison, Ida, Monona and 5 more | 96 min |
| May 5, 6:49 AM CDT | Severe Thunderstorm Watch | SPC | Cherokee, Lyon, O'Brien, Osceola, Plymouth, Sioux | 7 hr |
| May 5, 11:38 AM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Cerro Gordo, Chickasaw, Clayton, Emmet, Fayette and 8 more | 6 hr |
| May 5, 2:09 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more | 96 min |
| May 5, 2:58 PM CDT | Mesoscale Discussion | SPC | Allamakee, Dickinson, Emmet, Howard, Kossuth, Mitchell and 3 more | 62 min |
| May 5, 3:52 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more | 83 min |
| May 5, 4:56 PM CDT | Mesoscale Discussion | SPC | Bremer, Buchanan, Clayton, Delaware, Dubuque, Fayette and 1 more | 94 min |
| May 5, 6:46 PM CDT | Severe Thunderstorm Watch | SPC | Lyon | 6 hr |
| May 4, 10:55 PM CDT | Mesoscale Discussion | SPC | Adams, Antelope, Boone, Buffalo, Burt, Butler and 34 more | 35 min |
| May 4, 11:00 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Boone, Buffalo, Burt, Butler, Cass and 34 more | 3 hr |
| May 5, 6:21 PM CDT | Mesoscale Discussion | SPC | Boyd, Brown, Keya Paha, Rock, Thomas | 84 min |
| May 5, 6:44 PM CDT | Mesoscale Discussion | SPC | Banner, Cheyenne, Kimball | 61 min |
| May 5, 3:06 AM CDT | Mesoscale Discussion | SPC | Custer, Fall River, Haakon, Hughes, Hyde, Jackson and 9 more | 84 min |
| May 5, 3:19 AM CDT | Severe Thunderstorm Watch | SPC | Bennett, Buffalo, Butte, Custer, Dewey, Fall River and 17 more | 9 hr |
| May 5, 9:50 AM CDT | Mesoscale Discussion | SPC | Aurora, Beadle, Brookings, Brule, Buffalo, Davison and 13 more | 55 min |
Nearby
Tornado Watches in Nebraska, 2012Tornado Watches in South Dakota, 2012Tornado Watches in Iowa, 2012Every tornado watch in 2012
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.