Alert archive / Nebraska / Tornado Watches in 2007

Tornado Watch 240

May 5, 20074 states

The Storm Prediction Center issued this tornado watch at May 5, 2007, 9:31 PM CDT for 4 states. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: May 5, 2007, 9:31 PM CDT (02:31 UTC)
Expired: May 6, 2007, 4:00 AM CDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 113 counties

Cherokee County, IA, Fremont County, IA, Harrison County, IA, Ida County, IA, Lyon County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, O'Brien County, IA, Osceola County, IA, Page County, IA, Plymouth County, IA, Pottawattamie County, IA, Shelby County, IA, Sioux County, IA, Woodbury County, IA, Lincoln County, MN, Lyon County, MN, Murray County, MN, Nobles County, MN, Pipestone County, MN, Rock County, MN, Adams County, NE, Antelope County, NE, Blaine County, NE, Boone County, NE, Boyd County, NE, Brown County, NE, Buffalo County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Cedar County, NE, Clay County, NE, Colfax County, NE, Cuming County, NE, Custer County, NE, Dakota County, NE, Dawson County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Fillmore County, NE, Franklin County, NE, Furnas County, NE, Gage County, NE, Garfield County, NE, Gosper County, NE, Greeley County, NE, Hall County, NE, Hamilton County, NE, Harlan County, NE, Holt County, NE, Howard County, NE, Jefferson County, NE, Johnson County, NE, Kearney County, NE, Keya Paha County, NE, Knox County, NE, Lancaster County, NE, Loup County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Nemaha County, NE, Nuckolls County, NE, Otoe County, NE, Pawnee County, NE, Phelps County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Richardson County, NE, Rock County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Sherman County, NE, Stanton County, NE, Thayer County, NE, Thurston County, NE, Valley County, NE, Washington County, NE, Wayne County, NE, Webster County, NE, Wheeler County, NE, York County, NE, Aurora County, SD, Beadle County, SD, Bon Homme County, SD, Brookings County, SD, Brule County, SD, Charles Mix County, SD, Clay County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, Kingsbury County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Sanborn County, SD, Tripp County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 166 km from the middle of the area, began a volume at 02:33 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: 20%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 20%
Ten or more severe hail reports: 40%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

38 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
May 5, 9:42 PM CDT	Severe Thunderstorm Warning	OAX	Boone	33 min
May 5, 9:51 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Washington	24 min
May 5, 9:58 PM CDT	Flash Flood Warning	OAX	Monona	2 hr
May 5, 10:05 PM CDT	Severe Thunderstorm Warning	OAX	Pottawattamie	40 min
May 5, 10:10 PM CDT	Severe Thunderstorm Warning	FSD	Cherokee	35 min
May 5, 10:11 PM CDT	Severe Thunderstorm Warning	OAX	Otoe	34 min
May 5, 10:16 PM CDT	Severe Thunderstorm Warning	GID	Thayer	59 min
May 5, 10:21 PM CDT	Severe Thunderstorm Warning	OAX	Shelby	24 min
May 5, 10:29 PM CDT	Severe Thunderstorm Warning	FSD	O'Brien	31 min
May 5, 10:35 PM CDT	Severe Thunderstorm Warning	UNR	Tripp	55 min
May 5, 10:45 PM CDT	Severe Thunderstorm Warning	GID	Fillmore	51 min
May 5, 10:49 PM CDT	Severe Thunderstorm Warning	OAX	Nemaha, Otoe	41 min
May 5, 10:53 PM CDT	Severe Thunderstorm Warning	OAX	Pawnee	37 min
May 5, 10:54 PM CDT	Severe Thunderstorm Warning	OAX	Mills	36 min
May 5, 11:06 PM CDT	Flash Flood Warning	FSD	Cherokee, Ida, Plymouth, Woodbury	6 hr
May 5, 11:15 PM CDT	Flash Flood Warning	OAX	Pottawattamie	2 hr
May 5, 11:17 PM CDT	Severe Thunderstorm Warning	OAX	Fremont	28 min
May 5, 11:22 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Sarpy	23 min
May 5, 11:24 PM CDT	Severe Thunderstorm Warning	OAX	Otoe	36 min
May 5, 11:28 PM CDT	Severe Thunderstorm Warning	FSD	Bon Homme, Yankton	32 min
May 5, 11:34 PM CDT	Flash Flood Warning	OAX	Harrison, Monona	116 min
May 5, 11:34 PM CDT	Severe Thunderstorm Warning	OAX	Knox	41 min
May 5, 11:44 PM CDT	Severe Thunderstorm Warning	OAX	Pawnee	46 min
May 5, 11:49 PM CDT	Tornado Warning	OAX	Pottawattamie	41 min
May 5, 11:53 PM CDT	Severe Thunderstorm Warning	FSD	Bon Homme, Yankton	37 min
May 6, 12:19 AM CDT	Severe Thunderstorm Warning	OAX	Dodge	41 min
May 6, 12:22 AM CDT	Flash Flood Warning	FSD	Buena Vista, Clay, O'Brien	6 hr
May 6, 12:32 AM CDT	Flash Flood Warning	OAX	Gage, Johnson, Otoe, Pawnee	118 min
May 6, 12:56 AM CDT	Flash Flood Warning	OAX	Pottawattamie	2 hr
May 6, 12:56 AM CDT	Flash Flood Warning	OAX	Pottawattamie	2 hr
May 6, 1:01 AM CDT	Severe Thunderstorm Warning	OAX	Gage, Jefferson	59 min
May 6, 1:06 AM CDT	Flash Flood Warning	OAX	Cass, Sarpy	114 min
May 6, 1:14 AM CDT	Flash Flood Warning	OAX	Jefferson	2 hr
May 6, 1:23 AM CDT	Flash Flood Warning	OAX	Harrison, Monona	37 min
May 6, 1:28 AM CDT	Flash Flood Warning	OAX	Harrison, Monona	2 hr
May 6, 1:51 AM CDT	Severe Thunderstorm Warning	OAX	Page	24 min
May 6, 2:21 AM CDT	Severe Thunderstorm Warning	OAX	Montgomery	24 min
May 6, 2:25 AM CDT	Flash Flood Warning	OAX	Fremont, Mills, Montgomery, Page	2 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.5 hours before the alert went out and 226 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: 2431 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 1133 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 22 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 7.3

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000
WWUS20 KWNS 060231
SEL0  
SPC WW 060231
IAZ000-MNZ000-NEZ000-SDZ000-060900-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 240
NWS STORM PREDICTION CENTER NORMAN OK
930 PM CDT SAT MAY 5 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF 

       WESTERN IOWA
       SOUTHWEST MINNESOTA
       CENTRAL AND EASTERN NEBRASKA
       SOUTHERN AND EASTERN SOUTH DAKOTA

EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 930 PM
UNTIL 400 AM CDT.

TORNADOES...HAIL TO 1.5 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 110 STATUTE
MILES EAST AND WEST OF A LINE FROM 10 MILES NORTHEAST OF HURON
SOUTH DAKOTA TO 55 MILES SOUTHEAST OF HASTINGS NEBRASKA.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU0).

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...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 232...TORNADO WATCH NUMBER 235. WATCH NUMBER 232 235
WILL NOT BE IN EFFECT AFTER 930 PM CDT. CONTINUE...WW 234...WW
236...WW 237...WW 238...WW 239...

DISCUSSION...SCATTERED STORMS/SUPERCELLS EXPECTED TO MOVE/DEVELOP
NNE ACROSS WW AREA...BOTH ALONG NOSE OF CONFLUENT LLJ AND INVOF DRY
LINE/LEE TROUGH IN WRN PART OF WW.  DESPITE WEAKENING SFC-BASED
INSTABILITY... ENVIRONMENT MAY SUPPORT ADDITIONAL TORNADOES AS WELL
AS HAIL/HIGH WIND.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 21045.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 5, 7:22 PM CDT	Tornado Watch	SPC	Adair, Adams, Audubon, Boone, Buena Vista, Calhoun and 21 more	9 hr
May 5, 7:26 PM CDT	Mesoscale Discussion	SPC	Lyon, Plymouth, Sioux, Woodbury	94 min
May 5, 9:16 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Boone, Buena Vista, Calhoun and 21 more	59 min
May 6, 1:50 AM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Boone, Buena Vista, Calhoun and 37 more	85 min
May 6, 4:08 AM CDT	Mesoscale Discussion	SPC	Appanoose, Clarke, Davis, Decatur, Lucas, Madison and 7 more	2 hr
May 6, 4:40 AM CDT	Severe Thunderstorm Watch	SPC	Appanoose, Clarke, Dallas, Davis, Decatur, Jasper and 10 more	4 hr
May 6, 7:10 AM CDT	Mesoscale Discussion	SPC	Appanoose, Davis, Grundy, Mahaska, Marshall, Monroe and 3 more	95 min
May 5, 11:24 PM CDT	Mesoscale Discussion	SPC	Furnas	66 min

Nearby

Tornado Watches in Nebraska, 2007 Tornado Watches in South Dakota, 2007 Tornado Watches in Iowa, 2007 Every tornado watch in 2007

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.