Alert archive / Nebraska / Mesoscale Discussions in 2012

Mesoscale Discussion 706

May 4, 201211 counties in Iowa; 48 counties in Nebraska; Union County, South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 4, 2012, 9:54 PM CDT for 11 counties in Iowa; 48 counties in Nebraska; Union County, South Dakota. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued
May 4, 2012, 9:54 PM CDT (02:54 UTC)
Expired
May 4, 2012, 11:30 PM CDT
In force
96 min
Issued by
the Storm Prediction Center
All 60 counties

Buena Vista County, IA, Cherokee County, IA, Crawford County, IA, Harrison County, IA, Ida County, IA, Monona County, IA, O'Brien County, IA, Plymouth County, IA, Sac County, IA, Sioux County, IA, Woodbury County, IA, Adams County, NE, Antelope County, NE, Boone 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, Garfield County, NE, Gosper County, NE, Greeley County, NE, Hall County, NE, Hamilton County, NE, Howard County, NE, Kearney County, NE, Lancaster County, NE, Loup County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Otoe County, NE, Phelps County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Rock County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Sherman County, NE, Stanton County, NE, Thurston County, NE, Valley County, NE, Washington County, NE, Wayne County, NE, Wheeler County, NE, York County, NE, Union County, SD

The radar

The Omaha radar (KOAX), 126 km from the middle of the area, began a volume at 02:55 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.9 hours before the alert went out and 125 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 00:00Z on 2012-05-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2635 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 00:00Z on 2012-05-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 71 square meters per square second.1939Sfc1 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
2635 J/kg
Mixed-layer CIN
-14 J/kg
Mixed-layer LCL
1505 m above ground
0-6 km bulk shear
38 kt
0-1 km storm-relative helicity
71 m²/s²
0-3 km storm-relative helicity
173 m²/s²
Significant tornado parameter
0.6
Supercell composite
8.5

Open this sounding in Storm Lab

The text

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

615 
ACUS11 KWNS 050254
SWOMCD
SPC MCD 050254 
IAZ000-NEZ000-SDZ000-050430-

MESOSCALE DISCUSSION 0706
NWS STORM PREDICTION CENTER NORMAN OK
0954 PM CDT FRI MAY 04 2012

AREAS AFFECTED...PARTS OF CENTRAL AND ERN NEB

CONCERNING...SEVERE THUNDERSTORM WATCH 241...

VALID 050254Z - 050430Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 241
CONTINUES.

SUMMARY...THE SVR WEATHER THREAT THROUGH THE REST OF THE EVENING IS
EXPECTED TO BE CONFINED TO CENTRAL NEB AND POTENTIALLY INTO PARTS OF
NERN AND EAST CENTRAL NEB TO THE W OF THE NEB/IA BORDER.  HAIL AND
STRONG WIND GUSTS WILL REMAIN THE PRIMARY THREATS.

FARTHER E ALONG AND E OF THE NEB/IA BORDER...A CONVECTIVELY
STABILIZED AIR MASS SUGGESTS THE ERN EXTENT OF WW 241 COULD BE
CANCELLED EARLY.  THE REST OF WW 241 SHOULD BE MAINTAINED THROUGH
05Z AND THE WRN EXTENT OF WW 239 IN CENTRAL NEB HAS BEEN TEMPORALLY
EXTENDED UNTIL 04Z.

DISCUSSION...SURFACE ANALYSIS AND TRENDS IN REGIONAL RADAR IMAGERY
SHOWED THE TRAILING OUTFLOW BOUNDARY ATTENDANT TO THE MCS THAT MOVED
EWD ACROSS NRN-NERN IA AND ADJACENT SRN-SERN MN EXTENDED FROM
CENTRAL IA /30 N DSM/ SWWD TO 25 SSE OLU...THEN WWD TO JUST S OF
LBF...AND NWWD TO WEST CENTRAL NEB.  STREAMLINE ANALYSES OF 850 MB
FLOW PER WIND PROFILERS AND WSR-88D VWP DATA INDICATED A SLY LLJ
EXTENDING FROM CENTRAL KS INTO SOUTH CENTRAL NEB WHICH SHOULD
SUSTAIN ONGOING CENTRAL NEB CONVECTIVE COMPLEX LOCATED JUST N OF THE
E-W OUTFLOW BOUNDARY.  THE LLJ INTO THIS REGION WILL PROMOTE
ISENTROPIC ASCENT AND STRENGTHENING WAA ACROSS THE ACTIVE PORTION OF
WW 241/239...WITH ELEVATED CONVECTION EXTENDING EVEN INTO NERN NEB
AND NWRN IA.  RESIDUAL MODERATE INSTABILITY ACROSS THIS REGION
COMBINED WITH EFFECTIVE BULK SHEAR OF 40-50 KT AND STEEP MIDLEVEL
LAPSE RATES WILL CONTINUE TO SUPPORT A THREAT FOR HAIL AND STRONG
WIND GUSTS WITH THE SUSTAINED UPDRAFTS.

MEANWHILE...THE SAME 850 MB STREAMLINE ANALYSIS INDICATED DIFFLUENT
FLOW OVER NERN KS WHICH SHOULD CONTINUE TO LIMIT LOW LEVEL
CONVERGENCE AND ANY NEW CONVECTIVE DEVELOPMENT IN THE SHORT TERM
INTO SERN NEB AND FAR SWRN IA.

..PETERS.. 05/05/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...DMX...FSD...OAX...GID...LBF...

LAT...LON   41420027 42359968 42509907 42409838 42649740 43229625
            43099527 42829485 41859531 40659601 40609625 40349719
            40219888 40319968 40540019 41420027

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 4, 8:30 PM CDTMesoscale DiscussionSPCAllamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 10 more60 min
May 5, 6:49 AM CDTSevere Thunderstorm WatchSPCCherokee, Lyon, O'Brien, Osceola, Plymouth, Sioux7 hr
May 5, 11:38 AM CDTSevere Thunderstorm WatchSPCAllamakee, Cerro Gordo, Chickasaw, Clayton, Emmet, Fayette and 8 more6 hr
May 5, 2:09 PM CDTMesoscale DiscussionSPCBuena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more96 min
May 5, 2:58 PM CDTMesoscale DiscussionSPCAllamakee, Dickinson, Emmet, Howard, Kossuth, Mitchell and 3 more62 min
May 5, 3:52 PM CDTMesoscale DiscussionSPCBuena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more83 min
May 5, 4:56 PM CDTMesoscale DiscussionSPCBremer, Buchanan, Clayton, Delaware, Dubuque, Fayette and 1 more94 min
May 5, 5:31 PM CDTTornado WatchSPCPlymouth, Sioux, Woodbury5 hr
May 5, 6:46 PM CDTSevere Thunderstorm WatchSPCLyon6 hr
May 4, 10:55 PM CDTMesoscale DiscussionSPCAdams, Antelope, Boone, Buffalo, Burt, Butler and 34 more35 min
May 4, 11:00 PM CDTSevere Thunderstorm WatchSPCAdams, Boone, Buffalo, Burt, Butler, Cass and 34 more3 hr
May 5, 6:21 PM CDTMesoscale DiscussionSPCBoyd, Brown, Keya Paha, Rock, Thomas84 min
May 5, 6:44 PM CDTMesoscale DiscussionSPCBanner, Cheyenne, Kimball61 min
May 5, 3:06 AM CDTMesoscale DiscussionSPCCuster, Fall River, Haakon, Hughes, Hyde, Jackson and 9 more84 min
May 5, 3:19 AM CDTSevere Thunderstorm WatchSPCBennett, Buffalo, Butte, Custer, Dewey, Fall River and 17 more9 hr
May 5, 9:50 AM CDTMesoscale DiscussionSPCAurora, Beadle, Brookings, Brule, Buffalo, Davison and 13 more55 min

Nearby

Mesoscale Discussions in Nebraska, 2012Mesoscale Discussions in Iowa, 2012Mesoscale Discussions in South Dakota, 2012Every mesoscale discussion 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.