Alert archive / Nebraska / Mesoscale Discussions in 2012

Mesoscale Discussion 548

April 15, 20129 counties in Nebraska; Clay County, South Dakota

The Storm Prediction Center issued this mesoscale discussion at Apr 15, 2012, 1:18 PM CDT for 9 counties in Nebraska; Clay County, South Dakota. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Apr 15, 2012, 1:18 PM CDT (18:18 UTC)
Expired: Apr 15, 2012, 2:45 PM CDT
In force: 87 min
Issued by: the Storm Prediction Center

Counties Antelope County, NE, Cedar County, NE, Garfield County, NE, Greeley County, NE, Knox County, NE, Pierce County, NE, Sherman County, NE, Valley County, NE, Wheeler County, NE, Clay County, SD

The radar

The Omaha radar (KOAX), 168 km from the middle of the area, began a volume at 18:21 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, 6.3 hours before the alert went out and 168 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: 308 J/kg
Mixed-layer CIN: -118 J/kg
Mixed-layer LCL: 599 m above ground
0-6 km bulk shear: 92 kt
0-1 km storm-relative helicity: 262 m²/s²
0-3 km storm-relative helicity: 342 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.7

Open this sounding in Storm Lab

The text

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

387 
ACUS11 KWNS 151818
SWOMCD
SPC MCD 151818 
SDZ000-NEZ000-151945-

MESOSCALE DISCUSSION 0548
NWS STORM PREDICTION CENTER NORMAN OK
0118 PM CDT SUN APR 15 2012

AREAS AFFECTED...PORTIONS OF CNTRL/NERN NEB AND FAR SERN SD

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 151818Z - 151945Z

A FEW STORMS COULD INTENSIFY THIS AFTERNOON AND PRODUCE SMALL
HAIL...GUSTY WINDS...FUNNEL CLOUDS...AND PERHAPS A BRIEF/WEAK
TORNADO. WHILE TRENDS WILL CONTINUE TO BE MONITORED...THE
ANTICIPATED VERY MARGINAL/ISOLATED THREAT FOR ANY SVR STORMS WILL
LIKELY PRECLUDE THE NEED FOR A WW.

EARLY-AFTERNOON SFC MESOANALYSIS DEPICTS AN OCCLUDED FRONT EXTENDING
FROM A SFC LOW 30 MILES ESE OF BROKEN BOW NEB TO 35 MILES NNW OF
SIOUX CITY IA. NEAR AND NORTHWEST OF THE OCCLUDED FRONT...MODESTLY
RICHER LOW-LEVEL MOISTURE -- SFC DEWPOINTS IN THE LOWER 50S -- IS
PRESENT COMPARED TO LOCATIONS FARTHER TO THE SE/S WHERE DEEPER
MIXING INTO DRIER AIR ALOFT IS SUPPORTING SFC DEWPOINTS IN THE UPPER
30S TO THE 40S. THE OCCLUDED FRONT WILL HAVE A TENDENCY OF MIXING
NWWD INTO THE AFTERNOON WHILE THE CNTRL NEB SFC LOW MOVES NNEWD
TOWARD A REGION OF ENHANCED SFC PRESSURE FALLS. VISIBLE SATELLITE
IMAGERY DEPICTS A WELL-DEFINED CLOUD LINE ALIGNING WITH THE OCCLUDED
FRONT...WHICH WILL REMAIN A SOURCE OF STRONG LOW-LEVEL VERTICAL
VORTICITY AND CONVERGENCE. THE AFOREMENTIONED DEWPOINTS NEAR AND
JUST NORTHWEST OF THE BOUNDARY...BENEATH A MID-LEVEL VORT MAX/COLD
CORE...MAY SUPPORT SUFFICIENT BUOYANCY FOR A FEW STRONG STORMS.
SMALL HAIL AND GUSTY WINDS WILL BE POSSIBLE. ALSO...THE
JUXTAPOSITION OF STRONG LOW-LEVEL VORTICITY AND MODEST LOW-LEVEL
BUOYANCY /I.E. 0-3-KM MLCAPE VALUES REACHING OVER 100 J PER KG IN
SOME AREAS/ ALONG THE BOUNDARY WOULD PROMOTE STRETCHING OF VERTICAL
VORTICITY...AUGMENTED BY CONVECTIVE UPDRAFTS. AS SUCH...THE THREAT
FOR A FEW FUNNEL CLOUDS AND PERHAPS A BRIEF/WEAK TORNADO MAY EXIST.

..COHEN.. 04/15/2012

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

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

LAT...LON   41459847 41089868 41019917 41529960 42079909 42569830
            42979700 42709662 42429711 42109780 41459847

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 14, 7:51 PM CDT	Mesoscale Discussion	SPC	Boyd, Burt, Cedar, Cuming, Dakota, Dixon and 6 more	84 min
Apr 14, 10:09 PM CDT	Severe Thunderstorm Watch	SPC	Antelope, Boone, Burt, Butler, Cass, Cedar and 16 more	6 hr
Apr 15, 3:25 AM CDT	Mesoscale Discussion	SPC	Adams, Burt, Butler, Cass, Clay, Colfax and 22 more	95 min
Apr 15, 12:25 PM CDT	Mesoscale Discussion	SPC	Brookings, Clark, Codington, Davison, Deuel, Grant and 10 more	65 min

Nearby

Mesoscale Discussions in Nebraska, 2012 Mesoscale Discussions in South Dakota, 2012 Every 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.