Alert archive / Nebraska / Mesoscale Discussions in 2012

Mesoscale Discussion 844

May 19, 2012Mills County, Pottawattamie County, Iowa; 6 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at May 19, 2012, 9:18 PM CDT for Mills County, Pottawattamie County, Iowa; 6 counties in Nebraska. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: May 19, 2012, 9:18 PM CDT (02:18 UTC)
Expired: May 19, 2012, 10:15 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center

Counties Mills County, IA, Pottawattamie County, IA, Cass County, NE, Douglas County, NE, Johnson County, NE, Lancaster County, NE, Otoe County, NE, Sarpy County, NE

The radar

The Omaha radar (KOAX), 47 km from the middle of the area, began a volume at 02:18 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 00:00Z, 2.3 hours before the alert went out and 47 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: 1597 J/kg
Mixed-layer CIN: -7 J/kg
Mixed-layer LCL: 1383 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 122 m²/s²
0-3 km storm-relative helicity: 188 m²/s²
Significant tornado parameter: 0.8
Supercell composite: 8.3

Open this sounding in Storm Lab

The text

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

816 
ACUS11 KWNS 200219
SWOMCD
SPC MCD 200218
IAZ000-NEZ000-200315-

MESOSCALE DISCUSSION 0844
NWS STORM PREDICTION CENTER NORMAN OK
0918 PM CDT SAT MAY 19 2012

AREAS AFFECTED...SERN NEB...SWRN IA

CONCERNING...SEVERE THUNDERSTORM WATCH 281...

VALID 200218Z - 200315Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 281
CONTINUES.

SUMMARY...WW 281 SHOULD LARGELY BE ALLOWED TO EXPIRE AS SCHEDULED AT
03Z...BUT A LOCAL TEMPORAL EXTENSION MAY BE CONSIDERED FOR WFO OAX.

DISCUSSION...SRN PORTION OF LEAD MCS CLUSTER HAS WEAKENED IN WRN IA
AS IT SHIFTED AWAY FROM THE INSTABILITY AXIS...PRESENT W OF THE MO
RIVER. A SMALLER CLUSTER OF STRONG CONVECTION REMAINS IN THE WAKE OF
THE TRAILING COMPOSITE OUTFLOW/COLD FRONT. ALTHOUGH THIS ACTIVITY
SHOULD LARGELY REMAIN ALONG/N OF THE BOUNDARY...THE PRESENCE OF THIS
BOUNDARY MAY BE SUFFICIENT TO MAINTAIN A HAIL/LOCALIZED DAMAGING
WIND RISK FOR THE NEXT COUPLE OF HOURS. STILL...WITH SURFACE DEW
POINTS FALLING IN THE WARM SECTOR ALONG THE MO RIVER AND A RATHER
DRY BOUNDARY LAYER SAMPLED IN THE 00Z TOP RAOB...THIS SECOND
CONVECTIVE WAVE MAY STRUGGLE TO INTENSIFY.

..GRAMS.. 05/20/2012

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

ATTN...WFO...OAX...

LAT...LON   41699536 41549516 41179529 40589590 40319621 40269645
            40459669 40899672 41129658 41439604 41699536

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 19, 8:11 PM CDT	Mesoscale Discussion	SPC	Audubon, Buena Vista, Calhoun, Carroll, Cass, Cherokee and 13 more	64 min
May 19, 10:33 PM CDT	Mesoscale Discussion	SPC	Audubon, Buena Vista, Calhoun, Carroll, Cass, Cherokee and 20 more	57 min

Nearby

Mesoscale Discussions in Nebraska, 2012 Mesoscale Discussions in Iowa, 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.