Alert archive / Nebraska / Mesoscale Discussions in 2016

Mesoscale Discussion 1682

September 12, 20164 states

The Storm Prediction Center issued this mesoscale discussion at Sep 12, 2016, 5:31 PM CDT for 4 states. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Sep 12, 2016, 5:31 PM CDT (22:31 UTC)
Expired: Sep 12, 2016, 7:30 PM CDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 26 counties

Adams County, IA, Audubon County, IA, Cass County, IA, Fremont County, IA, Harrison County, IA, Mills County, IA, Montgomery County, IA, Page County, IA, Pottawattamie County, IA, Shelby County, IA, Marshall County, KS, Nemaha County, KS, Washington County, KS, Atchison County, MO, Cass County, NE, Douglas County, NE, Gage County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Otoe County, NE, Pawnee County, NE, Richardson County, NE, Saline County, NE, Sarpy County, NE

The radar

The Omaha radar (KOAX), 77 km from the middle of the area, began a volume at 22:34 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, 10.5 hours before the alert went out and 77 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: 106 J/kg
Mixed-layer CIN: -756 J/kg
Mixed-layer LCL: 1307 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 325 m²/s²
0-3 km storm-relative helicity: 307 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

047 
ACUS11 KWNS 122232
SWOMCD
SPC MCD 122231 
IAZ000-MOZ000-NEZ000-KSZ000-130030-

MESOSCALE DISCUSSION 1682
NWS STORM PREDICTION CENTER NORMAN OK
0531 PM CDT MON SEP 12 2016

AREAS AFFECTED...NERN KS THROUGH SERN NEB...EXTREME NWRN MO AND SWRN
IA.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 122231Z - 130030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...THUNDERSTORMS DEVELOPING FROM NERN KS THROUGH SERN NEB
INTO SWRN IA MAY POSE AT LEAST A MODEST RISK FOR A FEW INSTANCES OF
DAMAGING WIND AND HAIL THIS EVENING. AT THIS TIME OVERALL THREAT
DOES NOT APPEAR TO BE SUFFICIENT FOR A WW...BUT TRENDS WILL CONTINUE
TO BE MONITORED.

DISCUSSION...EARLY THIS EVENING A COLD FRONT EXTENDS FROM NWRN IA
THROUGH SERN NEB INTO NCNTRL KS. AN AXIS OF MODERATE INSTABILITY
WITH 1500-2000 J/KG MLCAPE RESIDES ALONG MOIST AXIS IN VICINITY OF
AND JUST AHEAD OF THIS BOUNDARY. BASED ON RAP FORECAST SOUNDINGS...A
MODEST CAPPING INVERSION REMAINS IN WARM SECTOR. HOWEVER...AN MCV IS
EVIDENT OVER NERN KS AND SERN NEB...AND THIS FEATURE WILL CONTINUE
EWD THIS EVENING. DESPITE A STABILIZING BOUNDARY LAYER...DEEPER
ASCENT ASSOCIATED WITH THE MCV AND STRENGTHENING SWLY LLJ
INTERACTING WITH THE FRONTAL ZONE MAY PROVE SUFFICIENT TO INITIATE A
FEW THUNDERSTORMS THIS EVENING. WEAK EFFECTIVE BULK SHEAR WILL
SUPPORT MULTICELL STORM MODES POSING A RISK FOR A FEW INSTANCES OF
DAMAGING WIND AND HAIL THROUGH EARLY-MID EVENING.

..DIAL/GUYER.. 09/12/2016

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

ATTN...WFO...DMX...EAX...OAX...TOP...GID...

LAT...LON   40069770 41049658 41899583 41959480 41009469 39629611
            39399733 40069770

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 12, 5:54 PM CDT	Mesoscale Discussion	SPC	Barber, Barton, Clark, Comanche, Edwards, Ellsworth and 13 more	2 hr

Nearby

Mesoscale Discussions in Nebraska, 2016 Mesoscale Discussions in Iowa, 2016 Mesoscale Discussions in Kansas, 2016 Every mesoscale discussion in 2016

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.