Alert archive / Nebraska / Mesoscale Discussions in 2013

Mesoscale Discussion 1821

August 31, 20134 counties in Kansas; 32 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2013, 9:03 PM CDT for 4 counties in Kansas; 32 counties in Nebraska. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Aug 31, 2013, 9:03 PM CDT (02:03 UTC)
Expired: Aug 31, 2013, 10:00 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 36 counties

Cheyenne County, KS, Decatur County, KS, Norton County, KS, Rawlins County, KS, Adams County, NE, Antelope County, NE, Boone County, NE, Buffalo County, NE, Clay County, NE, Custer County, NE, Dawson County, NE, Dundy County, NE, Franklin County, NE, Frontier County, NE, Furnas County, NE, Garfield County, NE, Gosper County, NE, Greeley County, NE, Hall County, NE, Hamilton County, NE, Harlan County, NE, Hayes County, NE, Hitchcock County, NE, Holt County, NE, Howard County, NE, Kearney County, NE, Lincoln County, NE, Loup County, NE, Merrick County, NE, Nance County, NE, Phelps County, NE, Red Willow County, NE, Sherman County, NE, Valley County, NE, Webster County, NE, Wheeler County, NE

The radar

The Grand Island radar (KUEX), 131 km from the middle of the area, began a volume at 02:05 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

N. Platte/Lee Bi, NE (KLBF), launched 00:00Z, 2.1 hours before the alert went out and 74 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: 1826 J/kg
Mixed-layer CIN: -55 J/kg
Mixed-layer LCL: 2329 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 33 m²/s²
0-3 km storm-relative helicity: 111 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 4.3

Open this sounding in Storm Lab

The text

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

825 
ACUS11 KWNS 010203
SWOMCD
SPC MCD 010203 
NEZ000-KSZ000-COZ000-010300-

MESOSCALE DISCUSSION 1821
NWS STORM PREDICTION CENTER NORMAN OK
0903 PM CDT SAT AUG 31 2013

AREAS AFFECTED...CNTRL NEB...NW KS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 010203Z - 010300Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...AN ISOLATED SEVERE THREAT MAY DEVELOP ACROSS SCNTRL NEB
OVER THE NEXT FEW HOURS. AS UPDRAFTS INCREASE IN INTENSITY...THE
STRONGER CELLS COULD BE ACCOMPANIED BY STRONG GUSTY WINDS AND HAIL.
WW ISSUANCE CAN NOT BE RULED OUT ACROSS THE REGION LATE THIS
EVENING.

DISCUSSION...SEVERAL THUNDERSTORMS ARE DEVELOPING NEAR NORTH PLATTE
NEB ON A SHARPLY DEFINED COLD FRONT ADVANCING SEWD ACROSS THE CNTRL
PLAINS. AHEAD OF THE FRONT...MODERATE INSTABILITY IS ANALYZED WITH
MLCAPE ESTIMATED IN THE 2000 TO 2500 J/KG RANGE. IN ADDITION...THE
THEDFORD NEB WSR-88D VWP SHOWS 0-6 KM SHEAR OF ABOUT 40 KT. THIS
COMBINATION OF INSTABILITY AND SHEAR SHOULD BE SUPPORTIVE OF A
SEVERE THREAT AS CELLS INCREASE IN COVERAGE LATE THIS EVENING. AS
THE STORMS MOVE SEWD INTO A CORRIDOR OF STEEP LOW-LEVEL LAPSE
RATES...WIND DAMAGE WILL BE POSSIBLE. THE INSTABILITY MAY BE ENOUGH
FOR HAIL ESPECIALLY AS THE CELLS MOVE SEWD INTO THE STRONGER
INSTABILITY. THE SEVERE THREAT IS EXPECTED TO REMAIN ISOLATED DUE TO
A COOLING BOUNDARY LAYER LATE THIS EVENING INTO THE OVERNIGHT
PERIOD. THE COLD FRONT MAY ALSO TEND TO UNDERCUT THE STORMS AS WELL.

..BROYLES/CORFIDI.. 09/01/2013

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

ATTN...WFO...OAX...GID...LBF...GLD...

LAT...LON   42589910 41670015 41100086 40370168 39970205 39410182
            39550070 39829974 40079836 40779765 41759749 42619812
            42589910

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 31, 9:47 PM CDT	Severe Thunderstorm Watch	SPC	Dakota, Dixon	6 hr
Sep 1, 1:10 AM CDT	Mesoscale Discussion	SPC	Burt, Butler, Cass, Cedar, Colfax, Cuming and 19 more	95 min

Nearby

Mesoscale Discussions in Nebraska, 2013 Mesoscale Discussions in Kansas, 2013 Every mesoscale discussion in 2013

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.