Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 1663

July 31, 201222 counties in Illinois; 9 counties in Indiana

The Storm Prediction Center issued this mesoscale discussion at Jul 31, 2012, 12:11 PM CDT for 22 counties in Illinois; 9 counties in Indiana. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued: Jul 31, 2012, 12:11 PM CDT (17:11 UTC)
Expired: Jul 31, 2012, 1:15 PM CDT
In force: 64 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 31 counties

Champaign County, IL, Clark County, IL, Clay County, IL, Coles County, IL, Crawford County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Edgar County, IL, Edwards County, IL, Effingham County, IL, Gallatin County, IL, Jasper County, IL, Lawrence County, IL, Macon County, IL, Moultrie County, IL, Piatt County, IL, Richland County, IL, Shelby County, IL, Wabash County, IL, Wayne County, IL, White County, IL, Daviess County, IN, Gibson County, IN, Knox County, IN, Pike County, IN, Posey County, IN, Sullivan County, IN, Vanderburgh County, IN, Vigo County, IN, Warrick County, IN

The radar

The Evansville,IN radar (KVWX), 121 km from the middle of the area, began a volume at 17:14 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.

Severe Thunderstorm Watch 543Jul 31, 1:15 PM CDT

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 5.2 hours before the alert went out and 102 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: 2241 J/kg
Mixed-layer CIN: -70 J/kg
Mixed-layer LCL: 958 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 19 m²/s²
0-3 km storm-relative helicity: 69 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.9

Open this sounding in Storm Lab

The text

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

167 
ACUS11 KWNS 311712
SWOMCD
SPC MCD 311711
INZ000-KYZ000-ILZ000-311815-

MESOSCALE DISCUSSION 1663
NWS STORM PREDICTION CENTER NORMAN OK
1211 PM CDT TUE JUL 31 2012

AREAS AFFECTED...PARTS OF ERN/SERN IL AND WRN/SWRN IND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 311711Z - 311815Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...A SVR TSTM WATCH IS BEING CONSIDERED FOR PARTS OF ERN IL
AND WRN IND.

TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY THIS
AFTERNOON ACROSS ERN IL INTO WRN/SWRN IND INVOF A COLD FRONT/OUTFLOW
BOUNDARY INTERSECTION AND SEWD ALONG THE OUTFLOW BOUNDARY.  DAMAGING
WINDS AND HAIL WILL BE THE PRIMARY THREATS.

DISCUSSION...LATE MORNING SURFACE ANALYSES SHOWED A COLD FRONT
ADVANCING SSEWD THROUGH SERN LOWER MI AND THE MIDWEST...WHILE A
CONVECTIVE OUTFLOW BOUNDARY FROM AN EARLY MORNING SRN GREAT LAKES
MCS INTERSECTED THE COLD FRONT IN NORTH CENTRAL IL /INVOF LIVINGSTON
AND MCLEAN COUNTIES/.  THIS OUTFLOW BOUNDARY THEN ARCED SEWD THROUGH
SERN IL TO FAR SRN IND AND THEN NEWD THROUGH FAR N CENTRAL KY TO SRN
AND ERN OH.  REGIONAL RADAR/SATELLITE IMAGERY AND LIGHTNING DATA
INDICATED A TSTM HAD FORMED BETWEEN 1640-17Z ALONG THE BORDER OF
NERN MCLEAN AND LIVINGSTON COUNTIES...WHILE A NEW CONVECTIVE UPDRAFT
WAS FORMING IMMEDIATELY UPSTREAM AS THE INITIAL STORM MOVED SEWD.

STRONG SURFACE HEATING AND COOL MIDLEVEL TEMPERATURES /AROUND -10 C
PER 12Z SOUNDING ANALYSIS/ WERE RESULTING IN MODERATE-STRONG
DESTABILIZATION WITH MLCAPE UP TO 2000 J/KG THUS FAR.  ADDITIONAL
SUSTAINED UPDRAFTS ARE EXPECTED TO DEVELOP ALONG THE COLD FRONT/
OUTFLOW INTERSECTION AS THE FRONT ADVANCES SSEWD THIS AFTERNOON.
EFFECTIVE BULK SHEAR OF 40-45 KT ACROSS THIS REGION COMBINED WITH
THE STRONG INSTABILITY AND STEEP LAPSE RATES WILL PROMOTE THE
POTENTIAL FOR SEVERE STORMS WITH DAMAGING WINDS AND HAIL THE PRIMARY
THREATS.

..PETERS/THOMPSON.. 07/31/2012

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

ATTN...WFO...LMK...IND...PAH...LOT...ILX...LSX...

LAT...LON   40368874 40428812 39708749 38578699 37928703 37658822
            38698891 39948934 40368874

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 31, 12:39 AM CDT	Mesoscale Discussion	SPC	Lake, McHenry	96 min
Jul 31, 1:13 PM CDT	Severe Thunderstorm Watch	SPC	Champaign, Clark, Clay, Coles, Crawford, Cumberland and 19 more	6 hr
Jul 31, 3:35 PM CDT	Mesoscale Discussion	SPC	Champaign, Clark, Clay, Coles, Crawford, Cumberland and 16 more	55 min
Jul 31, 6:42 PM CDT	Mesoscale Discussion	SPC	Crawford, Edwards, Jasper, Lawrence, Richland, Wabash and 1 more	33 min
Jul 31, 4:10 PM CDT	Mesoscale Discussion	SPC	Clark, Crawford, Dubois, Floyd, Gibson, Harrison and 7 more	65 min

Nearby

Mesoscale Discussions in Illinois, 2012 Mesoscale Discussions in Indiana, 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.