Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 585

April 25, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Apr 25, 2012, 4:36 PM CDT for 4 states. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Apr 25, 2012, 4:36 PM CDT (21:36 UTC)
Expired: Apr 25, 2012, 6:00 PM CDT
In force: 84 min
Issued by: the Storm Prediction Center

All 102 counties

Bond County, IL, Calhoun County, IL, Champaign County, IL, Christian County, IL, Clark County, IL, Clay County, IL, Clinton 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, Fayette County, IL, Franklin County, IL, Gallatin County, IL, Greene County, IL, Hamilton County, IL, Hardin County, IL, Jackson County, IL, Jasper County, IL, Jefferson County, IL, Jersey County, IL, Johnson County, IL, Lawrence County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Massac County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Perry County, IL, Piatt County, IL, Pope County, IL, Pulaski County, IL, Randolph County, IL, Richland County, IL, Saint Clair County, IL, Saline County, IL, Sangamon County, IL, Shelby County, IL, Union County, IL, Wabash County, IL, Washington County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Clay County, IN, Crawford County, IN, Daviess County, IN, Dubois County, IN, Gibson County, IN, Greene County, IN, Harrison County, IN, Knox County, IN, Lawrence County, IN, Martin County, IN, Monroe County, IN, Orange County, IN, Owen County, IN, Parke County, IN, Perry County, IN, Pike County, IN, Posey County, IN, Spencer County, IN, Sullivan County, IN, Vanderburgh County, IN, Vermillion County, IN, Vigo County, IN, Warrick County, IN, Washington County, IN, Ballard County, KY, Breckinridge County, KY, Butler County, KY, Caldwell County, KY, Christian County, KY, Crittenden County, KY, Daviess County, KY, Hancock County, KY, Henderson County, KY, Hopkins County, KY, Livingston County, KY, Lyon County, KY, Marshall County, KY, McCracken County, KY, McLean County, KY, Meade County, KY, Muhlenberg County, KY, Ohio County, KY, Trigg County, KY, Union County, KY, Webster County, KY, City of Saint Louis, MO, Perry County, MO, Saint Charles County, MO, Saint Louis County, MO

The radar

The Evansville,IN radar (KVWX), 82 km from the middle of the area, began a volume at 21:40 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 187Apr 25, 7:45 PM CDT

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 9.6 hours before the alert went out and 180 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: 5 J/kg
Mixed-layer CIN: -495 J/kg
Mixed-layer LCL: 1292 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: 82 m²/s²
0-3 km storm-relative helicity: 174 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

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

096 
ACUS11 KWNS 252136
SWOMCD
SPC MCD 252136 
KYZ000-INZ000-ILZ000-MOZ000-252300-

MESOSCALE DISCUSSION 0585
NWS STORM PREDICTION CENTER NORMAN OK
0436 PM CDT WED APR 25 2012

AREAS AFFECTED...CNTRL IL AND SRN IL...SRN IND...WRN KY

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 252136Z - 252300Z

STORMS ARE EXPECTED TO INCREASE IN COVERAGE OVER THE NEXT FEW
HOURS...WITH MAINLY A HAIL AND WIND THREAT. A WATCH APPEARS LIKELY.

THE 18Z ILX SOUNDING SHOWED STEEP LAPSE RATES ALOFT...BUT STILL
STABLE FOR SURFACE BASED PARCELS. HOWEVER...WHEN MODIFIED FOR
CURRENT CONDITIONS...TEMPERATURES IN THE LOWER 80S F AND DEWPOINTS
APPROACHING 60 F...CIN IS NEARLY GONE. INDEED...STORMS HAVE BEGUN TO
DEVELOP OVER CNTRL IL...NEAR STATIONARY BOUNDARY AND WHERE LOW LEVEL
WARM ADVECTION PERSISTS. THIS INITIAL ACTIVITY ALREADY APPEARS TO
HAVE A HAIL AND WIND THREAT.

WITH STEEP LAPSE RATES AND 50 KT NW ORIENTED DEEP SHEAR...THIS WILL
FAVOR LONG LIVED STORMS...INCLUDING SUPERCELLS AND/OR BOWS. STORM
MODE COULD REMAIN SUPERCELLULAR IF OUTFLOW PRODUCTION IS KEPT
LOW...BUT SOME SWWD PROPAGATION IS POSSIBLE...AND MERGING OUTFLOWS
WOULD RESULT IN MORE OF A WIND THREAT.

THE MAIN DETRIMENT TO TORNADOES WILL BE THE MARGINAL LOW LEVEL
MOISTURE IN RELATION TO RELATIVELY WARM/DRY AIR FROM 850-700 MB AND
MARGINAL LCL HEIGHTS. A ROGUE TORNADO CANNOT BE RULED OUT AS
ACTIVITY CONTINUES TO EVOLVE. THE AREA FROM SRN IL INTO SWRN
IND...NEAR THE BOUNDARY BE MONITORED CLOSELY FOR ANY TORNADO
POTENTIAL.

..JEWELL.. 04/25/2012

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

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

LAT...LON   40428869 40028747 39048605 37858600 37048679 36768786
            36858879 37378952 38039024 38369061 38999082 39789033
            40428869

Nearby

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