Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 1773

August 16, 201246 counties in Illinois; 42 counties in Indiana; 8 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Aug 16, 2012, 12:47 PM CDT for 46 counties in Illinois; 42 counties in Indiana; 8 counties in Missouri. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued: Aug 16, 2012, 12:47 PM CDT (17:47 UTC)
Expired: Aug 16, 2012, 2:15 PM CDT
In force: 88 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 96 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, Greene County, IL, Hamilton County, IL, Jasper County, IL, Jefferson County, IL, Jersey County, IL, Lawrence County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Menard County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Perry County, IL, Piatt County, IL, Randolph County, IL, Richland County, IL, Saint Clair County, IL, Sangamon County, IL, Scott County, IL, Shelby County, IL, Vermilion County, IL, Wabash County, IL, Washington County, IL, Wayne County, IL, White County, IL, Bartholomew County, IN, Boone County, IN, Brown County, IN, Clay County, IN, Clinton County, IN, Daviess County, IN, Decatur County, IN, Dubois County, IN, Fountain County, IN, Gibson County, IN, Greene County, IN, Hamilton County, IN, Hancock County, IN, Hendricks County, IN, Henry County, IN, Jackson County, IN, Jennings County, IN, Johnson County, IN, Knox County, IN, Lawrence County, IN, Madison County, IN, Marion County, IN, Martin County, IN, Monroe County, IN, Montgomery County, IN, Morgan County, IN, Orange County, IN, Owen County, IN, Parke County, IN, Pike County, IN, Posey County, IN, Putnam County, IN, Rush County, IN, Shelby County, IN, Sullivan County, IN, Tippecanoe County, IN, Tipton County, IN, Vanderburgh County, IN, Vermillion County, IN, Vigo County, IN, Warren County, IN, Washington County, IN, City of Saint Louis, MO, Franklin County, MO, Jefferson County, MO, Lincoln County, MO, Montgomery County, MO, Saint Charles County, MO, Saint Louis County, MO, Warren County, MO

The radar

The Lincoln radar (KILX), 124 km from the middle of the area, began a volume at 17:50 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.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 5.8 hours before the alert went out and 106 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: 817 J/kg
Mixed-layer CIN: -262 J/kg
Mixed-layer LCL: 1559 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 36 m²/s²
0-3 km storm-relative helicity: 69 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.0

Open this sounding in Storm Lab

The text

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

334 
ACUS11 KWNS 161747
SWOMCD
SPC MCD 161747 
INZ000-ILZ000-MOZ000-161915-

MESOSCALE DISCUSSION 1773
NWS STORM PREDICTION CENTER NORMAN OK
1247 PM CDT THU AUG 16 2012

AREAS AFFECTED...E CNTRL MO...PARTS OF CNTRL/SRN IL AND IND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 161747Z - 161915Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...SEVERE WIND POTENTIAL THROUGH 20-21Z APPEARS LOW...BUT THE
NEED FOR A WW MAY NOT BE OUT OF THE QUESTION LATER THIS AFTERNOON OR
EVENING.

DISCUSSION...VIGOROUS NEW CONVECTIVE DEVELOPMENT ACROSS CENTRAL
ILLINOIS APPEARS MOSTLY IN RESPONSE TO LOWER/MID TROPOSPHERIC WARM
ADVECTION CORRESPONDING TO STRONG 2-HOUR SURFACE PRESSURE FALLS...
IN THE WAKE OF THE CONVECTIVE SYSTEM WEAKENING ACROSS MICHIGAN AND
INDIANA.  STILL AHEAD OF THE FRONT...LINGERING LOW-LEVEL
MOISTURE...RELATIVELY STEEP MID-LEVEL LAPSE RATES...AND STRONG
VERTICAL SHEAR BENEATH 40-50 KT WESTERLY 500 MB FLOW...SUPPORT
POTENTIAL FOR HAIL IN STRONGER CELLS.  HOWEVER...WESTERLY DEEP LAYER
MEAN FLOW LIKELY WILL REMAIN PROMINENT IN TENDING TO ADVECT ACTIVITY
ACROSS THE EXPANDING RESIDUAL DOWNSTREAM SURFACE COLD POOL.  THIS IS
EXPECTED TO LIMIT DAMAGING WIND POTENTIAL...PARTICULARLY IN THE
PRESENCE OF RATHER MODEST...AND WEAKENING...AMBIENT LOW-LEVEL /850
MB/ WIND FIELDS.

ADDITIONAL SCATTERED STRONG BOUNDARY LAYER BASED STORM DEVELOPMENT
MAY NOT BE OUT OF THE QUESTION LATER THIS AFTERNOON IN CLOSER
PROXIMITY TO THE OUTFLOW BOUNDARY ACROSS PARTS OF SOUTHERN INDIANA
AND ILLINOIS...INTO THE VICINITY OF ITS INTERSECTION WITH THE COLD
FRONT ADVANCING SOUTHEASTWARD ACROSS PARTS OF WEST CENTRAL ILLINOIS
AND EAST CENTRAL MISSOURI.  GENERALLY SOUTH OF STRONGER
WESTERLIES...AND MID-LEVEL FORCING FOR ASCENT SPREADING ACROSS THE
GREAT LAKES REGION...SUPPORT FOR UPSCALE GROWTH WITH ORGANIZED
SEVERE WEATHER POTENTIAL IS MORE UNCERTAIN.  BUT...BOUNDARY LAYER
CAPE WILL BE SIZABLE...AND IT MAY NOT BE OUT OF THE QUESTION THAT
THE BOUNDARY INTERSECTION COULD PROVIDE THE FOCUS FOR ANOTHER
EXPANDING STORM CLUSTER.

..KERR/CARBIN.. 08/16/2012

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

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

LAT...LON   39059163 40268963 40548750 40238550 39818531 38738565
            37978765 38009043 38299108 39059163

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 16, 3:57 AM CDT	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 19 more	3 hr
Aug 16, 10:01 AM CDT	Mesoscale Discussion	SPC	Clark, Coles, Crawford, Cumberland, Douglas, Edgar and 4 more	89 min
Aug 16, 1:05 PM CDT	Severe Thunderstorm Watch	SPC	Bond, Brown, Calhoun, Cass, Champaign, Christian and 36 more	7 hr
Aug 16, 3:07 PM CDT	Mesoscale Discussion	SPC	Clark, Clay, Coles, Crawford, Cumberland, Edwards and 8 more	83 min
Aug 16, 3:27 PM CDT	Severe Thunderstorm Watch	SPC	Alexander, Clark, Crawford, Edwards, Franklin, Gallatin and 14 more	8 hr
Aug 16, 5:25 PM CDT	Mesoscale Discussion	SPC	Alexander, Bond, Clark, Clay, Clinton, Crawford and 27 more	2 hr

Nearby

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