Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 647

May 1, 201211 counties in Illinois; 7 counties in Indiana

The Storm Prediction Center issued this mesoscale discussion at May 1, 2012, 3:39 PM CDT for 11 counties in Illinois; 7 counties in Indiana. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 1, 2012, 3:39 PM CDT (20:39 UTC)
Expired: May 1, 2012, 5:45 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Champaign County, IL, Clark County, IL, Coles County, IL, Cumberland County, IL, Douglas County, IL, Edgar County, IL, Jasper County, IL, Moultrie County, IL, Piatt County, IL, Shelby County, IL, Vermilion County, IL, Benton County, IN, Clay County, IN, Fountain County, IN, Parke County, IN, Vermillion County, IN, Vigo County, IN, Warren County, IN

The radar

The Lincoln radar (KILX), 117 km from the middle of the area, began a volume at 20:42 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

Lincoln, IL (KILX), launched 12:00Z, 8.7 hours before the alert went out and 70 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 660 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 123 m²/s²
0-3 km storm-relative helicity: 138 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

254 
ACUS11 KWNS 012039
SWOMCD
SPC MCD 012039 
INZ000-ILZ000-012245-

MESOSCALE DISCUSSION 0647
NWS STORM PREDICTION CENTER NORMAN OK
0339 PM CDT TUE MAY 01 2012

AREAS AFFECTED...EAST-CENTRAL IL TO WESTERN INDIANA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 012039Z - 012245Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...MONITORING FOR INCREASING SIGNS OF SURFACE BASED DEEP
CONVECTIVE DEVELOPMENT ACROSS EAST-CENTRAL IL INTO WESTERN
INDIANA...WHICH DOES REMAIN POSSIBLE THROUGH LATE AFTERNOON. SHOULD
TSTMS OCCUR/INCREASE...AT LEAST AN ISOLATED TORNADO/SEVERE HAIL RISK
WOULD EXIST.

DISCUSSION...RECENT VISIBLE SATELLITE TRENDS REFLECT A THICKENING CU
FIELD ACROSS PORTIONS OF EAST-CENTRAL/SOUTH-CENTRAL IL...ESPECIALLY
WITH A GENERAL CORRIDOR AROUND THE DECATUR/TAYLORVILLE AREAS AS OF
2030Z. THIS AREA IS IN VICINITY OF A WEST-EAST WARM/STATIONARY FRONT
ACROSS THE REGION...AND IS ON THE SOUTHERN PERIPHERY OF A MID-LEVEL
IMPULSE/MCV ACROSS NORTHERN IL. A KEY UNCERTAINTY EXISTS REGARDING
THE LIKELIHOOD/EXTENT OF DEEP CONVECTION WEST OF TORNADO WATCH
218....GIVEN THAT THE REGION WILL BEGIN TO INCREASINGLY COME UNDER
THE INFLUENCE OF SHORTWAVE RIDGING/WEAKENING MASS CONVERGENCE AS THE
AFOREMENTIONED MID-LEVEL IMPULSE CONTINUES TO SHIFT
EAST-NORTHEASTWARD AWAY FROM THE AREA. THAT SAID...A MOIST AND
MODERATELY UNSTABLE/WEAKLY CAPPED AIRMASS DOES REMAIN ACROSS THE
REGION...WITH VERTICAL SHEAR/SRH ACCENTUATED NEAR THE WARM FRONT.
INCREASING SIGNS/CONFIDENCE OF DEEP CONVECTIVE INITIATION COULD
PROMPT A WATCH ISSUANCE ACROSS IL AND/OR EXPANSION OF WW 218 ACROSS
INDIANA. CONVECTIVE TRENDS WILL BE CLOSELY MONITORED FOR A
TORNADO/HAIL THREAT THROUGH LATE AFTERNOON/EARLY EVENING.

..GUYER/MEAD.. 05/01/2012

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

ATTN...WFO...IND...LOT...ILX...LSX...

LAT...LON   39228897 40278868 40668715 39448695 38968817 39228897

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 1, 1:44 PM CDT	Mesoscale Discussion	SPC	Bartholomew, Boone, Brown, Clay, Daviess, Dearborn and 29 more	61 min
May 1, 1:44 PM CDT	Severe Thunderstorm Watch	SPC	Crawford, Dubois, Floyd, Harrison, Perry	6 hr
May 1, 2:01 PM CDT	Tornado Watch	SPC	Bartholomew, Boone, Brown, Carroll, Clark, Clay and 46 more	7 hr
May 1, 5:31 PM CDT	Tornado Watch	SPC	Dearborn, Fayette, Franklin, Ohio, Ripley, Switzerland and 2 more	5 hr
May 1, 5:55 PM CDT	Mesoscale Discussion	SPC	Bartholomew, Boone, Brown, Carroll, Clark, Clay and 32 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.