Alert archive / Illinois / Mesoscale Discussions in 2012
Mesoscale Discussion 1849
The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2012, 12:41 PM CDT for 42 counties in Illinois. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2012, 12:41 PM CDT (17:41 UTC)
- Expired
- Sep 1, 2012, 1:45 PM CDT
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 95%
All 42 counties
Bond County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, Clay County, IL, Clinton County, IL, Coles County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Effingham County, IL, Fayette County, IL, Franklin County, IL, Fulton County, IL, Hamilton County, IL, Jackson County, IL, Jasper County, IL, Jefferson County, IL, Knox County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Marion County, IL, Marshall County, IL, Mason County, IL, McLean County, IL, Menard County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Peoria County, IL, Perry County, IL, Piatt County, IL, Richland County, IL, Sangamon County, IL, Shelby County, IL, Stark County, IL, Tazewell County, IL, Washington County, IL, Wayne County, IL, White County, IL, Woodford County, IL
The radar
The Lincoln radar (KILX), 38 km from the middle of the area, began a volume at 17:43 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, 5.7 hours before the alert went out and 75 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.
- Mixed-layer CAPE
- 443 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 457 m above ground
- 0-6 km bulk shear
- 14 kt
- 0-1 km storm-relative helicity
- 24 m²/s²
- 0-3 km storm-relative helicity
- 36 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
272
ACUS11 KWNS 011741
SWOMCD
SPC MCD 011741
ILZ000-MOZ000-011845-
MESOSCALE DISCUSSION 1849
NWS STORM PREDICTION CENTER NORMAN OK
1241 PM CDT SAT SEP 01 2012
AREAS AFFECTED...IL
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 011741Z - 011845Z
PROBABILITY OF WATCH ISSUANCE...95 PERCENT
SUMMARY...AFTERNOON HEATING WILL CONTRIBUTE TO FURTHER
DESTABILIZATION ACROSS IL YIELDING AN INCREASING THREAT FOR ISOLATED
TORNADOES AND PERHAPS LOCALLY DAMAGING WINDS.
DISCUSSION...REMNANTS OF TROPICAL SYSTEM ISAAC ARE DRIFTING SLOWLY
EWD ACROSS MO EARLY THIS AFTERNOON. DOWNSTREAM...PARTIAL BREAKS IN
CLOUD COVER HAVE CONTRIBUTED TO STEEPENING LOW LEVEL LAPSE RATES
WITHIN THE BOUNDARY LAYER ACROSS IL. THIS APPEARS TO BE MOSTLY
RESPONSIBLE FOR INCREASE IN SMALL DISCRETE SHOWERS THAT HAVE
DEVELOPED ACROSS MUCH OF CNTRL IL WITHIN FAVORABLY MOIST BUT
MARGINALLY SHEARED ENVIRONMENT. SEVERAL REPORTS OF TORNADOES HAVE
BEEN NOTED WITH THESE SMALL SHOWERS AND ADDITIONAL SHORT-LIVED WEAK
TORNADOES COULD OCCUR.
ADDITIONALLY...A NARROW LINE OF CONVECTION IS GRADUALLY INCREASING
IN INTENSITY ACROSS WCNTRL IL AND THIS APPEARS LOOSELY CORRELATED
WITH A MID LEVEL DRY INTRUSION AND POSSIBLE MID LEVEL VORT LOBE.
ALTHOUGH LIGHTNING HAS YET TO BE NOTED WITH THIS ACTIVITY ADDITIONAL
HEATING SHOULD CONTRIBUTE TO MORE INTENSE UPDRAFTS. LOCALLY
DAMAGING WINDS MAY ULTIMATELY EVOLVE WITH THIS SQUALL LINE ALONG
WITH THE POSSIBILITY FOR ISOLATED TORNADOES.
..DARROW/CORFIDI.. 09/01/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PAH...LOT...ILX...LSX...DVN...
LAT...LON 41178890 41169004 40459066 39709026 38948985 37618961
37918817 40188786 41178890SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 31, 9:05 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Brown, Calhoun, Cass, Champaign and 39 more | 55 min |
| Sep 1, 12:46 PM CDT | Tornado Watch | SPC | Cass, Champaign, Christian, Clark, Clay, Coles and 29 more | 7 hr |
| Sep 1, 1:19 PM CDT | Tornado Watch | SPC | Alexander, Bond, Clinton, Edwards, Fayette, Franklin and 20 more | 8 hr |
| Sep 1, 3:30 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Christian, Clark, Clay, Clinton and 51 more | 60 min |
| Sep 1, 5:43 PM CDT | Mesoscale Discussion | SPC | Alexander, Gallatin, Hamilton, Hardin, Johnson, Massac and 7 more | 92 min |
Nearby
Mesoscale Discussions in Illinois, 2012Every 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.