Alert archive / Illinois / Mesoscale Discussions in 2012
Mesoscale Discussion 853
The Storm Prediction Center issued this mesoscale discussion at May 20, 2012, 3:50 PM CDT for 4 counties in Illinois; Walworth County, Waukesha County, Wisconsin. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- May 20, 2012, 3:50 PM CDT (20:50 UTC)
- Expired
- May 20, 2012, 5:15 PM CDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
Counties DeKalb County, IL, DuPage County, IL, Kane County, IL, McHenry County, IL, Walworth County, WI, Waukesha County, WI
The radar
The Milwaukee radar (KMKX), 61 km from the middle of the area, began a volume at 20:51 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
Davenport, (KDVN), launched 12:00Z, 8.8 hours before the alert went out and 213 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
- 693 J/kg
- Mixed-layer CIN
- -150 J/kg
- Mixed-layer LCL
- 1669 m above ground
- 0-6 km bulk shear
- 19 kt
- 0-1 km storm-relative helicity
- 39 m²/s²
- 0-3 km storm-relative helicity
- 29 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
179 ACUS11 KWNS 202050 SWOMCD SPC MCD 202050 ILZ000-WIZ000-202215- MESOSCALE DISCUSSION 0853 NWS STORM PREDICTION CENTER NORMAN OK 0350 PM CDT SUN MAY 20 2012 AREAS AFFECTED...NERN IL THROUGH SERN WI CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 202050Z - 202215Z PROBABILITY OF WATCH ISSUANCE...40 PERCENT SUMMARY...STORMS HAVE BECOME A LITTLE BETTER ORGANIZED AS A LINE SEGMENT OVER NCNTRL IL. THIS ACTIVITY WILL POSE A RISK FOR DAMAGING WIND AS IT MOVES INTO NERN IL AND SERN WI. TRENDS ARE BEING MONITORED FOR A POSSIBLE WW. DISCUSSION...STORMS DEVELOPING ALONG A PRE-FRONTAL CONVERGENCE AXIS HAVE BECOME BETTER ORGANIZED AS A LINE SEGMENT. ACTIVITY IS FORMING WITHIN AN ENVIRONMENT CHARACTERIZED BY 30-35F BOUNDARY LAYER TEMPERATURE-DEWPOINT SPREADS...STEEP LOW-MID LEVEL LAPSE RATES AND MODERATE /1000-1500 J/KG/ INSTABILITY. THIS ENVIRONMENT IS FAVORABLE FOR ISOLATED STRONG TO DAMAGING WIND GUSTS...ESPECIALLY WITH STORMS THAT HAVE HIGHER REFLECTIVITY CORES ABOVE 5 KM. CONCERN IS THAT AS STORMS BECOME MORE LINEAR...THE THREAT MAY BECOME A LITTLE MORE WIDESPREAD. ..DIAL/WEISS.. 05/20/2012 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LOT...MKX... LAT...LON 43078792 42098789 41728814 41868896 43088833 43078792
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 20, 1:17 PM CDT | Mesoscale Discussion | SPC | Boone, Brown, Bureau, Carroll, Cass, DeKalb and 32 more | 118 min |
| May 20, 1:33 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Clinton, Franklin, Gallatin, Hamilton and 18 more | 87 min |
| May 20, 10:52 AM CDT | Mesoscale Discussion | SPC | Adams, Clark, Florence, Forest, Jackson, Juneau and 18 more | 113 min |
| May 20, 12:24 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Brown, Calumet, Clark, Door, Florence and 24 more | 7 hr |
| May 20, 2:57 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Calumet, Florence, Forest, Langlade and 12 more | 2 hr |
Nearby
Mesoscale Discussions in Illinois, 2012Mesoscale Discussions in Wisconsin, 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.