Alert archive / Illinois / Mesoscale Discussions in 2012
Mesoscale Discussion 707
The Storm Prediction Center issued this mesoscale discussion at May 4, 2012, 10:18 PM CDT for 17 counties in Illinois; 10 counties in Missouri. It was in force for 87 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2012, 10:18 PM CDT (03:18 UTC)
- Expired
- May 4, 2012, 11:45 PM CDT
- In force
- 87 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
All 27 counties
Bond County, IL, Calhoun County, IL, Clinton County, IL, Franklin County, IL, Greene County, IL, Hamilton County, IL, Jefferson County, IL, Jersey County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Monroe County, IL, Perry County, IL, Pike County, IL, Randolph County, IL, Saint Clair County, IL, Washington County, IL, Audrain County, MO, City of Saint Louis, MO, Lincoln County, MO, Monroe County, MO, Montgomery County, MO, Pike County, MO, Ralls County, MO, Saint Charles County, MO, Saint Louis County, MO, Warren County, MO
The radar
The St Louis radar (KLSX), 34 km from the middle of the area, began a volume at 03:19 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 00:00Z, 3.3 hours before the alert went out and 207 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
- 188 J/kg
- Mixed-layer CIN
- -108 J/kg
- Mixed-layer LCL
- 1330 m above ground
- 0-6 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- -3 m²/s²
- 0-3 km storm-relative helicity
- 155 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.1
The text
As transmitted, in the capitals the NWS used until 2016.
727
ACUS11 KWNS 050319
SWOMCD
SPC MCD 050318
ILZ000-MOZ000-050445-
MESOSCALE DISCUSSION 0707
NWS STORM PREDICTION CENTER NORMAN OK
1018 PM CDT FRI MAY 04 2012
AREAS AFFECTED...EAST CENTRAL MO/SW IL
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 050318Z - 050445Z
PROBABILITY OF WATCH ISSUANCE...60 PERCENT
SUMMARY...RISK FOR AT LEAST ISOLATED LARGE HAIL/DAMAGING WINDS WILL
INCREASE GRADUALLY THE NEXT FEW HOURS ACROSS ERN MO AND SWRN
IL...WHERE A SEVERE THUNDERSTORM WATCH MAY NEED TO BE CONSIDERED.
DISCUSSION...WAA IS SLOWLY STRENGTHENING IN CONJUNCTION WITH A 30-35
KT SWLY LLJ ACROSS MO...WITH THE WAA FOCUSED ALONG A STALLED FRONT.
A FEED OF MODERATE-STRONG INSTABILITY REMAINS IMMEDIATELY UPSTREAM
OF THIS BOUNDARY...WHICH SUGGESTS THAT STORM COVERAGE WILL LIKELY
INCREASE DURING THE NEXT FEW HOURS. ADDITIONALLY...STORM COVERAGE
COULD BE AIDED OVERNIGHT BY THE APPROACH OF A SHORTWAVE TROUGH FROM
SW MO/NW AR. STEEP MIDLEVEL LAPSE RATES AND MUCAPE OF 2000-3000
J/KG WILL SUPPORT A RISK FOR LARGE HAIL...IN AN ENVIRONMENT WITH
SUFFICIENT VERTICAL SHEAR FOR ORGANIZED MULTICELL CLUSTERS AND SOME
TRANSIENT SUPERCELL STRUCTURES. DAMAGING WINDS COULD ALSO BECOME A
CONCERN ONCE STORM COVERAGE INCREASES AND CELL MERGERS PROMOTE SOME
UPSCALE GROWTH OF CONVECTION. THE ERN MO/SWRN IL AREA WILL CONTINUE
TO BE MONITORED...AND THE SEVERE STORM RISK COULD BECOME SUFFICIENT
TO WARRANT A SEVERE THUNDERSTORM WATCH.
..THOMPSON.. 05/05/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PAH...ILX...LSX...
LAT...LON 38759162 39239207 39559204 39719167 39739151 39739115
39529035 39248985 38868910 38548869 38228842 38008847
37838889 37928955 38329064 38759162SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 7:57 PM CDT | Mesoscale Discussion | SPC | Bond, Calhoun, Christian, Clay, Clinton, Crawford and 25 more | 63 min |
| May 4, 10:35 PM CDT | Severe Thunderstorm Watch | SPC | Bond, Calhoun, Clinton, Edwards, Fayette, Franklin and 24 more | 8 hr |
| May 5, 12:55 AM CDT | Mesoscale Discussion | SPC | Edwards, Gallatin, Hamilton, Hardin, Saline, Wabash and 1 more | 95 min |
| May 5, 5:06 AM CDT | Mesoscale Discussion | SPC | Gallatin, Hardin, White | 114 min |
Nearby
Mesoscale Discussions in Illinois, 2012Mesoscale Discussions in Missouri, 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.