Alert archive / Illinois / Mesoscale Discussions in 2011
Mesoscale Discussion 1995
The Storm Prediction Center issued this mesoscale discussion at Aug 17, 2011, 3:44 PM CDT for 53 counties in Illinois; 4 counties in Iowa; Clark County, Missouri. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Aug 17, 2011, 3:44 PM CDT (20:44 UTC)
- Expired
- Aug 17, 2011, 5:15 PM CDT
- In force
- 91 min
- Issued by
- the Storm Prediction Center
All 58 counties
Clinton County, IA, Des Moines County, IA, Lee County, IA, Scott County, IA, Adams County, IL, Boone County, IL, Brown County, IL, Bureau County, IL, Calhoun County, IL, Carroll County, IL, Cass County, IL, Christian County, IL, DeKalb County, IL, DeWitt County, IL, DuPage County, IL, Ford County, IL, Fulton County, IL, Greene County, IL, Grundy County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Macon County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McHenry County, IL, McLean County, IL, Menard County, IL, Mercer County, IL, Morgan County, IL, Ogle County, IL, Peoria County, IL, Piatt County, IL, Pike County, IL, Putnam County, IL, Rock Island County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Stark County, IL, Stephenson County, IL, Tazewell County, IL, Warren County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL, Clark County, MO
The radar
The Lincoln radar (KILX), 84 km from the middle of the area, began a volume at 20:50 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 nearest sounding before it
Davenport, (KDVN), launched 12:00Z, 8.7 hours before the alert went out and 114 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
- 301 J/kg
- Mixed-layer CIN
- -111 J/kg
- Mixed-layer LCL
- 928 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 82 m²/s²
- 0-3 km storm-relative helicity
- 72 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
The text
As transmitted, in the capitals the NWS used until 2016.
752
ACUS11 KWNS 172045
SWOMCD
SPC MCD 172044
ILZ000-WIZ000-IAZ000-MOZ000-172215-
MESOSCALE DISCUSSION 1995
NWS STORM PREDICTION CENTER NORMAN OK
0344 PM CDT WED AUG 17 2011
AREAS AFFECTED...CNTRL/NRN IL...FAR NERN MO...FAR ERN IA...FAR SRN
WI
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 172044Z - 172215Z
A FEW STORMS COULD PRODUCE DMGG WIND GUSTS AND/OR LARGE HAIL THIS
AFTERNOON INTO THE EVENING. HOWEVER...THE ANTICIPATED ISOLATED
NATURE OF THE SVR THREAT IS EXPECTED TO PRECLUDE THE NEED FOR A WW.
MID-AFTERNOON SFC MESOANALYSIS DEPICTS A COLD FRONT EXTENDING FROM
SWRN WI INTO CNTRL IA...ACROSS WHICH A MODEST THERMAL GRADIENT
EXISTS -- I.E. TEMPERATURES IN THE UPPER 70S AND LOWER 80S IN ITS
WAKE AND IN THE MID AND UPPER 80S PRECEDING IT. A PREFRONTAL WIND
SHIFT AXIS LIES NEAR THE IL/IA BORDER...SEPARATING NWLY FLOW TO ITS
WEST FROM FLOW WITH MORE OF A SLY COMPONENT TO ITS EAST. MODIFIED
12Z DAVENPORT RAOB FOR CURRENT CONDITIONS SUGGESTS MLCAPE VALUES ON
THE ORDER OF 1500-2000 J/KG INVOF THE WIND SHIFT AXIS...ALONG WHICH
WEAK SFC CONVERGENCE COULD SUPPORT THE DEVELOPMENT OF ISOLATED TO
SCATTERED CONVECTION DURING THE NEXT FEW HOURS. THE AFOREMENTIONED
BUOYANCY COMBINED WITH 30-45 KT OF EFFECTIVE BULK SHEAR BENEATH A
MID-LEVEL WNWLY/NWLY SPEED MAX OVER THE MID-MISSISSIPPI VALLEY
REGION...COULD SUPPORT A FEW SUSTAINED/ORGANIZED STORM STRUCTURES
WITH AN ATTENDANT THREAT FOR LARGE HAIL AND/OR DMGG WIND GUSTS.
HOWEVER...SFC OBS...ALONG WITH DAVENPORT/ST LOUIS/CHICAGO VWP
DATA...DEPICT WEAK LOW-LEVEL FLOW ACROSS THE REGION -- I.E. WIND
SPEEDS AOB 10 KT BELOW THE 1-KM-AGL-LEVEL -- OFFERING RATHER WEAK
CONVERGENCE ALONG THE AFOREMENTIONED SFC FEATURES. THIS SHOULD LIMIT
STORM COVERAGE TO SOME DEGREE. FURTHERMORE...THE SHALLOW/WEAK NATURE
OF THE CONVERGENCE AND RECENT INFLUX OF A MID-LEVEL DRY SLOT PER
WATER VAPOR IMAGERY SHOULD MITIGATE THE SVR POTENTIAL...WITH THE SVR
THREAT EXPECTED TO REMAIN ISOLATED.
..COHEN.. 08/17/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...ILX...MKX...LSX...DVN...
LAT...LON 41458760 40318817 39338952 39159068 39479139 40249180
40879154 42349026 42698873 42458779 41458760Nearby
Mesoscale Discussions in Illinois, 2011Mesoscale Discussions in Iowa, 2011Mesoscale Discussions in Missouri, 2011Every mesoscale discussion in 2011
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.