Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 248

March 12, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Mar 12, 2012, 11:03 AM CDT for 4 states. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Mar 12, 2012, 11:03 AM CDT (16:03 UTC)
Expired: Mar 12, 2012, 12:00 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center

All 22 counties

Boone County, IL, Bureau County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Henry County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Will County, IL, Lake County, IN, LaPorte County, IN, Porter County, IN, Saint Joseph County, IN, Allegan County, MI, Berrien County, MI, Cass County, MI, Van Buren County, MI, Kenosha County, WI

The radar

The Chicago radar (KLOT), 45 km from the middle of the area, began a volume at 16:04 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, 4.1 hours before the alert went out and 197 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: 70 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 523 m above ground
0-6 km bulk shear: 73 kt
0-1 km storm-relative helicity: 90 m²/s²
0-3 km storm-relative helicity: 85 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

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

517 
ACUS11 KWNS 121603
SWOMCD
SPC MCD 121603 
MIZ000-INZ000-ILZ000-WIZ000-121700-

MESOSCALE DISCUSSION 0248
NWS STORM PREDICTION CENTER NORMAN OK
1103 AM CDT MON MAR 12 2012

AREAS AFFECTED...NRN IL...FAR SERN WI...FAR SWRN LOWER MI...NWRN IND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 121603Z - 121700Z

DMGG WIND THREAT SHOULD SLOWLY INCREASE THROUGH EARLY AFTERNOON FROM
PORTIONS OF NRN IL/SERN WI EWD TOWARDS SWRN LWR MI. A WW DOES NOT
APPEAR IMMINENT PRIMARILY OWING TO MARGINAL INSTABILITY...BUT
CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED FOR A POSSIBLE WW
THIS AFTERNOON.

A NARROW ZONE OF ASCENT FOCUSED ALONG THE SERN PERIPHERY OF A CLOSED
UPPER MIDWEST LOW HAS SUPPORTED A LINE OF TSTMS EXTENDING FROM 20 SE
MLI TO 30 E JVL. THIS ACTIVITY WAS LOCATED JUST W OF A LOW-LEVEL
MOISTURE AXIS...WITH MID-UPPER 50S DEW POINTS SLOWLY ADVECTING NWD
INTO SRN WI. PARTIAL CLEARING OVER NERN IL/SERN WI IS ALLOWING
TEMPERATURES TO REACH THE LOW 60S...YIELDING MLCAPE VALUES OF
200-500 J/KG. ADDITIONALLY...WEAK INHIBITION WAS NOTED IN 12Z
DVN/ILX SOUNDINGS...SUGGESTING CONVECTION IS LIKELY ROOTED NEAR THE
SFC ATTM. BACKGROUND FLOW FIELDS ARE QUITE STRONG /40-50 KTS 0.5-3
KM AGL LAYER MEAN FLOW AS SAMPLED BY LOT/ILX VWP/...AND WITH NEARLY
UNIDIRECTIONAL LOWER-TROPOSPHERIC WIND FIELDS...PRIMARY THREAT
THROUGH EARLY AFTERNOON APPEARS TO BE DMGG WINDS...BUT A BRIEF/WEAK
TOR THREAT MAY EXIST GIVEN MODERATELY STRONG 0-1 KM SHEAR AND A
MOIST BOUNDARY LAYER/LOW LCL/S. A WW IS NOT CURRENTLY
ANTICIPATED...WITH MARGINAL INSTABILITY BEING THE PRIMARY FACTOR
PRECLUDING A MORE SIGNIFICANT DMGG WIND THREAT ATTM...BUT CONVECTIVE
TRENDS WILL CONTINUE TO BE MONITORED.

..ROGERS.. 03/12/2012

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

ATTN...WFO...IWX...GRR...LOT...ILX...MKX...DVN...

LAT...LON   42728790 42658679 42378593 41968586 41508612 41398818
            41288902 41148983 41149026 41469016 41978941 42388886
            42628839 42748807 42728790

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 12, 3:22 PM CDT	Tornado Watch	SPC	DeKalb, Elkhart, Kosciusko, LaGrange, LaPorte, Marshall and 4 more	7 hr
Mar 12, 5:29 PM CDT	Mesoscale Discussion	SPC	LaGrange, Steuben	91 min
Mar 12, 6:36 PM CDT	Tornado Watch	SPC	Genesee, Huron, Lapeer, Lenawee, Livingston, Macomb and 7 more	7 hr

Nearby

Mesoscale Discussions in Illinois, 2012 Mesoscale Discussions in Indiana, 2012 Mesoscale Discussions in Michigan, 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.