Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 554

April 15, 201231 counties in Illinois

The Storm Prediction Center issued this mesoscale discussion at Apr 15, 2012, 6:12 PM CDT for 31 counties in Illinois. It was in force for 63 min.

The area

The outline as issued.

The facts

Issued: Apr 15, 2012, 6:12 PM CDT (23:12 UTC)
Expired: Apr 15, 2012, 7:15 PM CDT
In force: 63 min
Issued by: the Storm Prediction Center

All 31 counties

Boone County, IL, Bureau County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Henry County, IL, Iroquois 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, Marshall County, IL, McHenry County, IL, McLean County, IL, Ogle County, IL, Peoria County, IL, Putnam County, IL, Stark County, IL, Tazewell County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL

The radar

The Chicago radar (KLOT), 48 km from the middle of the area, began a volume at 23:15 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

Lincoln, IL (KILX), launched 12:00Z, 11.2 hours before the alert went out and 148 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: 17 J/kg
Mixed-layer CIN: -265 J/kg
Mixed-layer LCL: 1124 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 404 m²/s²
0-3 km storm-relative helicity: 425 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

611 
ACUS11 KWNS 152313
SWOMCD
SPC MCD 152312
INZ000-ILZ000-WIZ000-160015-

MESOSCALE DISCUSSION 0554
NWS STORM PREDICTION CENTER NORMAN OK
0612 PM CDT SUN APR 15 2012

AREAS AFFECTED...NRN IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 152312Z - 160015Z

PORTIONS OF NRN IL ARE BEING MONITORED FOR A POSSIBLE WW.
CONSIDERABLE UNCERTAINTY REGARDING TSTM INTENSITY/COVERAGE
EXISTS...BUT CONVECTIVE TRENDS ARE BEING CLOSELY MONITORED.

ISOLATED TSTMS HAVE DEVELOPED OVER THE PAST HR SW OF THE CHICAGO
METRO AREA...WITHIN A BROAD LOW-LEVEL WAA REGIME AHEAD OF A STRONG
CNTRL PLAINS CYCLONE. A LACK OF DISCERNABLE MESOSCALE BOUNDARIES IS
LEADING TO LARGELY UNFOCUSED DEVELOPMENT OF NEW
CONVECTION...YIELDING CONSIDERABLE UNCERTAINTY TO EVOLUTION AND
EVENTUAL COVERAGE OF THE POTENTIAL THREAT. HOWEVER...THE ENVIRONMENT
ACROSS THIS AREA IS STRONGLY SHEARED /0-1 KM BULK SHEAR NEAR 30 KTS
PER LOT VWP/...SUPPORTIVE OF DMGG WIND GUSTS AND PERHAPS A TORNADO
SHOULD CONVECTION CONTINUE TO INTENSIFY. FORECAST MODEL GUIDANCE
ALSO INDICATES LLJ SHOULD CONTINUE TO STRENGTHEN THROUGH AT LEAST
04Z...WHILE STORMS WILL HAVE THE POTENTIAL TO REMAIN NEAR SFC-BASED.
INSTABILITY REMAINS SOMEWHAT OF A LIMITING FACTOR /NEAR 1000 J/KG
MLCAPE PER RUC OBJECTIVE ANALYSIS/ AS WIDESPREAD STRATUS OBSERVED ON
VISIBLE SATELLITE LOOP HAS LIKELY LIMITED DIABATIC HEATING SOMEWHAT.
CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED FOR ISSUANCE OF A
POTENTIAL WW.

..ROGERS.. 04/15/2012

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

ATTN...WFO...LOT...ILX...MKX...DVN...

LAT...LON   41678750 41168765 40588772 40358867 40349024 41179038
            42159006 42508929 42448813 42268780 41678750

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 14, 8:41 PM CDT	Severe Thunderstorm Watch	SPC	Bureau, Carroll, Henderson, Henry, Mercer, Putnam and 3 more	4 hr
Apr 14, 9:54 PM CDT	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, DeKalb, DuPage, Henry and 12 more	96 min
Apr 15, 4:22 PM CDT	Mesoscale Discussion	SPC	Bond, Brown, Calhoun, Cass, Christian, Clinton and 31 more	83 min
Apr 15, 4:42 PM CDT	Tornado Watch	SPC	Adams, Bond, Brown, Calhoun, Cass, Clinton and 15 more	6 hr

Nearby

Mesoscale Discussions in Illinois, 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.