Alert archive / Illinois / Mesoscale Discussions in 2016

Mesoscale Discussion 478

April 27, 20167 counties in Illinois

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2016, 7:59 PM CDT for 7 counties in Illinois. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2016, 7:59 PM CDT (00:59 UTC)
Expired: Apr 27, 2016, 9:30 PM CDT
In force: 91 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

Counties Christian County, IL, Clay County, IL, Effingham County, IL, Fayette County, IL, Jasper County, IL, Richland County, IL, Shelby County, IL

The radar

The Lincoln radar (KILX), 119 km from the middle of the area, began a volume at 01:01 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 00:00Z, 1.0 hours before the alert went out and 109 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: 1 J/kg
Mixed-layer CIN: -253 J/kg
Mixed-layer LCL: 591 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 260 m²/s²
0-3 km storm-relative helicity: 289 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

706 
ACUS11 KWNS 280100
SWOMCD
SPC MCD 280059 
ILZ000-280230-

MESOSCALE DISCUSSION 0478
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT WED APR 27 2016

AREAS AFFECTED...PARTS OF CNTRL ILLINOIS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 280059Z - 280230Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...POTENTIAL FOR ADDITIONAL SHORT-LIVED TORNADOES...AND
PERHAPS MARGINALLY SEVERE HAIL...IS EXPECTED TO DIMINISH WITHIN THE
NEXT HOUR OR TWO.

DISCUSSION...SCATTERED THUNDERSTORMS WHICH HAVE FORMED DURING THE
PAST COUPLE OF HOURS ALONG A STALLED FRONTAL ZONE ACROSS CENTRAL
ILLINOIS HAVE EXHIBITED SUPERCELL STRUCTURES.  DESPITE THE RATHER
MODEST STRENGTH OF LOW-LEVEL FLOW FIELDS...SHEAR/BAROCLINICITY
ASSOCIATED WITH THE FRONT HAVE AUGMENTED LOW-LEVEL UPDRAFT
ROTATION...AND THE POTENTIAL FOR BRIEF TORNADOES.  THIS POTENTIAL IS
PROBABLY CONFINED TO A FAIRLY NARROW CORRIDOR ALONG THE
FRONT...WHERE LOW-LEVEL SHEAR AND BOUNDARY LAYER MOISTURE ARE
MAXIMIZED.  SOUTHERLY DEEP LAYER MEAN FLOW CONTINUES TO AID THE
GRADUAL PROPAGATION OF STORMS ACROSS THE FRONT INTO MUCH COOLER AND
MORE STABLE BOUNDARY LAYER...WHERE TORNADIC POTENTIAL SHOULD
DIMINISH.  AT THE SAME TIME...THE ONSET OF BOUNDARY LAYER COOLING
AND STABILIZATION TO THE SOUTHWEST OF THE FRONT IS EXPECTED TO
DIMINISH POTENTIAL FOR VIGOROUS ADDITIONAL NEW STORM DEVELOPMENT 
THROUGH THE 02-03Z TIME FRAME.

..KERR/HART.. 04/28/2016

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

ATTN...WFO...PAH...ILX...LSX...

LAT...LON   39778952 39578891 38918786 38618779 38458804 38708874
            39628980 39778952

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 27, 8:06 PM CDT	Mesoscale Discussion	SPC	Adams, Brown, Greene, Hancock, Pike, Schuyler and 1 more	84 min

Nearby

Mesoscale Discussions in Illinois, 2016 Every mesoscale discussion in 2016

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.