Alert archive / Illinois / Mesoscale Discussions in 2004

Mesoscale Discussion 396

April 20, 200426 counties in Illinois; 24 counties in Indiana; Scott County, Iowa

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2004, 6:00 PM CDT for 26 counties in Illinois; 24 counties in Indiana; Scott County, Iowa. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Apr 20, 2004, 6:00 PM CDT (23:00 UTC)
Expired
Apr 20, 2004, 8:00 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
All 51 counties

Scott County, IA, Bureau County, IL, Champaign County, IL, DeWitt County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Henry County, IL, Iroquois County, IL, Kankakee County, IL, Knox County, IL, LaSalle County, IL, Livingston County, IL, Logan County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McLean County, IL, Peoria County, IL, Piatt County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Tazewell County, IL, Vermilion County, IL, Warren County, IL, Woodford County, IL, Benton County, IN, Boone County, IN, Carroll County, IN, Cass County, IN, Clinton County, IN, Fountain County, IN, Fulton County, IN, Hamilton County, IN, Hendricks County, IN, Howard County, IN, Jasper County, IN, Johnson County, IN, Marion County, IN, Miami County, IN, Montgomery County, IN, Newton County, IN, Parke County, IN, Pulaski County, IN, Putnam County, IN, Tippecanoe County, IN, Tipton County, IN, Vermillion County, IN, Warren County, IN, White County, IN

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 11.0 hours before the alert went out and 49 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-pSkew-T log-p diagram, Lincoln, IL at 12:00Z on 2004-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lincoln, IL at 12:00Z on 2004-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 111 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1297 m above ground
0-6 km bulk shear
33 kt
0-1 km storm-relative helicity
111 m²/s²
0-3 km storm-relative helicity
169 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.

526 
ACUS11 KWNS 202301
SWOMCD
SPC MCD 202300 
INZ000-ILZ000-IAZ000-210100-

MESOSCALE DISCUSSION 0396
NWS STORM PREDICTION CENTER NORMAN OK
0600 PM CDT TUE APR 20 2004

AREAS AFFECTED...CENTRAL/NRN IL AND CENTRAL/NRN IND

CONCERNING...TORNADO WATCH 95...

VALID 202300Z - 210100Z

THE THREAT OF LOW-TOPPED SUPERCELLS CAPABLE OF PRODUCING TORNADOES
CONTINUES IN VICINITY OF WARM FRONT EXTENDING WEST-EAST ACROSS THE
WW 95 AREA. FRONT EXTENDS FROM ROUGHLY 25 NE MLI TO 45 S CGX TO 45
NW MIE AT 23Z. WARM FRONT WILL CONTINUE TO SHIFT NEWD DURING THE
EVENING HOURS...WITH LOW-LEVEL WARM ADVECTION ALLOWING FOR
SUFFICIENT DESTABILIZATION TO SUPPORT SEVERE THUNDERSTORMS INTO
PORTIONS OF NRN IL AND NRN IND. SBCAPE VALUES OF 1000-1500 J/KG ARE
PRESENT IN VICINITY OF SCATTERED SUPERCELLS ACROSS CENTRAL IL EWD
INTO IND VICINITY. LOW-LEVEL HODOGRAPH CURVATURE IS VERY IMPRESSIVE
PER IND VAD WIND PROFILE...CONTRIBUTING TO 0-3KM SRH VALUES IN
EXCESS OF 400 M2/S2 ALONG THE WARM FRONT. DESPITE MARGINAL
CAPE...LOW LCL HEIGHT ENVIRONMENT COMBINED WITH VERY FAVORABLE
LOW-LEVEL SHEAR WILL HELP TO SUSTAIN LOW TOPPED SUPERCELLS WITH
TORNADOES DURING THE NEXT 2-3 HOURS.

..BANACOS.. 04/20/2004

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

ATTN...WFO...IWX...IND...LOT...ILX...DVN...

40249072 41829071 41048597 39458599

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 20, 5:40 PM CDTTornado WatchSPCBureau, Champaign, DeWitt, Ford, Fulton, Grundy and 20 more5 hr
Apr 20, 4:40 PM CDTSevere Thunderstorm WatchSPCAppanoose, Clarke, Davis, Decatur, Henry, Jefferson and 13 more5 hr
Apr 20, 6:25 PM CDTSevere Thunderstorm WatchSPCFremont, Harrison, Mills, Monona, Montgomery, Page and 2 more5 hr

Nearby

Mesoscale Discussions in Illinois, 2004Mesoscale Discussions in Indiana, 2004Mesoscale Discussions in Iowa, 2004Every mesoscale discussion in 2004

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.