Alert archive / Illinois / Severe Thunderstorm Warnings in 2003
Severe Thunderstorm Warning 139, NWS Chicago, IL
NWS Chicago, IL issued this severe thunderstorm warning at Jul 20, 2003, 5:57 PM CDT for Lee County, Illinois. It was in force for 48 min. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Jul 20, 2003, 5:57 PM CDT (22:57 UTC)
- Expired
- Jul 20, 2003, 6:45 PM CDT
- In force
- 48 min
- Issued by
- NWS Chicago, IL
- Area
- Counties, with a storm outline in the text
County Lee County, IL
The radar
The Chicago radar (KLOT), 102 km from the middle of the area, began a volume at 22:58 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, 11.0 hours before the alert went out and 187 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
- 649 J/kg
- Mixed-layer CIN
- -220 J/kg
- Mixed-layer LCL
- 888 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 74 m²/s²
- 0-3 km storm-relative helicity
- 115 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.2
What forecasters said that day
The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 20, 3:15 PM CDT, 2 hours 42 minutes earlier.
Area forecast discussion, Jul 20, 3:15 PM CDT, 2 hours 42 minutes before
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO IL 315 PM CDT SUN JUL 20 2003 PUBLIC DISCUSSION AFTERNOON ZONES/GRIDS: MAIN PROBLEM THIS EVENING IS WITH TSTM FCST. SPC HAS LOWERED REGION INTO SLIGHT RISK AS LO LEVEL FEATURES ARE AS YET POORLY DEFINED. SFC DEW POINTS HAVE RISEN INTO LOER 70S BUT MOISTURE CONVERGENCE REMAINS QUITE NEBULOUS ACROSS MOST OF MIDWEST. CONVECTIVE DEBRIS HAS CONTRIBUTED TO RELATIVE STABILIZATION COMPARED TO AREAS TO OUR W AND S WHERE LIFTED INDEX VALUES ARE NOW RUNNING AOB -10. BASED ON THIS...BELIEVE DYNAMIC FORCING WILL BE REQUIRED TO GENERATE CONVECTION. VIGOROUS, DIGGING S/W TROF NOW ROTG SSEWD ACROSS WRN ONTARIO WITH VORT TAIL ARCING SWWD INTO ND ATTM BASED ON AFTN SATLT LOOPS. EXPECT THIS TO TRIGGER MORE ORGANIZED CONVECTION NXT FEW HRS WELL TO OUR NW WITH THESE STORMS MAINTAINING THEMSELVES OVERNIGHT DUE TO MORE FAVORABLE DYNAMICS. AS A RESULT WILL KEEP LIKELY POPS GOING IN FCST BUT WILL MENTION THIS AS AN OVERNIGHT EVENT. THIS IS ALSO SUPPORTED BY MOS AND ALL MODELS CONCUR IN BRINGING OMEGA MAX ACROSS FA OVERNIGHT. SOME PRECIP WILL LIKELY LINGER INTO MONDAY MORNING. REMAINDER OF FCST CHANGED LTL FROM GUID WITH ETA AND GFS IN FAIRLY GOOD AGREEMENT ON STRENGTH OF COLD AVDECTION THRU ERLY PART OF UPCOMING WEEK. WILL KEEP MOSTLY CLOUDY CONDS AT LEAST THRU MONDAY DUE TO SHARP CYCLONINC TURNING IN MID/UPR LVL FLOW AND ASSD COLD ADVECTION. SKIES SHOULD CLEAR TUES NIGHT AS H5 TROF AXIS SHIFTS EWD AND SFC HI PRES BUILDS SEWD INTO FA. .CHI...NONE MERZLOCK
Hazardous weather outlook, Jul 20, 4:20 PM CDT, 1 hour 37 minutes before
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</html>The office that day
Everything else NWS Chicago, IL issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 5:06 PM CDT | Severe Thunderstorm Warning | LOT | Lee | 54 min |
| Jul 20, 5:45 PM CDT | Special Marine Warning | LOT | 90 min | |
| Jul 20, 5:45 PM CDT | Special Marine Warning | LOT | 90 min | |
| Jul 20, 5:45 PM CDT | Special Marine Warning | LOT | 90 min | |
| Jul 20, 6:01 PM CDT | Severe Thunderstorm Warning | LOT | Cook | 19 min |
Nearby
Severe Thunderstorm Warnings in Illinois, 2003Every severe thunderstorm warning in 2003
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.