Alert archive / Illinois / Tornado Watches in 2011
Tornado Watch 37
The Storm Prediction Center issued this tornado watch at Mar 4, 2011, 4:54 PM CST for 22 counties in Illinois; 15 counties in Missouri. It was in force for 118 min.
The area
The outline as issued.
The facts
- Issued
- Mar 4, 2011, 4:54 PM CST (22:54 UTC)
- Expired
- Mar 4, 2011, 6:52 PM CST
- In force
- 118 min
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 37 counties
Bond County, IL, Calhoun County, IL, Christian County, IL, Clay County, IL, Clinton County, IL, Effingham County, IL, Fayette County, IL, Greene County, IL, Jersey County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Pike County, IL, Randolph County, IL, Saint Clair County, IL, Sangamon County, IL, Scott County, IL, Shelby County, IL, Washington County, IL, City of Saint Louis, MO, Crawford County, MO, Franklin County, MO, Iron County, MO, Jefferson County, MO, Lincoln County, MO, Madison County, MO, Pike County, MO, Reynolds County, MO, Saint Charles County, MO, Saint Francois County, MO, Saint Louis County, MO, Sainte Genevieve County, MO, Warren County, MO, Washington County, MO
The radar
The St Louis radar (KLSX), 26 km from the middle of the area, began a volume at 22:54 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 30%
- One or more EF2 to EF5 tornadoes
- 10%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 4, 5:23 PM CST | Severe Thunderstorm Warning | LSX | Calhoun, Jersey, Madison | 29 min |
| Mar 4, 6:20 PM CST | Flash Flood Warning | LSX | Madison, Saint Clair | 5 hr |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Lincoln, IL (KILX), launched 12:00Z, 10.9 hours before the alert went out and 215 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1266 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 213 m²/s²
- 0-3 km storm-relative helicity
- 228 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
269
WWUS20 KWNS 042301
SEL7
SPC WW 042301
ILZ000-MOZ000-050400-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 37
NWS STORM PREDICTION CENTER NORMAN OK
455 PM CST FRI MAR 4 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
WEST CENTRAL ILLINOIS
EAST CENTRAL MISSOURI
EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 455 PM UNTIL
1000 PM CST.
TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 65 STATUTE
MILES EAST AND WEST OF A LINE FROM 65 MILES NORTH NORTHEAST OF
ALTON ILLINOIS TO 45 MILES WEST SOUTHWEST OF FARMINGTON MISSOURI.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU7).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.
OTHER WATCH INFORMATION...CONTINUE...WW 36...
DISCUSSION...ERN MO QLCS WITH EMBEDDED SUPERCELLS EXPECTED TO
CONTINUE MAINLY ENE...WITH SOME SWD DEVELOPMENT POSSIBLE LATER THIS
EVE. COOL MID LVL TEMPS AND MOISTURE AXIS EXTENDING N UP THE MID MS
VLY ARE COMPENSATING FOR RELATIVELY MODEST SFC TEMPS TO YIELD
SUFFICIENT INSTABILITY FOR SUSTAINED SFC-BASED STORMS. AS LOW LVL
WIND FIELD STRENGTHENS THROUGH THE EVE...AND CNTRL MO UPR IMPULSE
CONTINUES ENEWD...POTENTIAL MAY CONTINUE FOR LOW-LVL MESOS WITH A
THREAT FOR ISOLD TORNADOES...IN ADDITION TO SMALL BOWS WITH DMGG
WIND.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 24035.
...CORFIDISPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 4, 1:33 PM CST | Severe Thunderstorm Watch | SPC | Calhoun | 5 hr |
| Mar 4, 3:22 PM CST | Mesoscale Discussion | SPC | Calhoun, Cass, Greene, Jersey, Macoupin, Menard and 4 more | 83 min |
| Mar 4, 11:52 AM CST | Mesoscale Discussion | SPC | Barry, Barton, Benton, Camden, Cedar, Christian and 15 more | 2 hr |
| Mar 4, 3:55 PM CST | Mesoscale Discussion | SPC | Barry, Cedar, Christian, Dade, Dallas, Douglas and 14 more | 95 min |
Nearby
Tornado Watches in Illinois, 2011Tornado Watches in Missouri, 2011Every tornado watch in 2011
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.