Alert archive / Illinois / Severe Thunderstorm Watches in 2015
Severe Thunderstorm Watch 27
The Storm Prediction Center issued this severe thunderstorm watch at Apr 7, 2015, 8:34 AM CDT for 13 counties in Illinois; 6 counties in Missouri. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 7, 2015, 8:34 AM CDT (13:34 UTC)
- Expired
- Apr 7, 2015, 3:29 PM CDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Clinton County, IL, Franklin County, IL, Jackson County, IL, Jefferson County, IL, Johnson County, IL, Madison County, IL, Monroe County, IL, Perry County, IL, Randolph County, IL, Saint Clair County, IL, Union County, IL, Washington County, IL, Williamson County, IL, Cape Girardeau County, MO, City of Saint Louis, MO, Jefferson County, MO, Perry County, MO, Saint Louis County, MO, Sainte Genevieve County, MO
The radar
The St Louis radar (KLSX), 87 km from the middle of the area, began a volume at 13:34 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
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 7, 8:42 AM CDT | Severe Thunderstorm Warning | LSX | Franklin, Jefferson, Saint Charles, Saint Louis | 48 min |
| Apr 7, 9:18 AM CDT | Severe Thunderstorm Warning | LSX | Franklin, Jefferson | 42 min |
| Apr 7, 9:26 AM CDT | Severe Thunderstorm Warning | LSX | Jefferson, Saint Louis, City of Saint Louis | 49 min |
| Apr 7, 9:42 AM CDT | Flash Flood Warning | LSX | Franklin, Jefferson, Saint Charles, Saint Louis, Warren | 8 hr |
| Apr 7, 9:58 AM CDT | Severe Thunderstorm Warning | LSX | Franklin, Jefferson | 47 min |
| Apr 7, 10:03 AM CDT | Severe Thunderstorm Warning | LSX | Monroe, Saint Clair | 42 min |
| Apr 7, 10:53 AM CDT | Flash Flood Warning | LSX | Monroe | 4 hr |
| Apr 7, 12:47 PM CDT | Flash Flood Warning | LSX | Randolph | 6 hr |
| Apr 7, 1:09 PM CDT | Severe Thunderstorm Warning | PAH | Jackson, Perry | 51 min |
| Apr 7, 1:36 PM CDT | Severe Thunderstorm Warning | PAH | Jackson | 39 min |
| Apr 7, 2:15 PM CDT | Severe Thunderstorm Warning | PAH | Jackson, Williamson | 45 min |
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, 1.6 hours before the alert went out and 234 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
- 134 J/kg
- Mixed-layer CIN
- -199 J/kg
- Mixed-layer LCL
- 443 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 23 m²/s²
- 0-3 km storm-relative helicity
- 87 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 7, 8:17 AM CDT | Mesoscale Discussion | SPC | Bond, Clinton, Franklin, Hamilton, Jackson, Jefferson and 11 more | 88 min |
| Apr 7, 10:51 AM CDT | Mesoscale Discussion | SPC | Franklin, Gallatin, Hamilton, Hardin, Jackson, Jefferson and 11 more | 54 min |
| Apr 7, 1:14 PM CDT | Mesoscale Discussion | SPC | Edwards, Franklin, Gallatin, Hamilton, Hardin, Jackson and 7 more | 61 min |
| Apr 7, 1:37 PM CDT | Severe Thunderstorm Watch | SPC | Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 10 more | 5 hr |
| Apr 7, 2:53 PM CDT | Mesoscale Discussion | SPC | Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 14 more | 97 min |
| Apr 7, 3:51 AM CDT | Mesoscale Discussion | SPC | Audrain, Boone, Caldwell, Carroll, Chariton, Daviess and 9 more | 54 min |
| Apr 7, 5:03 PM CDT | Mesoscale Discussion | SPC | Barton, Bates, Cass, Cedar, Dade, Greene and 9 more | 2 hr |
Nearby
Severe Thunderstorm Watches in Illinois, 2015Severe Thunderstorm Watches in Missouri, 2015Every severe thunderstorm watch in 2015
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.