Alert archive / Illinois / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 63

March 27, 202119 counties in Illinois; 4 counties in Missouri

The Storm Prediction Center issued this severe thunderstorm watch at Mar 27, 2021, 8:19 PM CDT for 19 counties in Illinois; 4 counties in Missouri. It was in force for 114 min.

The area

The outline as issued.

The facts

Issued: Mar 27, 2021, 8:19 PM CDT (01:19 UTC)
Expired: Mar 27, 2021, 10:13 PM CDT
In force: 114 min
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 55 kt

All 23 counties

Clay County, IL, Crawford County, IL, Edwards County, IL, Franklin County, IL, Gallatin County, IL, Hamilton County, IL, Jackson County, IL, Jasper County, IL, Jefferson County, IL, Johnson County, IL, Lawrence County, IL, Perry County, IL, Richland County, IL, Saline County, IL, Union County, IL, Wabash County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Bollinger County, MO, Cape Girardeau County, MO, Perry County, MO, Wayne County, MO

The radar

The Evansville,IN radar (KVWX), 75 km from the middle of the area, began a volume at 01:22 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: 20%
One or more EF2 to EF5 tornadoes: 5%
Ten or more severe wind reports: 40%
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

5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Mar 27, 8:20 PM CDT	Severe Thunderstorm Warning	ILX	Clay, Effingham, Jasper	55 min
Mar 27, 8:22 PM CDT	Severe Thunderstorm Warning	PAH	Perry	38 min
Mar 27, 8:43 PM CDT	Severe Thunderstorm Warning	PAH	Bollinger, Cape Girardeau, Perry	24 min
Mar 27, 9:02 PM CDT	Severe Thunderstorm Warning	ILX	Clay, Crawford, Jasper, Lawrence, Richland	58 min
Mar 27, 9:11 PM CDT	Severe Thunderstorm Warning	PAH	Wayne	49 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 00:00Z, 1.3 hours before the alert went out and 206 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 933 m above ground
0-6 km bulk shear: 86 kt
0-1 km storm-relative helicity: -3 m²/s²
0-3 km storm-relative helicity: 202 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

271 
WWUS20 KWNS 280115
SEL3  
SPC WW 280115
ILZ000-MOZ000-280400-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 63
NWS Storm Prediction Center Norman OK
820 PM CDT Sat Mar 27 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Southeast Illinois
  Southeast Missouri

* Effective this Saturday evening from 820 PM until 1100 PM CDT.

* Primary threats include...
  Scattered damaging wind gusts to 65 mph possible
  A tornado or two possible

SUMMARY...A QLCS will spread east across southeast Missouri and
southeast Illinois before weakening during the late evening.

The severe thunderstorm watch area is approximately along and 45
statute miles east and west of a line from 55 miles east northeast
of Salem IL to 45 miles southwest of Carbondale IL. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU3).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for 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. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 59...WW 60...WW 61...WW
62...

AVIATION...A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 55 knots. A few
cumulonimbi with maximum tops to 450. Mean storm motion vector
23035.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 27, 7:58 PM CDT	Mesoscale Discussion	SPC	Alexander, Clay, Clinton, Edwards, Effingham, Franklin and 16 more	92 min

Nearby

Severe Thunderstorm Watches in Illinois, 2021 Severe Thunderstorm Watches in Missouri, 2021 Every severe thunderstorm watch in 2021

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.