Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1425
The Storm Prediction Center issued this mesoscale discussion at Aug 6, 2021, 3:23 PM CDT for 4 states. It was in force for 97 min.
The area
The outline as issued.
The facts
- Issued
- Aug 6, 2021, 3:23 PM CDT (20:23 UTC)
- Expired
- Aug 6, 2021, 5:00 PM CDT
- In force
- 97 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 62 counties
Boone County, IL, Champaign County, IL, Cook County, IL, DeKalb County, IL, DeWitt County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Marshall County, IL, McHenry County, IL, McLean County, IL, Ogle County, IL, Putnam County, IL, Tazewell County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL, Benton County, IN, Elkhart County, IN, Jasper County, IN, Lake County, IN, LaPorte County, IN, Marshall County, IN, Newton County, IN, Porter County, IN, Pulaski County, IN, Saint Joseph County, IN, Starke County, IN, White County, IN, Allegan County, MI, Barry County, MI, Berrien County, MI, Cass County, MI, Kalamazoo County, MI, Kent County, MI, Muskegon County, MI, Oceana County, MI, Ottawa County, MI, Saint Joseph County, MI, Van Buren County, MI, Dane County, WI, Dodge County, WI, Fond du Lac County, WI, Jefferson County, WI, Kenosha County, WI, Milwaukee County, WI, Ozaukee County, WI, Racine County, WI, Rock County, WI, Sheboygan County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI
The radar
The Chicago radar (KLOT), 39 km from the middle of the area, began a volume at 20:26 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, 8.4 hours before the alert went out and 204 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
- 516 J/kg
- Mixed-layer CIN
- -90 J/kg
- Mixed-layer LCL
- 1007 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 66 m²/s²
- 0-3 km storm-relative helicity
- 85 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
530
ACUS11 KWNS 062024
SWOMCD
SPC MCD 062023
MIZ000-INZ000-WIZ000-ILZ000-062200-
Mesoscale Discussion 1425
NWS Storm Prediction Center Norman OK
0323 PM CDT Fri Aug 06 2021
Areas affected...Northern Illinois...northern Indiana...southwest
Michigan...and southeast Wisconsin.
Concerning...Severe potential...Watch unlikely
Valid 062023Z - 062200Z
Probability of Watch Issuance...5 percent
SUMMARY...Isolated severe storms are expected through the evening
with a threat for isolated large hail and damaging winds.
DISCUSSION...Isolated thunderstorm activity has occurred through the
morning and early afternoon with very little organization. Strongest
storms have developed across southern Michigan, but these storms are
quickly moving toward a more stable airmass and therefore, are not
expected to be that strong. Greater instability exists farther west
from southern Wisconsin to northern Illinois with MLCAPE of 2000
J/kg per SPC mesoanalysis. Some more rigorous updraft development
and more frequent lightning has recently been observed in eastern
Wisconsin and northern Illinois. Additional storms are possible in
the next few hours, but weak forcing should keep storm coverage
isolated. In addition, shear is quite weak with around 15 to 20
knots per KLOT VWP. Therefore, expect updrafts to be transient with
storm organization less likely. A few stronger updrafts may be
capable of isolated severe hail or a downburst capable of wind
damage, but a greater severe weather threat appears unlikely.
Therefore, no watch is anticipated.
..Bentley/Thompson.. 08/06/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...GRB...LOT...ILX...MKX...DVN...
LAT...LON 40458991 41428932 42168956 43148945 43718888 44078776
44108704 43808619 43308539 42648504 42008515 41428565
40758684 40478767 40128815 39958909 39998946 40458991Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Wisconsin, 2021Mesoscale Discussions in Indiana, 2021Every mesoscale discussion 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.