Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 47
The Storm Prediction Center issued this mesoscale discussion at Jan 30, 2021, 6:23 PM CST for 13 counties in Illinois; 6 counties in Indiana. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 30, 2021, 6:23 PM CST (00:23 UTC)
- Expired
- Jan 30, 2021, 10:30 PM CST
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Heavy snow
Counties Bureau County, IL, Carroll County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, Putnam County, IL, Whiteside County, IL, Will County, IL, Jasper County, IN, Lake County, IN, LaPorte County, IN, Newton County, IN, Porter County, IN, Starke County, IN
The radar
The Chicago radar (KLOT), 49 km from the middle of the area, began a volume at 00:27 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 00:00Z, 0.4 hours before the alert went out and 140 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
- 3 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 436 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 458 m²/s²
- 0-3 km storm-relative helicity
- 487 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
579
ACUS11 KWNS 310023
SWOMCD
SPC MCD 310023
MIZ000-INZ000-ILZ000-IAZ000-310430-
Mesoscale Discussion 0047
NWS Storm Prediction Center Norman OK
0623 PM CST Sat Jan 30 2021
Areas affected...far eastern IA...northern IL...northwest IN
Concerning...Heavy snow
Valid 310023Z - 310430Z
SUMMARY...Heavy snowfall will gradually develop this evening with
rates generally in the 1.0-1.5 inches per hour range. Localized
heavier bursts briefly exceeding 1.5 inches per hour are possible.
DISCUSSION...Radar mosaic early this evening shows a broad
precipitation shield across the middle MS Valley spreading
northeastward into the southern Great Lakes. Water-vapor imagery
shows a potent mid-level shortwave trough migrating east-northeast
from the Ozarks and this feature will reach east-central IL by
midnight.
Strong isentropic lift is contributing to increasing precipitation
rates across central IL early this evening. As this zone of ascent
strengthens during the next 1-2 hours and heavier precipitation
moves northeast from central IL, the onset of heavier snowfall rates
will likely occur from near the MS River east into the south and
west suburbs of Chicago. Initially, a mixed precipitation type may
occur on the southern fringe of the MCD area (south of Chicago)
before changing to all snow later this evening. By mid evening,
model guidance indicates the heaviest snow will extend from northern
IL east into northwest IN. The heaviest rates (1.0-1.5 inches per
hour) will probably overspread Chicago and south suburbia during the
8pm-12am CST period.
..Smith.. 01/31/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...LOT...ILX...DVN...
LAT...LON 40928868 40818701 41378651 41788669 42119020 41869056
41479050 40928868SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 30, 9:39 PM CST | Mesoscale Discussion | SPC | Adams, Allen, Blackford, Boone, Carroll, Cass and 30 more | 4 hr |
Nearby
Mesoscale Discussions in Illinois, 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.