Alert archive / Illinois / Mesoscale Discussions in 2011
Mesoscale Discussion 159
The Storm Prediction Center issued this mesoscale discussion at Feb 27, 2011, 8:49 PM CST for 16 counties in Illinois; 4 counties in Wisconsin. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 27, 2011, 8:49 PM CST (02:49 UTC)
- Expired
- Feb 28, 2011, 2:45 AM CST
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
Counties Boone County, IL, Bureau County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Kenosha County, WI, Racine County, WI, Rock County, WI, Walworth County, WI
The radar
The Chicago radar (KLOT), 78 km from the middle of the area, began a volume at 02:50 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
Davenport, (KDVN), launched 00:00Z, 2.8 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 485 m above ground
- 0-6 km bulk shear
- 86 kt
- 0-1 km storm-relative helicity
- 101 m²/s²
- 0-3 km storm-relative helicity
- 136 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
111
ACUS11 KWNS 280249
SWOMCD
SPC MCD 280249
ILZ000-WIZ000-280845-
MESOSCALE DISCUSSION 0159
NWS STORM PREDICTION CENTER NORMAN OK
0849 PM CST SUN FEB 27 2011
AREAS AFFECTED...NRN IL...FAR SERN WI
CONCERNING...WINTER MIXED PRECIPITATION
VALID 280249Z - 280845Z
A WINTRY MIX OF PRECIP WILL SPREAD NEWD ACROSS NRN IL AND FAR SERN
WI /INCLUDING THE CHICAGO AREA/ THIS EVENING INTO TONIGHT. FREEZING
RAIN IS EXPECTED TO OCCUR...WITH RATES AOA 0.05 INCH PER HOUR
POSSIBLE.
INCREASING LOW/MID-LEVEL FRONTOGENESIS ASSOCIATED WITH A SHORTWAVE
TROUGH WILL SPREAD NEWD ACROSS CNTRL/NRN IL AND SRN WI TONIGHT. THIS
WILL SUPPORT THE CONTINUED NEWD MOTION OF A SHIELD OF STRATIFORM
PRECIPITATION...WITH EMBEDDED CONVECTIVE ELEMENTS...INTO THE
DISCUSSION AREA. OBJECTIVE ANALYSIS AROUND 02Z DEPICTS THE SFC
FREEZING LINE EXTENDING FROM NEAR ORD TO NEAR MLI...WHICH IS
EXPECTED TO BE NUDGED SWD THIS EVENING DUE TO COLD AIR ADVECTION.
FREEZING RAIN IS ANTICIPATED TO THE NORTH OF THIS LINE...WITH
FREEZING RAIN REACHING THE CHICAGO AREA AFTER 04Z. ACROSS PORTIONS
OF SERN WI...FORECAST SOUNDINGS DEPICT RELATIVELY COOLER
TEMPERATURES IN THE LOWER TROPOSPHERE...WHICH MAY ALLOW SNOW OR
SLEET TO OCCUR. FREEZING RAIN RATES AOA 0.05 INCH PER HOUR WILL BE
POSSIBLE...ESPECIALLY WITHIN 30 MILES EITHER SIDE OF A LINE FROM
NEAR SQI TO ORD...AS ELEVATED INSTABILITY / 886 J/KG OF MUCAPE PER
00Z ILX SOUNDING / SPREADS NWD AND SUPPORTS UPRIGHT CONVECTION ALONG
WITH THUNDERSTORM ACTIVITY. THIS HAS BEEN AFFIRMED BY THE 0153Z
SURFACE OBSERVATION AT BRL INDICATING A THUNDERSTORM HAVING OCCURRED
IN ASSOCIATION WITH FREEZING RAIN. MOST OF THE PRECIPITATION IS
EXPECTED TO HAVE MOVED EAST OF THE AREA BY 10Z.
..COHEN.. 02/28/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...MKX...DVN...
LAT...LON 41679016 42378995 42768912 42968794 42508734 41908734
41468797 41238907 41278978 41679016SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 27, 8:25 PM CST | Mesoscale Discussion | SPC | Alexander, Bond, Christian, Clark, Clay, Clinton and 39 more | 65 min |
| Feb 27, 9:40 PM CST | Tornado Watch | SPC | Alexander, Bond, Calhoun, Clinton, Edwards, Fayette and 27 more | 6 hr |
| Feb 27, 10:41 PM CST | Mesoscale Discussion | SPC | Bond, Clinton, Franklin, Jackson, Jefferson, Jersey and 9 more | 94 min |
| Feb 27, 11:46 PM CST | Tornado Watch | SPC | Clark, Clay, Crawford, Cumberland, Effingham, Jasper and 2 more | 5 hr |
| Feb 28, 1:05 AM CST | Mesoscale Discussion | SPC | Alexander, Gallatin, Hardin, Massac, Pope, Pulaski | 25 min |
Nearby
Mesoscale Discussions in Illinois, 2011Mesoscale Discussions in Wisconsin, 2011Every mesoscale discussion 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.