Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 1297

June 28, 20127 counties in Illinois; 5 counties in Indiana; 6 counties in Michigan

The Storm Prediction Center issued this mesoscale discussion at Jun 28, 2012, 5:30 PM CDT for 7 counties in Illinois; 5 counties in Indiana; 6 counties in Michigan. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued
Jun 28, 2012, 5:30 PM CDT (22:30 UTC)
Expired
Jun 28, 2012, 7:00 PM CDT
In force
90 min
Issued by
the Storm Prediction Center
Chance of a watch
40%

Counties Cook County, IL, DeKalb County, IL, DuPage County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, Will County, IL, Elkhart County, IN, Lake County, IN, LaPorte County, IN, Porter County, IN, Saint Joseph County, IN, Allegan County, MI, Berrien County, MI, Cass County, MI, Kalamazoo County, MI, Saint Joseph County, MI, Van Buren County, MI

The radar

The Northern Indiana radar (KIWX), 118 km from the middle of the area, began a volume at 22:33 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 10.5 hours before the alert went out and 263 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-pSkew-T log-p diagram, Lincoln, IL at 12:00Z on 2012-06-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 194 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lincoln, IL at 12:00Z on 2012-06-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -5 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
194 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2152 m above ground
0-6 km bulk shear
18 kt
0-1 km storm-relative helicity
-5 m²/s²
0-3 km storm-relative helicity
35 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

123 
ACUS11 KWNS 282230
SWOMCD
SPC MCD 282230 
MIZ000-INZ000-ILZ000-290000-

MESOSCALE DISCUSSION 1297
NWS STORM PREDICTION CENTER NORMAN OK
0530 PM CDT THU JUN 28 2012

AREAS AFFECTED...NERN IL...NRN IND...SWRN LOWER MI

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 282230Z - 290000Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...AN AT LEAST ISOLATED SVR THREAT MAY MATERIALIZE ACROSS
PARTS OF NERN IL/NRN IND/SWRN LOWER MI. CONVECTIVE TRENDS WILL
CONTINUE TO BE MONITORED...AND A WW IS POSSIBLE IF A MORE WIDESPREAD
SVR THREAT APPEARS TO ENSUE.

DISCUSSION...ISOLATED CONVECTION IS DEVELOPING INVOF A SFC FRONT AND
NEARBY WIND-SHIFT AXES...ENHANCED BY LOCALIZED LAKE-BREEZE
CIRCULATIONS NEAR AND NORTH OF THE CHICAGO AREA. THE AREAS OF
GREATEST CONCERN FOR POSSIBLY SVR CONVECTION DURING THE NEXT HOUR OR
TWO INCLUDE KANE COUNTY EWD TO COOK COUNTY INTO SRN LAKE
MICHIGAN...WITH POTENTIAL IMPACTS TO THE CHICAGO AREA BETWEEN 2300
AND 2330 UTC.

THE CONVECTION APPEARS TO BE COLOCATED WITH THE WARM SIDE OF A
700-MB THERMAL GRADIENT. WHILE HOT INLAND SFC TEMPERATURES AMIDST
LOWER/MIDDLE 70S DEWPOINTS ARE SUPPORTING EXTREME
INSTABILITY...STRONG INHIBITION SOUTH OF THE 700-MB TEMPERATURE
GRADIENT OWING TO A PRONOUNCED WARM-LAYER ALOFT -- 700-MB TEMPS IN
EXCESS OF 16C -- YIELD UNCERTAINTY WITH REGARD TO THE FUTURE
EVOLUTION OF ONGOING CONVECTION. FURTHERMORE...THE ONLY GLANCING
INFLUENCE OF A MID-LEVEL SHORTWAVE TROUGH AND ASSOCIATED HEIGHT
FALLS/ASCENT SHOULD PROVIDE ONLY MINIMAL REDUCTION TO ONGOING CINH.

REGARDLESS...THERE IS SOME CONCERN FOR A LOCALIZED SVR-WIND THREAT
GIVEN SFC DEWPOINT DEPRESSIONS IN EXCESS OF 20F AND DCAPE VALUES IN
AOA 1300 J/KG...AS WLY/NWLY MID-LEVEL FLOW STEERS CONVECTION FROM
NERN IL INTO SWRN LOWER MI AND NRN IND. IF STORMS APPEAR TO SHOW
SIGNS OF GROWING UPSCALE INTO A CONVECTIVE COMPLEX WITH A MORE
WIDESPREAD SVR THREAT...A WW MAY BE NEEDED.

..COHEN/HART.. 06/28/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...IWX...GRR...LOT...

LAT...LON   42078508 41738528 41388615 41278783 41658893 42078911
            42318826 42428749 42558686 42688579 42558527 42078508

Nearby

Mesoscale Discussions in Illinois, 2012Mesoscale Discussions in Michigan, 2012Mesoscale Discussions in Indiana, 2012Every mesoscale discussion in 2012

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.