Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 2129

December 3, 201241 counties in Illinois; 8 counties in Iowa; 16 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Dec 3, 2012, 3:29 PM CST for 41 counties in Illinois; 8 counties in Iowa; 16 counties in Wisconsin. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Dec 3, 2012, 3:29 PM CST (21:29 UTC)
Expired: Dec 3, 2012, 5:00 PM CST
In force: 91 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 65 counties

Cedar County, IA, Clinton County, IA, Des Moines County, IA, Jackson County, IA, Lee County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Adams County, IL, Boone County, IL, Brown County, IL, Bureau County, IL, Carroll County, IL, Cass County, IL, DeKalb County, IL, DuPage County, IL, Fulton County, IL, Grundy County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Marshall County, IL, Mason County, IL, McDonough County, IL, McHenry County, IL, Menard County, IL, Mercer County, IL, Ogle County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Schuyler County, IL, Scott County, IL, Stark County, IL, Stephenson County, IL, Tazewell County, IL, Warren County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL, Calumet County, WI, Columbia County, WI, Dane County, WI, Dodge County, WI, Fond du Lac County, WI, Green County, WI, Green Lake County, WI, Iowa County, WI, Jefferson County, WI, Lafayette County, WI, Marquette County, WI, Rock County, WI, Sauk County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI

The radar

The Quad Cities radar (KDVN), 75 km from the middle of the area, began a volume at 21:32 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 12:00Z, 9.5 hours before the alert went out and 69 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: 763 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 154 m²/s²
0-3 km storm-relative helicity: 146 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.

937 
ACUS11 KWNS 032129
SWOMCD
SPC MCD 032129 
ILZ000-WIZ000-IAZ000-MOZ000-032300-

MESOSCALE DISCUSSION 2129
NWS STORM PREDICTION CENTER NORMAN OK
0329 PM CST MON DEC 03 2012

AREAS AFFECTED...FAR ERN IA...NRN AND W-CNTRL IL...SRN WI

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 032129Z - 032300Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...SCATTERED THUNDERSTORMS ARE FORECAST TO DEVELOP ACROSS FAR
ERN IA...NRN AND W-CNTRL IL...AND SRN WI THIS EVENING. A FEW STORMS
MAY BECOME STRONG TO SEVERE...POSING AN ISOLATED THREAT FOR DAMAGING
WIND GUSTS AND PERHAPS A BRIEF TORNADO.

DISCUSSION...WV IMAGERY AT 21Z SHOWS A VORT LOBE PROGRESSING EWD
INTO THE UPPER MS VALLEY REGION...WHILE AN ASSOCIATED SURFACE COLD
FRONT EXTENDED SWWD FROM NRN WI INTO CNTRL/ERN IA AND NRN MO. A WARM
FRONT WAS ALSO RETREATING NWD INTO CNTRL WI AND LOWER MI. DEWPOINTS
AHEAD OF THE COLD FRONT RESIDE IN THE UPPER 50S...WHILE TEMPERATURES
HAVE WARMED INTO THE 60S TO AROUND 70F. HOWEVER... STRONGER BOUNDARY
LAYER DESTABILIZATION HAS BEEN INHIBITED BY PRE-FRONTAL
STRATOCUMULUS. GIVEN ONLY MODEST SURFACE HEATING AND
MOISTURE...COMBINED WITH RATHER WEAK MIDLEVEL LAPSE RATES...SBCAPE
VALUES ONLY RANGE FROM 500-1000 J/KG.

AS THE COLD FRONT PROGRESSES EWD ACROSS THE AREA THIS
EVENING...SCATTERED THUNDERSTORMS ARE FORECAST TO DEVELOP. A MESSY
CONVECTIVE MODE...CONSISTING MAINLY OF LINE SEGMENTS...MAY UNFOLD
DUE TO WEAK BOUNDARY LAYER DESTABILIZATION AND MODEST 30-40 KT
DEEP-LAYER SHEAR. IN ADDITION...STRONGER DCVA/LARGE-SCALE FORCING
FOR ASCENT IS FORECAST TO BE N OF THE AREA...WHICH COULD OTHERWISE
COMPENSATE SOMEWHAT FOR THE LOW CAPE/MODERATE SHEAR ENVIRONMENT.
THEREFORE...EXPECT ISOLATED STRONG/SEVERE WIND GUSTS TO BE THE
PRIMARY THREAT WITH STORMS TONIGHT. IN ADDITION...A 40-50 KT S-SWLY
LLJ WILL AID IN EFFECTIVE SRH VALUES NEAR 200 M2 S-2. THUS...A BRIEF
TORNADO CANNOT BE RULED OUT.

..GARNER/MEAD.. 12/03/2012

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

ATTN...WFO...GRB...LOT...ILX...MKX...LSX...DVN...ARX...

LAT...LON   41468788 40068942 39609050 39809135 40799162 42609078
            43838958 44198813 41468788

Nearby

Mesoscale Discussions in Illinois, 2012 Mesoscale Discussions in Wisconsin, 2012 Mesoscale Discussions in Iowa, 2012 Every 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.