Alert archive / Iowa / Mesoscale Discussions in 2007

Mesoscale Discussion 1663

August 6, 200716 counties in Illinois; 23 counties in Iowa; Lafayette County, Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Aug 6, 2007, 2:22 PM CDT for 16 counties in Illinois; 23 counties in Iowa; Lafayette County, Wisconsin. It was in force for 83 min.

The area

The outline as issued.

The facts

Issued: Aug 6, 2007, 2:22 PM CDT (19:22 UTC)
Expired: Aug 6, 2007, 3:45 PM CDT
In force: 83 min
Issued by: the Storm Prediction Center

All 40 counties

Benton County, IA, Black Hawk County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cedar County, IA, Clayton County, IA, Clinton County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Grundy County, IA, Hardin County, IA, Iowa County, IA, Jackson County, IA, Johnson County, IA, Jones County, IA, Linn County, IA, Marshall County, IA, Muscatine County, IA, Poweshiek County, IA, Scott County, IA, Tama County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, Grundy County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, Ogle County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Lafayette County, WI

The radar

The Quad Cities radar (KDVN), 70 km from the middle of the area, began a volume at 19:24 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, 7.4 hours before the alert went out and 73 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: 2191 J/kg
Mixed-layer CIN: -33 J/kg
Mixed-layer LCL: 738 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 45 m²/s²
0-3 km storm-relative helicity: 17 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 2.6

Open this sounding in Storm Lab

The text

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

000 
ACUS11 KWNS 061922
SWOMCD
SPC MCD 061922 
ILZ000-WIZ000-IAZ000-062045-

MESOSCALE DISCUSSION 1663
NWS STORM PREDICTION CENTER NORMAN OK
0222 PM CDT MON AUG 06 2007

AREAS AFFECTED...IA...PARTS OF SW WI...NRN IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 061922Z - 062045Z

TRENDS CONTINUE TO BE MONITORED FOR AN INCREASING SEVERE THREAT AND
THE POSSIBILITY OF A WW.

WARM MID-LEVEL ENVIRONMENT ACROSS THE MID MISSOURI VALLEY HAS
SUPPRESSED DEEP CONVECTIVE DEVELOPMENT.  BUT...AREA OF STRONGER
FORCING ASSOCIATED WITH WEAK MID-LEVEL IMPULSE CONTINUES EAST
NORTHEASTWARD WITHIN BROADER SCALE ANTICYCLONIC UPPER FLOW INTO THE
MID/UPPER MISSISSIPPI VALLEY.  THIS APPEARS LIKELY TO ENHANCE LIFT
ALONG A RETREATING SURFACE WARM FRONT NORTH OF THE INTERSTATE 80
CORRIDOR...INTO NORTH CENTRAL/NORTHEAST IOWA...PERHAPS NORTHERN
ILLINOIS...BY 21-22Z.  THE LOWER/MID TROPOSPHERE IS NOT QUITE AS
WARM ACROSS THIS REGION...AND THE 18Z SOUNDING FROM DAVENPORT
INDICATES AN UNCAPPED MIXED BOUNDARY LAYER WITH CAPE IN EXCESS OF
3000 J/KG.  A SLOW INCREASE IN CONVECTION IS ONGOING...AND A
GRADUALLY UPSCALE EVOLUTION INTO AN EVOLVING CLUSTER OF STORMS IS
POSSIBLE LATE THIS AFTERNOON.  

WITH WESTERLY 500 MB FLOW PROGGED TO STRENGTHEN FROM 20 TO 30+ KT
LATE THIS AFTERNOON...DEEP LAYER SHEAR MAY BECOME SUFFICIENT FOR
SUPERCELLS...PARTICULARLY IF WEAK SURFACE LOW PERSISTS WEST/
NORTHWEST OF CEDAR RAPIDS.  THIS COULD PROMOTE A FAVORABLE
ENVIRONMENT FOR AN ISOLATED BRIEF TORNADO OR TWO...BEFORE
EVAPORATIVE COOLING ASSOCIATED WITH UNSATURATED MID-LEVEL PROFILES 
CONTRIBUTES TO AN EXPANDING COLD POOL NEAR POSSIBLE GROWING STORM
CLUSTER.  OTHERWISE...PRESENCE OF HIGH PRECIPITABLE WATER CONTENT IN
EXCESS OF 2 INCHES...WILL SUPPORT RISK OF HEAVY RAINFALL IN SLOW
MOVING...TRAINING CONVECTION.

..KERR.. 08/06/2007

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

ATTN...WFO...LOT...MKX...DVN...ARX...DMX...

42499329 42969237 42949107 42789052 42548898 41688802
41238819 41308991 41539153 41539275 41909315

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 5, 7:56 PM CDT	Mesoscale Discussion	SPC	Champaign, DeWitt, Douglas, Edgar, Ford, Iroquois and 7 more	64 min
Aug 5, 11:44 PM CDT	Mesoscale Discussion	SPC	Appanoose, Wayne	91 min
Aug 6, 11:08 AM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Boone, Carroll, Cass and 28 more	97 min

Nearby

Mesoscale Discussions in Iowa, 2007 Mesoscale Discussions in Illinois, 2007 Mesoscale Discussions in Wisconsin, 2007 Every mesoscale discussion in 2007

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.