Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 718

May 5, 20127 counties in Iowa; Grant County, Wisconsin

The Storm Prediction Center issued this mesoscale discussion at May 5, 2012, 4:56 PM CDT for 7 counties in Iowa; Grant County, Wisconsin. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued
May 5, 2012, 4:56 PM CDT (21:56 UTC)
Expired
May 5, 2012, 6:30 PM CDT
In force
94 min
Issued by
the Storm Prediction Center

Counties Bremer County, IA, Buchanan County, IA, Clayton County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Jackson County, IA, Grant County, WI

The radar

The La Crosse radar (KARX), 120 km from the middle of the area, began a volume at 21:56 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, 9.9 hours before the alert went out and 149 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, Davenport, at 12:00Z on 2012-05-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 25 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, Davenport, at 12:00Z on 2012-05-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 74 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
25 J/kg
Mixed-layer CIN
-344 J/kg
Mixed-layer LCL
780 m above ground
0-6 km bulk shear
34 kt
0-1 km storm-relative helicity
74 m²/s²
0-3 km storm-relative helicity
163 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.0

Open this sounding in Storm Lab

The text

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

773 
ACUS11 KWNS 052157
SWOMCD
SPC MCD 052156
WIZ000-ILZ000-IAZ000-052330-

MESOSCALE DISCUSSION 0718
NWS STORM PREDICTION CENTER NORMAN OK
0456 PM CDT SAT MAY 05 2012

AREAS AFFECTED...PARTS OF NE IA...SWRN WI...NRN IL

CONCERNING...SEVERE THUNDERSTORM WATCH 248...

VALID 052156Z - 052330Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 248
CONTINUES.

SUMMARY...AN INCREASINGLY LOCALIZED SEVERE WEATHER
THREAT...INCLUDING THE RISK FOR LARGE HAIL AND PERHAPS A BRIEF
WINDOW OF OPPORTUNITY FOR DAMAGING WIND GUSTS...MAY CONTINUE ACROSS
PARTS OF NORTHEAST IOWA...SOUTHWEST WISCONSIN...PERHAPS NORTHWESTERN
ILLINOIS THROUGH 00-01Z.  HOWEVER...IT CURRENTLY APPEARS THAT A NEW
WW WILL PROBABLY NOT BE NEEDED.

DISCUSSION...THE ONGOING MESOSCALE CONVECTIVE SYSTEM HAS GENERALLY
UNDERGONE WEAKENING TRENDS AS IT MOVES EASTWARD INTO A PROGRESSIVELY
DEEPER NEAR SURFACE COOL/STABLE LAYER ACROSS WESTERN WISCONSIN.
HOWEVER...LOWER/MID TROPOSPHERIC WARM ADVECTION IS MAINTAINING
STRONG/SEVERE STORM DEVELOPMENT ON THE SOUTHERN FLANK OF THE
SYSTEM...IN CLOSER PROXIMITY TO THE FRONT...WHERE INHIBITION HAS YET
TO STRENGTHEN SUFFICIENTLY TO CAP RENEWED DEVELOPMENT.  IT APPEARS
POSSIBLE THAT THIS MAY CONTINUE AT LEAST ANOTHER FEW HOURS ACROSS
PARTS OF NORTHEAST IOWA/SOUTHWEST WISCONSIN...PERHAPS NORTHWESTERN
ILLINOIS...WHERE A RISK FOR LARGE HAIL MAY PERSIST...ALONG WITH
PERHAPS A SHORT-LIVED RISK FOR STRONG SURFACE GUSTS.
HOWEVER...MODELS DO INDICATE THAT WEAKENING LOW-LEVEL WARM
ADVECTION...COUPLED WITH STRENGTHENING MID-LEVEL INHIBITION SHOULD
ACT TO DIMINISH ANY REMAINING CONVECTIVE POTENTIAL BY THE 00-01Z
TIME FRAME...IF NOT BEFORE.

..KERR.. 05/05/2012

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

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

LAT...LON   43189207 43049090 42769040 42089039 42399179 42689255
            43189207

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 4, 8:30 PM CDTMesoscale DiscussionSPCAllamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 10 more60 min
May 4, 9:54 PM CDTMesoscale DiscussionSPCBuena Vista, Cherokee, Crawford, Harrison, Ida, Monona and 5 more96 min
May 5, 6:49 AM CDTSevere Thunderstorm WatchSPCCherokee, Lyon, O'Brien, Osceola, Plymouth, Sioux7 hr
May 5, 11:38 AM CDTSevere Thunderstorm WatchSPCAllamakee, Cerro Gordo, Chickasaw, Clayton, Emmet, Fayette and 8 more6 hr
May 5, 2:09 PM CDTMesoscale DiscussionSPCBuena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more96 min
May 5, 2:58 PM CDTMesoscale DiscussionSPCAllamakee, Dickinson, Emmet, Howard, Kossuth, Mitchell and 3 more62 min
May 5, 3:52 PM CDTMesoscale DiscussionSPCBuena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more83 min
May 5, 5:31 PM CDTTornado WatchSPCPlymouth, Sioux, Woodbury5 hr
May 5, 6:46 PM CDTSevere Thunderstorm WatchSPCLyon6 hr

Nearby

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