Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 704

May 4, 201216 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at May 4, 2012, 8:30 PM CDT for 16 counties in Iowa. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: May 4, 2012, 8:30 PM CDT (01:30 UTC)
Expired: May 4, 2012, 9:30 PM CDT
In force: 60 min
Issued by: the Storm Prediction Center

Counties Allamakee County, IA, Benton County, IA, Black Hawk County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cedar County, IA, Chickasaw County, IA, Clayton County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Grundy County, IA, Jones County, IA, Linn County, IA, Winneshiek County, IA

The radar

The La Crosse radar (KARX), 137 km from the middle of the area, began a volume at 01:31 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, 1.5 hours before the alert went out and 145 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: 152 J/kg
Mixed-layer CIN: -60 J/kg
Mixed-layer LCL: 1202 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: -40 m²/s²
0-3 km storm-relative helicity: -2 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.2

Open this sounding in Storm Lab

The text

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

010 
ACUS11 KWNS 050130
SWOMCD
SPC MCD 050130 
ILZ000-IAZ000-WIZ000-050230-

MESOSCALE DISCUSSION 0704
NWS STORM PREDICTION CENTER NORMAN OK
0830 PM CDT FRI MAY 04 2012

AREAS AFFECTED...NERN IA

CONCERNING...SEVERE THUNDERSTORM WATCH 242...

VALID 050130Z - 050230Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 242
CONTINUES.

SUMMARY...SMALL BOW ECHO MOVING EWD AT 30 KT ACROSS FAR NERN IA MAY
POSE A LIMITED THREAT FOR A STRONG WIND GUST OR TWO.  HOWEVER...
OVERALL SEVERE WEATHER THREAT IS EXPECTED TO CONTINUE WANING...WITH
POTENTIAL FOR WW 242 TO BE CANCELLED WELL BEFORE THE SCHEDULED 05Z
EXPIRATION.

DISCUSSION...AT 0125Z...REGIONAL RADAR IMAGERY SHOWED A SMALL BOWING
LINE SEGMENT LOCATED OVER NERN IA /ERN WINNESHIEK COUNTY TO BREMER
COUNTY/.  THIS ACTIVITY HAS SLOWED ITS EWD MOVEMENT TO 30 KT. THIS
SLOWER SPEED COMBINED WITH A STABILIZING BOUNDARY LAYER SUGGESTS THE
OVERALL SEVERE WEATHER THREAT WILL CONTINUE TO WANE AND NOT WARRANT
THE ISSUANCE OF ADDITIONAL DOWNSTREAM WATCHES.

..PETERS.. 05/05/2012

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

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

LAT...LON   41669090 42399294 42909276 43429215 43449162 43109112
            42449054 41669090

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 4, 9:54 PM CDT	Mesoscale Discussion	SPC	Buena Vista, Cherokee, Crawford, Harrison, Ida, Monona and 5 more	96 min
May 5, 6:49 AM CDT	Severe Thunderstorm Watch	SPC	Cherokee, Lyon, O'Brien, Osceola, Plymouth, Sioux	7 hr
May 5, 11:38 AM CDT	Severe Thunderstorm Watch	SPC	Allamakee, Cerro Gordo, Chickasaw, Clayton, Emmet, Fayette and 8 more	6 hr
May 5, 2:09 PM CDT	Mesoscale Discussion	SPC	Buena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more	96 min
May 5, 2:58 PM CDT	Mesoscale Discussion	SPC	Allamakee, Dickinson, Emmet, Howard, Kossuth, Mitchell and 3 more	62 min
May 5, 3:52 PM CDT	Mesoscale Discussion	SPC	Buena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford and 8 more	83 min
May 5, 4:56 PM CDT	Mesoscale Discussion	SPC	Bremer, Buchanan, Clayton, Delaware, Dubuque, Fayette and 1 more	94 min
May 5, 5:31 PM CDT	Tornado Watch	SPC	Plymouth, Sioux, Woodbury	5 hr
May 5, 6:46 PM CDT	Severe Thunderstorm Watch	SPC	Lyon	6 hr

Nearby

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.