Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 385

March 29, 201218 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Mar 29, 2012, 7:55 PM CDT for 18 counties in Iowa. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued: Mar 29, 2012, 7:55 PM CDT (00:55 UTC)
Expired: Mar 29, 2012, 9:00 PM CDT
In force: 65 min
Issued by: the Storm Prediction Center

Counties Adair County, IA, Adams County, IA, Appanoose County, IA, Cass County, IA, Clarke County, IA, Dallas County, IA, Decatur County, IA, Guthrie County, IA, Lucas County, IA, Madison County, IA, Marion County, IA, Monroe County, IA, Polk County, IA, Ringgold County, IA, Taylor County, IA, Union County, IA, Warren County, IA, Wayne County, IA

The radar

The Des Moines radar (KDMX), 76 km from the middle of the area, began a volume at 00:56 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 watches that followed

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

Severe Thunderstorm Watch 117Mar 29, 8:30 PM CDT

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 0.9 hours before the alert went out and 194 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: 761 J/kg
Mixed-layer CIN: -64 J/kg
Mixed-layer LCL: 647 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 76 m²/s²
0-3 km storm-relative helicity: 99 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.5

Open this sounding in Storm Lab

The text

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

837 
ACUS11 KWNS 300055
SWOMCD
SPC MCD 300055 
IAZ000-300200-

MESOSCALE DISCUSSION 0385
NWS STORM PREDICTION CENTER NORMAN OK
0755 PM CDT THU MAR 29 2012

AREAS AFFECTED...PARTS OF CENTRAL AND SRN IA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 300055Z - 300200Z

A SEVERE TSTM WATCH IS BEING CONSIDERED FOR PARTS OF CENTRAL AND SRN
IA /E AND NE OF WW 115/.

EARLY EVENING WATER VAPOR IMAGERY SHOWED THE SRN EXTENT OF A
MID-UPPER LEVEL TROUGH MOVING EWD THROUGH CENTRAL NEB.  ASCENT
ATTENDANT TO THIS SYSTEM WILL CONTINUE SPREAD EWD THROUGH ERN NEB
INTO IA/NRN MO THIS EVENING...WITH THE TROUGH AXIS REACHING THE
NEB/IA BORDER BY 06Z.  THIS ASCENT COMBINED WITH LOW LEVEL WAA
WITHIN THE NOSE OF A 30-40 KT SSWLY LLJ EXTENDING INTO SWRN IA AT
THIS TIME WILL PERSIST THROUGH THE EVENING/OVERNIGHT...AS THE LLJ
VEERS/SHIFTS EWD INTO CENTRAL MO TO ERN IA/NWRN IL BY 09Z.

IA REMAINS N OF A WARM FRONT...WHICH AT 00Z EXTENDED FROM FAR SERN
NEB SEWD INTO FAR SRN IL.  OBJECTIVE ANALYSES INDICATED A STABLE
BOUNDARY LAYER RESIDES N OF THIS FRONT PER LARGER VALUES OF SURFACE
BASED INHIBITION.  HOWEVER...THE AFOREMENTIONED ASCENT COMBINED WITH
ELEVATED INSTABILITY BEING FED INTO SRN/CENTRAL IA BY THE LLJ AND
EFFECTIVE BULK SHEAR AROUND 40 KT WILL SUPPORT ORGANIZED STORMS. 
ELEVATED NATURE OF THIS ACTIVITY WILL TEND TO FAVOR ISOLATED HAIL
AND DAMAGING WINDS AS THE PRIMARY THREATS.

..PETERS.. 03/30/2012

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

ATTN...WFO...DMX...OAX...

LAT...LON   40629464 40699491 41199499 41519503 41619494 41819377
            41379268 40999249 40629262 40629464

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 29, 8:30 PM CDT	Severe Thunderstorm Watch	SPC	Adair, Adams, Appanoose, Cass, Clarke, Decatur and 9 more	6 hr
Mar 29, 9:51 PM CDT	Mesoscale Discussion	SPC	Fremont, Mills, Montgomery, Page	54 min
Mar 29, 11:50 PM CDT	Mesoscale Discussion	SPC	Appanoose, Clarke, Decatur, Lucas, Madison, Mahaska and 6 more	55 min
Mar 30, 3:20 PM CDT	Mesoscale Discussion	SPC	Adams, Audubon, Cass, Crawford, Fremont, Harrison and 7 more	85 min

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.