Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 845

May 19, 201226 counties in Iowa; 7 counties in Minnesota; 4 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at May 19, 2012, 10:33 PM CDT for 26 counties in Iowa; 7 counties in Minnesota; 4 counties in Nebraska. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued
May 19, 2012, 10:33 PM CDT (03:33 UTC)
Expired
May 19, 2012, 11:30 PM CDT
In force
57 min
Issued by
the Storm Prediction Center
All 37 counties

Audubon County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cherokee County, IA, Clay County, IA, Crawford County, IA, Dickinson County, IA, Emmet County, IA, Fremont County, IA, Greene County, IA, Guthrie County, IA, Harrison County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, Palo Alto County, IA, Pocahontas County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Webster County, IA, Blue Earth County, MN, Brown County, MN, Cottonwood County, MN, Faribault County, MN, Jackson County, MN, Martin County, MN, Watonwan County, MN, Cass County, NE, Douglas County, NE, Sarpy County, NE, Washington County, NE

The radar

The Des Moines radar (KDMX), 153 km from the middle of the area, began a volume at 03:35 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

Omaha, NE (KOAX), launched 00:00Z, 3.6 hours before the alert went out and 191 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, Omaha, NE at 00:00Z on 2012-05-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1597 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Omaha, NE at 00:00Z on 2012-05-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 122 square meters per square second.193958Sfc1 km3 km6 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
1597 J/kg
Mixed-layer CIN
-7 J/kg
Mixed-layer LCL
1383 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
122 m²/s²
0-3 km storm-relative helicity
188 m²/s²
Significant tornado parameter
0.8
Supercell composite
8.3

Open this sounding in Storm Lab

The text

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

241 
ACUS11 KWNS 200333
SWOMCD
SPC MCD 200333 
MNZ000-IAZ000-NEZ000-200430-

MESOSCALE DISCUSSION 0845
NWS STORM PREDICTION CENTER NORMAN OK
1033 PM CDT SAT MAY 19 2012

AREAS AFFECTED...WRN IA...SWRN/S-CNTRL MN

CONCERNING...SEVERE THUNDERSTORM WATCH 283...

VALID 200333Z - 200430Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 283
CONTINUES.

SUMMARY...SEVERE THREAT APPEARS TO BE WANING IN MOST OF WW 283 AND
PORTIONS OF THE WW CAN BE CLEARED PRIOR TO 07Z WW EXPIRATION.
DOWNSTREAM WW ISSUANCE INTO MN IS NOT ANTICIPATED ATTM.

DISCUSSION...REMNANT MCV CIRCULATION THAT WAS PART OF AN EARLIER
BOWING MCS HAS NOW REACHED THE NWRN IA/SWRN MN BORDER. REFLECTIVITY
STRUCTURE WITH THIS FEATURE HAS WEAKENED AS IT PROGRESSES INTO AN
INCREASINGLY STABLE AIR MASS WITH NRN EXTENT. WITH CONVECTIVE
OUTFLOW NOW HAVING REACHED A FOD TO SDA LINE AS OF 03Z...AND
LINGERING CONVECTION LIKELY TO REMAIN LARGELY W OF THIS
OUTFLOW...THREAT FOR ADDITIONAL DAMAGING WINDS SHOULD BE LOW. STILL
WITH STRONG SPEED SHEAR ABOVE THE SURFACE-BASED COLD DOME
/INCREASING TO AROUND 50 KT AT 3 KM AGL IN OAX VWP
DATA/...MARGINALLY SEVERE HAIL CANNOT BE COMPLETELY RULED OUT.

..GRAMS.. 05/20/2012

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

ATTN...WFO...MPX...DMX...FSD...OAX...

LAT...LON   44269475 44249414 43869370 42879380 41429444 40899500
            40629565 40739613 41589627 42499598 42999534 43719518
            44079522 44269475

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 19, 8:11 PM CDTMesoscale DiscussionSPCAudubon, Buena Vista, Calhoun, Carroll, Cass, Cherokee and 13 more64 min
May 19, 9:18 PM CDTMesoscale DiscussionSPCMills, Pottawattamie57 min

Nearby

Mesoscale Discussions in Iowa, 2012Mesoscale Discussions in Minnesota, 2012Mesoscale Discussions in Nebraska, 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.