Alert archive / Iowa / Mesoscale Discussions in 2011

Mesoscale Discussion 241

March 20, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Mar 20, 2011, 2:51 PM CDT for 4 states. It was in force for 114 min.

The area

The outline as issued.

The facts

Issued: Mar 20, 2011, 2:51 PM CDT (19:51 UTC)
Expired: Mar 20, 2011, 4:45 PM CDT
In force: 114 min
Issued by: the Storm Prediction Center

All 69 counties

Adams County, IA, Appanoose County, IA, Benton County, IA, Clarke County, IA, Dallas County, IA, Davis County, IA, Decatur County, IA, Grundy County, IA, Hardin County, IA, Iowa County, IA, Jasper County, IA, Jefferson County, IA, Johnson County, IA, Keokuk County, IA, Linn County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Polk County, IA, Poweshiek County, IA, Ringgold County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Wapello County, IA, Warren County, IA, Washington County, IA, Wayne County, IA, Atchison County, KS, Brown County, KS, Dickinson County, KS, Doniphan County, KS, Douglas County, KS, Geary County, KS, Jackson County, KS, Jefferson County, KS, Johnson County, KS, Leavenworth County, KS, Nemaha County, KS, Pottawatomie County, KS, Riley County, KS, Shawnee County, KS, Wabaunsee County, KS, Wyandotte County, KS, Andrew County, MO, Atchison County, MO, Buchanan County, MO, Caldwell County, MO, Clay County, MO, Clinton County, MO, Daviess County, MO, DeKalb County, MO, Gentry County, MO, Grundy County, MO, Harrison County, MO, Holt County, MO, Livingston County, MO, Mercer County, MO, Nodaway County, MO, Platte County, MO, Putnam County, MO, Schuyler County, MO, Sullivan County, MO, Worth County, MO, Richardson County, NE

The radar

The Des Moines radar (KDMX), 123 km from the middle of the area, began a volume at 19:54 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 12:00Z, 7.9 hours before the alert went out and 199 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: 5 J/kg
Mixed-layer CIN: -751 J/kg
Mixed-layer LCL: 548 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 641 m²/s²
0-3 km storm-relative helicity: 738 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 8.4

Open this sounding in Storm Lab

The text

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

545 
ACUS11 KWNS 201952
SWOMCD
SPC MCD 201951
IAZ000-MOZ000-KSZ000-NEZ000-202145-

MESOSCALE DISCUSSION 0241
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT SUN MAR 20 2011

AREAS AFFECTED...PORTIONS ERN/SRN IA...NWRN AND EXTREME N-CENTRAL
MO...EXTREME SERN NEB...NERN KS.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 201951Z - 202145Z

POTENTIAL INCREASING FOR SVR TSTM DEVELOPMENT INVOF TRIPLE POINT AND
COLD FRONT DESCRIBED BELOW...AND PERHAPS MORE DISCRETE DEVELOPMENT
OVER WARM SECTOR.

19Z SFC ANALYSIS SHOWED TRIPLE POINT OVER CENTRAL IA JUST NW
DSM...WITH COLD FRONT SWWD NEAR BIE-RSL LINE.  WARM FRONT WAS DRAWN
ACROSS DSM AREA SEWD PAST BRL...MORE DIFFUSE AND PERHAPS
DOUBLE-STRUCTURED ACROSS SERN IA AND NWRN IL.  SECONDARY WARM
FRONTAL ZONE WAS EVIDENT WITHIN 20-30 NM S OF I-80...WHERE
DIFFERENTIAL HEATING HAS OCCURRED INVOF SRN FRINGE OF EARLIER
CLOUD/PRECIP REGIME.  THROUGH LATE AFTERNOON...PRIND WARM FRONT WILL
CONTINUE TO MOVE NEWD OVER I-80 CORRIDOR AND SHARPEN/CONSOLIDATE
OVER ERN IA...WHILE COLD FRONT MOVES SEWD ACROSS SWRN/S-CENTRAL
IA...REMAINDER SERN NEB...AND INTO NWRN MO AND NERN KS.

VIS IMAGERY INDICATES VIGOROUS WARM-SECTOR DESTABILIZATION OCCURRING
FROM S-N...CHARACTERIZED BY TRANSITION FROM THICK STRATOCU OVER SWRN
IA TO LARGE-WAVELENGTH BILLOWS NEAR IA/MO BORDER.  CU AND HORIZONTAL
ROLLS HAVE BECOME EVIDENT OVER PORTIONS ERN KS WNW-SSW OF MKC AND
OVER IA/MO BORDER NEAR I-35...INVOF SFC MOIST AXIS.  ADDITIONAL
HEATING/DESTABILIZATION WILL RESULT IN WEAKENING CINH AND
STRENGTHENING BUOYANCY.  MODIFIED RUC SOUNDINGS SUGGEST MLCAPE
RISING TO 1500-2000 J/KG RANGE ACROSS NWRN MO AND NERN KS...AND
1000-1500 J/KG OVER MUCH OF SRN IA PRIOR TO COLD FROPA.  WLY
COMPONENT OF SFC WINDS S OF WARM FRONT WILL LIMIT LOW-LEVEL
HODOGRAPH SIZE...THOUGH FAVORABLE 40-50 KT EFFECTIVE SHEAR MAGNITUDE
IS FCST.  STRONGEST SRH...TOTAL SHEAR AND BOUNDARY-LAYER VORTICITY
IN SUPPORT OF SUPERCELLS WILL DEVELOP INVOF WARM FRONT...WHERE SFC
WINDS ARE RELATIVELY BACKED.  SWWD EXTENT OF EXTENT OF BACKBUILDING
INVOF COLD FRONT IS UNCERTAIN GIVEN STRENGTHENING CAPPING AND WEAKER
FRONTAL ASCENT EXPECTED WITH SWD EXTENT...BUT SVR THREAT MAY INCLUDE
PORTIONS NERN KS AND MKC AREA LATER THIS AFTERNOON.

..EDWARDS.. 03/20/2011

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

ATTN...WFO...DVN...DMX...EAX...OAX...TOP...ICT...

LAT...LON   40159583 40669515 41969383 42469337 42479094 41219159
            40139284 38809472 38799745 40159583

Nearby

Mesoscale Discussions in Iowa, 2011 Mesoscale Discussions in Missouri, 2011 Mesoscale Discussions in Kansas, 2011 Every mesoscale discussion in 2011

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.