Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 566

April 19, 201213 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Apr 19, 2012, 2:23 PM CDT for 13 counties in Iowa. It was in force for 97 min.

The area

The outline as issued.

The facts

Issued: Apr 19, 2012, 2:23 PM CDT (19:23 UTC)
Expired: Apr 19, 2012, 4:00 PM CDT
In force: 97 min
Issued by: the Storm Prediction Center

Counties Audubon County, IA, Boone County, IA, Calhoun County, IA, Carroll County, IA, Crawford County, IA, Dallas County, IA, Greene County, IA, Guthrie County, IA, Hamilton County, IA, Harrison County, IA, Shelby County, IA, Story County, IA, Webster County, IA

The radar

The Des Moines radar (KDMX), 85 km from the middle of the area, began a volume at 19:23 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, 7.4 hours before the alert went out and 148 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: 78 J/kg
Mixed-layer CIN: -225 J/kg
Mixed-layer LCL: 607 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 239 m²/s²
0-3 km storm-relative helicity: 267 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.8

Open this sounding in Storm Lab

The text

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

732 
ACUS11 KWNS 191924
SWOMCD
SPC MCD 191923
IAZ000-NEZ000-192100-

MESOSCALE DISCUSSION 0566
NWS STORM PREDICTION CENTER NORMAN OK
0223 PM CDT THU APR 19 2012

AREAS AFFECTED...CNTRL/W-CNTRL IA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 191923Z - 192100Z

SOME INTENSIFICATION OF ONGOING CONVECTION IN FAR ERN NEB MAY OCCUR
INTO W-CNTRL/CNTRL IA THIS AFTERNOON...WHICH MAY POSE AN
ISOLATED/MARGINAL SVR THREAT. THE ISSUANCE OF A WW IS UNLIKELY.

OMAHA NEB WSR-88D DATA INDICATE INTENSIFYING ELEVATED CONVECTION TO
THE N/W OF THE OMAHA AREA. THIS ACTIVITY IS IN ASSOCIATION WITH A
SEGMENT OF THE WARM CONVEYOR BELT THAT WRAPS AROUND THE NWRN
SEMICIRCLE OF AN INCREASINGLY BETTER-DEFINED EXTRATROPICAL CYCLONE
CROSSING THE MIDDLE MISSOURI VALLEY REGION PER WATER VAPOR IMAGERY.
BETWEEN 35 AND 60 KT OF SWLY/WSWLY FLOW WITHIN THE 3-7-KM-AGL LAYER
PER OMAHA NEB AND DES MOINES IA VWP DATA SUGGESTS THAT THIS
CONVECTION WILL QUICKLY MOVE NEWD/ENEWD INTO W-CNTRL/CNTRL IA DURING
THE NEXT FEW HOURS. AS THE LOW-LEVEL STATIC STABILITY DECREASES TO
THE SOUTH OF A STATIONARY FRONT EXTENDING EAST FROM A SFC LOW NEAR
OMAHA OWING TO INSOLATION/DIABATIC HEATING WITHIN THE DRY-SLOT
CORRIDOR OF THE CYCLONE...THE AFOREMENTIONED CONVECTION WILL LIKELY
ENCOUNTER INCREASING ELEVATED INSTABILITY NORTH OF THE STATIONARY
FRONT AS THE LESS-STATICALLY-STABLE AIR IS ADVECTED ATOP THE
NEAR-SFC COLD DOME. ADDITIONAL CONVECTION MAY ALSO DEVELOP NORTH OF
THE STATIONARY FRONT AS PARCELS ORIGINATING FROM THE WARM SECTOR
REACH THEIR LFC/S NORTH OF THE BOUNDARY. THE PRIMARY CONCERN WITH
ALL OF THIS ACTIVITY WILL BE HAIL...PERHAPS APPROACHING MARGINALLY
SVR THRESHOLDS GIVEN SUFFICIENTLY STRONG DEEP-LAYER SHEAR AND MUCAPE
NORTH OF THE BOUNDARY. HOWEVER...IF ANY STORMS ATTAIN MID-LEVEL
MESOCYCLONES AND EXHIBIT DEVIANT MOTION TO THE RIGHT OF THE MEAN
FLOW...THEY MAY INTERACT WITH THE SFC BOUNDARY/LOW WHILE INGESTING
SFC-BASED INFLOW...IN WHICH CASE A THREAT FOR A WEAK/BRIEF TORNADO
CANNOT BE RULED OUT PROVIDED THE LOW-LEVEL HODOGRAPH CURVATURE PER
DES MOINES IA VWP DATA AND BACKGROUND VERTICAL VORTICITY NEAR THE
FRONT/LOW.

..COHEN.. 04/19/2012

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

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

LAT...LON   41569503 41319565 41519606 41839609 42209582 42529447
            42429331 41929302 41809344 41649421 41569503

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.