Alert archive / Iowa / Mesoscale Discussions in 2014

Mesoscale Discussion 1513

August 4, 201442 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Aug 4, 2014, 2:06 PM CDT for 42 counties in Iowa. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Aug 4, 2014, 2:06 PM CDT (19:06 UTC)
Expired: Aug 4, 2014, 3:30 PM CDT
In force: 84 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 42 counties

Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cerro Gordo County, IA, Cherokee County, IA, Chickasaw County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Humboldt County, IA, Ida County, IA, Jasper County, IA, Kossuth County, IA, Lyon County, IA, Marshall County, IA, Mitchell County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Plymouth County, IA, Pocahontas County, IA, Sac County, IA, Sioux County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winnebago County, IA, Worth County, IA, Wright County, IA

The radar

The Des Moines radar (KDMX), 114 km from the middle of the area, began a volume at 19:09 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

Minneapolis, MN (KMPX), launched 12:00Z, 7.1 hours before the alert went out and 238 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: 767 J/kg
Mixed-layer CIN: -51 J/kg
Mixed-layer LCL: 1046 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 40 m²/s²
0-3 km storm-relative helicity: 46 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

205 
ACUS11 KWNS 041906
SWOMCD
SPC MCD 041906 
IAZ000-MNZ000-SDZ000-042030-

MESOSCALE DISCUSSION 1513
NWS STORM PREDICTION CENTER NORMAN OK
0206 PM CDT MON AUG 04 2014

AREAS AFFECTED...NRN IA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 041906Z - 042030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED LARGE HAIL WILL BE POSSIBLE THIS AFTERNOON WITH
THE STRONGEST STORMS...BUT SEVERE STORM COVERAGE/INTENSITY SHOULD
REMAIN TOO MARGINAL FOR A SEVERE THUNDERSTORM WATCH.

DISCUSSION...SURFACE TEMPERATURES HAVE WARMED INTO THE LOW 80S
ACROSS IA EARLY THIS AFTERNOON...WHILE SURFACE DEWPOINTS HAVE
REMAINED LARGELY IN THE MID 60S.  THIS HAS RESULTED IN THE REMOVAL
OF CONVECTIVE INHIBITION...WHILE MLCAPE HAS INCREASED TO ABOUT 1500
J/KG.  MEANWHILE...DEEP-LAYER VERTICAL SHEAR IS MOST FAVORABLE FOR
PERSISTENT/SUPERCELL STORMS ACROSS THE WRN HALF OF IA.  THE MAIN
UNCERTAINTY WILL BE STORM COVERAGE IN THE AREA OF GREATER RISK FOR
LONGER-LIVED STORMS ACROSS NW IA...WHILE THE INDIVIDUAL STORMS WILL
BE SHORTER-LIVED AND AT MOST A MARGINAL HAIL RISK CLOSER TO THE MS
RIVER.  SINCE LARGE-SCALE FORCING FOR ASCENT IS WEAK...STORM
DEVELOPMENT FARTHER W WILL LIKELY DEPEND ON SHALLOW ASCENT ALONG THE
DIFFUSE REINFORCING FRONTAL SEGMENT DRIFTING SWD FROM MN INTO NRN IA
THIS AFTERNOON.  BASED ON THIS SETUP...THE NEED FOR A SEVERE
THUNDERSTORM WATCH APPEARS TO BE LOW THIS AFTERNOON...BUT THIS AREA
WILL CONTINUE TO BE MONITORED FOR CHANGES TO THE CURRENT FORECAST
REASONING.

..THOMPSON/CORFIDI.. 08/04/2014

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

ATTN...WFO...DVN...ARX...MPX...DMX...FSD...

LAT...LON   43519499 43499370 43429285 43129220 42739174 42299174
            41799211 41659295 41799440 42149553 42529625 42929653
            43379646 43519499

Nearby

Mesoscale Discussions in Iowa, 2014 Every mesoscale discussion in 2014

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.