Mesoscale Discussion 1721

Issued

Aug 8, 2012, 4:10 PM CDT (21:10 UTC)

Expired

Aug 8, 2012, 5:45 PM CDT

In force

95 min

Issued by

the Storm Prediction Center

The Des Moines radar (KDMX), 93 km from the middle of the area, began a volume at 21:11 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

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• Severe Thunderstorm Watch 566Aug 8, 4:55 PM CDT

370 
ACUS11 KWNS 082111
SWOMCD
SPC MCD 082110
IAZ000-MOZ000-KSZ000-NEZ000-082245-

MESOSCALE DISCUSSION 1721
NWS STORM PREDICTION CENTER NORMAN OK
0410 PM CDT WED AUG 08 2012

AREAS AFFECTED...CENTRAL AND SOUTH CENTRAL IA

CONCERNING...SEVERE THUNDERSTORM WATCH 565...

VALID 082110Z - 082245Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 565
CONTINUES.

SUMMARY...THE POTENTIAL FOR STRONG TO SEVERE STORMS WILL ADVANCE EWD
THIS AFTERNOON ACROSS CENTRAL AND SOUTH CENTRAL IA.  GIVEN
DOWNSTREAM DESTABILIZATION AND THE CURRENT SPEED OF THE LINE OF
STORMS...LOCAL AREAL EXTENSION OF THIS WATCH MAY BE NEEDED.
MEANWHILE...NEW TSTM DEVELOPMENT OVER ERN AND SERN NEB COULD WARRANT
A NEW WW ISSUANCE YET THIS AFTERNOON OR EARLY EVENING.

DISCUSSION...AT 2045Z...REGIONAL RADAR IMAGERY SHOWED A LINE OF
STORMS EXTENDING FROM BOONE COUNTY IA SSWWD INTO MADISON COUNTY IA.
THESE STORMS WERE MOVING EWD AT 22 KT AND WILL EXIT THE NERN EXTENT
OF THIS WW BY 22Z AND THE REST OF THE WATCH BY 23Z.  ADDITIONAL
SURFACE HEATING OVER ERN/SERN IA...DOWNSTREAM OF THE CENTRAL IA
STORMS AND IN THE WAKE OF AN MCV AND ATTENDANT CLOUDINESS MOVING EWD
THROUGH SRN WI AND NRN/CENTRAL IL...HAS RESULTED IN MODERATE
DESTABILIZATION /MLCAPE 1500-2000 J PER KG/.  THIS INSTABILITY
COMBINED WITH COLD POOL ATTENDANT TO THE EWD MOVING MCS SUGGESTS
THIS ACTIVITY WILL MAINTAIN AN EWD TRAJECTORY WITH A THREAT FOR
DAMAGING WINDS AND HAIL.  THUS...LOCAL WFO AREAL EXTENSION MAY BE
NEEDED FROM MARSHALL AND TAMA COUNTIES IA SWD TO DAVIS COUNTY IA
PRIOR TO 22Z.

TRENDS WILL BE MONITORED FARTHER DOWNSTREAM INTO SERN IA AND NERN MO
WHERE MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR OF 30-40 KT ARE
SUPPORTIVE FOR SUSTAINING ORGANIZED STORMS. MODELS SUGGEST THIS
POTENTIAL INTO THE EARLY EVENING...BUT STABILIZING TRENDS WITH THE
EVENTUAL LOSS OF DAYTIME HEATING MAY LIMIT THE E/SEWD EXTENT OF THE
ONGOING CENTRAL IA STORMS INTO SERN IA AND NERN MO.

MEANWHILE...FARTHER W...ISOLATED STORMS HAVE DEVELOPED INVOF THE
SURFACE LOW IN EAST CENTRAL NEB AND SSEWD ALONG THE WARM FRONT INTO
SERN NEB.  THE AIR MASS IS MODERATELY UNSTABLE ACROSS THIS REGION
WITH EFFECTIVE BULK SHEAR OF 35-40 KT SUPPORTIVE OF SEVERE STORMS.
AREAS TO THE W AND SW OF WW 565 WILL ALSO BE MONITORED FOR WW
ISSUANCE YET THIS AFTERNOON OR EARLY EVENING.

..PETERS.. 08/08/2012

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

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

LAT...LON   42179234 41679182 40439160 40019214 39809408 39829516
            39729563 40079600 40639635 41159663 41539681 42049562
            42269507 42299405 42179234

Mesoscale Discussions in Iowa, 2012Mesoscale Discussions in Missouri, 2012Mesoscale Discussions in Nebraska, 2012Every mesoscale discussion in 2012

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.