Mesoscale Discussion 688

Issued

May 3, 2012, 11:18 PM CDT (04:18 UTC)

Expired

May 3, 2012, 11:45 PM CDT

In force

27 min

Issued by

the Storm Prediction Center

The Des Moines radar (KDMX), 188 km from the middle of the area, began a volume at 04:20 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.

• Severe Thunderstorm Watch 235May 3, 11:35 PM CDT
• Severe Thunderstorm Watch 236May 4, 12:55 AM CDT

421 
ACUS11 KWNS 040418
SWOMCD
SPC MCD 040418 
ILZ000-IAZ000-MOZ000-KSZ000-NEZ000-040445-

MESOSCALE DISCUSSION 0688
NWS STORM PREDICTION CENTER NORMAN OK
1118 PM CDT THU MAY 03 2012

AREAS AFFECTED...NRN MO/SRN AND SERN IA AND WRN/NRN IL

CONCERNING...TORNADO WATCH 232...234...

VALID 040418Z - 040445Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 232...234...CONTINUES.

SUMMARY...ONGOING TSTM CLUSTER LOCATED OVER SERN IA INTO NWRN IL
WILL CONTINUE TO MOVE ESE DURING THE LATE EVENING/EARLY OVERNIGHT
PERIOD WITH A NEW WW POSSIBLE BY 05Z AS WW 232 AND WW 233 ARE
SCHEDULED TO EXPIRE AT THAT TIME.  IN ADDITION TO A THREAT FOR SVR
STORMS WITH THIS COMPLEX...HEAVY RAIN RATES OF 1-2+ INCH PER HOUR
WILL PERSIST AS STORMS TRAIN ESE WITHIN A 35 MILE WIDE CORRIDOR
EXTENDING FROM LOUISA COUNTY IA TO LA SALLE COUNTY IL.

TSTMS HAVE CONTINUED TO INCREASE IN COVERAGE AND INTENSITY ACROSS
NWRN MO INTO FAR NERN KS.  A TORNADO THREAT AND POTENTIAL FOR LARGE
HAIL AND DAMAGING WINDS ARE POSSIBLE WITH THIS ACTIVITY.

DISCUSSION...LATE EVENING SURFACE ANALYSIS SHOWED A ZONE OF LOW
LEVEL CONVERGENCE EXTENDING FROM NEAR CHICAGO SWWD INTO WEST CENTRAL
IL AND THEN WWD THROUGH FAR NRN MO.  OBJECTIVE ANALYSES INDICATED
EFFECTIVE SRH OF 100-200 M2/S2 INVOF THE CONVERGENCE ZONE WHERE A
SSWLY 30-40 KT LLJ WAS OBSERVED PER WIND PROFILERS AND WSR-88D VWP
DATA.  THIS SUGGESTS THE TORNADO THREAT REMAINS NONZERO WITH THE
GREATEST TORNADO THREAT POTENTIAL ATTENDANT TO THE DISCRETE STORMS
IN NWRN MO/FAR NERN KS...THOUGH THE TORNADO THREAT CANNOT BE RULED
OUT WITH THE ACTIVITY ALONG THE SRN EXTENT OF THE SERN IA/NWRN IL
TSTM COMPLEX.

IN ADDITION...RECENT RADAR IMAGERY OVER NWRN IL INDICATED A N-S LINE
OF TSTMS DEVELOPING FROM HENRY COUNTY TO MERCER COUNTY...WHICH MAY
BE THE BEGINNING OF A DAMAGING WIND THREAT AS THIS LINE ADVANCES
EWD.  GIVEN A SSWLY LLJ WILL CONTINUE TO FEED MODERATE INSTABILITY
INTO THE SWRN-SRN EXTENT OF THIS TSTM COMPLEX MAINTAINING NEW
DEVELOPMENT...A NEW WW WILL LIKELY BE COORDINATED SOON FOR PARTS OF
NRN/CENTRAL IL.

..PETERS.. 05/04/2012

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

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

LAT...LON   40599574 40659487 41499514 41559157 41879131 41809025
            41618978 41558918 40928900 40368801 39878929 39489069
            39159132 39299261 39309328 39199418 39459442 39559511
            39699532 40599574

Mesoscale Discussions in Missouri, 2012Mesoscale Discussions in Iowa, 2012Mesoscale Discussions in Illinois, 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.