Mesoscale Discussion 1698

Issued

Aug 4, 2012, 10:26 AM CDT (15:26 UTC)

Expired

Aug 4, 2012, 11:15 AM CDT

In force

49 min

Issued by

the Storm Prediction Center

Chance of a watch

80%

The Quad Cities radar (KDVN), 25 km from the middle of the area, began a volume at 15:28 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 557Aug 4, 10:55 AM CDT
• Severe Thunderstorm Watch 558Aug 4, 1:50 PM CDT

563 
ACUS11 KWNS 041527
SWOMCD
SPC MCD 041526 COR
INZ000-ILZ000-WIZ000-IAZ000-MOZ000-041615-

MESOSCALE DISCUSSION 1698
NWS STORM PREDICTION CENTER NORMAN OK
1026 AM CDT SAT AUG 04 2012

AREAS AFFECTED...PORTIONS OF IA/NERN MO/CENTRAL-NRN IL/SRN WI

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 041526Z - 041615Z

CORRECTED FOR DISCUSSION AREA REFERENCE

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...A CONTINUED INCREASE IN TSTM COVERAGE AND INTENSITY IS
EXPECTED INTO THE AFTERNOON HOURS. SVR TSTMS WITH A THREAT FOR
DAMAGING WINDS AND PERHAPS LARGE HAIL ARE EXPECTED. A WW WILL LIKELY
BE NEEDED FOR PORTIONS OF THIS AREA BY 16Z-17Z.

DISCUSSION...TSTMS CONTINUE TO INCREASE IN COVERAGE IN ADVANCE OF A
COLD FRONT EXTENDING FROM ERN MN SWD THROUGH CENTRAL IA/NWRN MO. A
QUASI-STNRY FRONT ACROSS NRN MO IS ALSO HELPING TO FOCUS LOW-LEVEL
CONVERGENCE. OBJECTIVE ANALYSIS INDICATES THE ATMOSPHERE IN ADVANCE
OF THE AREA OF CONVECTION CONTINUES TO DESTABILIZE WITH DIURNAL
HEATING...WITH MLCAPE VALUES CURRENTLY 1000-2000 J/KG. STRONGER FLOW
ALOFT IS RESULTING IN EFFECTIVE BULK SHEAR VALUES OF 40-50
KT...SUFFICIENT FOR MULTICELL STORM ORGANIZATION WITH SOME SUPERCELL
STRUCTURES POSSIBLE. AS FURTHER DESTABILIZATION OCCURS...THE PRIMARY
THREATS WILL BE DAMAGING WINDS...ALTHOUGH LARGE HAIL IS POSSIBLE
WITH ANY SUPERCELLS THAT DEVELOP.

A GRADUAL INCREASE IN COVERAGE IS EXPECTED THROUGH EARLY AFTERNOON
AS A SEASONABLY STRONG UPPER LEVEL TROUGH OVER THE CENTRAL/NRN
PLAINS MOVES EWD PROVIDING ADDITIONAL FORCING FOR ASCENT. WATER
VAPOR LOOPS ALSO SUGGEST A WEAKER DISTURBANCE EMBEDDED WITHIN
MONSOONAL FLOW ON THE NRN PERIPHERY OF MID-LEVEL ANTICYCLONE WILL
ALSO PROVIDE ADDITIONAL FORCING.

..BUNTING/THOMPSON.. 08/04/2012

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

ATTN...WFO...LOT...ILX...MKX...LSX...DVN...ARX...DMX...EAX...

LAT...LON   42578790 41458738 40058783 39678930 39749116 39989352
            41179404 42169406 42969355 43019046 42578790

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