SPC MD 1644

MD 1644 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS CENTRAL-SERN IA…WRN IL…NERN MO.


MESOSCALE DISCUSSION 1644
NWS STORM PREDICTION CENTER NORMAN OK
0325 PM CDT SUN JUL 29 2012

AREAS AFFECTED...PORTIONS CENTRAL-SERN IA...WRN IL...NERN MO.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 292025Z - 292230Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...CONVECTIVE POTENTIAL IS INCREASING OVER PORTIONS
CENTRAL/SERN IA...WITH RISK FOR ANY SUSTAINED TSTMS TO PRODUCE
DAMAGING GUSTS AND LARGE HAIL.  RESULTING ACTIVITY MAY GROW UPSCALE
INTO ORGANIZED TSTM CLUSTER WITH LOCALLY ENHANCED WIND
POTENTIAL...AND MOVE SEWD OVER PORTIONS NERN MO AND WRN IL INVOF SFC
BOUNDARY.

DISCUSSION...SFC MESOANALYSIS SHOWS DIFFUSE CYCLONE OVER WRN
IA...WITH TROUGH EXTENDING SSWWD TO WEAK LOW IN NERN KS.  WARM
FRONT...DEMARCATING NRN PORTION OF VERY HOT/WELL-MIXED BOUNDARY
LAYERS IN CENTRAL/SRN PLAINS...WAS DRAWN FROM KS LOW SEWD ACROSS MKC
AREA AND SWRN MO.  QUASISTATIONARY DIFFERENTIAL-HEATING AND
CONVERGENCE BOUNDARY...MARKING WRN RIM OF EARLIER CLOUD COVER AND
PRECIP...WAS EVIDENT FROM BRL AREA NWWD ACROSS CENTRAL IA TO NEAR
SPW.  VIS IMAGERY SHOWS DEEPENING CU ALONG AND WITHIN ABOUT 60 NM SW
OF THAT BOUNDARY.  AIR MASS BETWEEN BOUNDARY AND WARM FRONT...AND E
OF SFC TROUGH...IS CHARACTERIZED BY STG SFC HEATING AND DEW POINTS
MID-UPPER 60S F...OFFSETTING MEAGER LOW-MIDDLE LEVEL LAPSE RATES
ENOUGH TO YIELD MLCAPE 1500-2500 J/KG IN FCST SOUNDINGS...BY 21-22Z
TIME FRAME.  BACKED/ELY SFC FLOW COMPONENT WILL CONTINUE TO ENHANCE
BOUNDARY-LAYER HODOGRAPHS AND STORM-RELATIVE INFLOW FOR ANY TSTMS
THAT FORM ALONG AND E OF BOUNDARY.  RESULTANT EFFECTIVE SRH 150-200
J/KG AND EFFECTIVE SHEAR MAGNITUDES 55-65 KT AND MAY SUPPORT AT
LEAST TRANSIENT SUPERCELL STRUCTURES...AS WELL AS POTENTIAL FOR
BOWS.

..EDWARDS/CORFIDI.. 07/29/2012

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

ATTN...WFO...ILX...LSX...DVN...DMX...EAX...

LAT...LON   40119256 41789364 42709426 42149210 40578942 39469044
            39129192 40119256

via SPC Forecast Products http://www.spc.noaa.gov/products/md/md1644.html