MESO: Mesoscale Discussion 1474

ACUS11 KWNS 071848
SWOMCD
SPC MCD 071847
IAZ000-MNZ000-SDZ000-071945-

MESOSCALE DISCUSSION 1474
NWS STORM PREDICTION CENTER NORMAN OK
0147 PM CDT TUE JUL 07 2009

AREAS AFFECTED...PARTS OF SERN SD / SWRN MN / NWRN-CNTRL IA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 071847Z - 071945Z

SEVERE POTENTIAL WILL GRADUALLY INCREASE THIS AFTERNOON ACROSS PARTS
OF SERN SD AND EVENTUALLY EXTEND SEWD INTO SWRN MN AND NWRN/CNTRL IA
BY LATE AFTERNOON/EARLY EVENING. SURFACE-BASED TSTM INITIATION
TRENDS WILL BE MONITORED FOR A POSSIBLE WW IN THE NEXT HOUR OR
SO...OVER THE NWRN HALF OF THE MCD AREA.

RECENT SATELLITE/SURFACE COMPOSITE ANALYSIS SHOWS A 1005 MB LOW
INVOF PIR WITH A OUTFLOW BOUNDARY/WARM FRONTAL SEGMENT EXTENDING
SEWD TO NEAR DSM. AN OUTFLOW BOUNDARY FROM ELEVATED STORMS OVER
SERN MN IS DRAPED FROM N-CNTRL IA NWWD TO AN INTENSIFYING TSTM OVER
SPINK COUNTY SD. AIRMASS N OF WARM FRONTAL SEGMENT IS CONTINUING TO
DESTABILIZE THIS AFTERNOON...OWING IN LARGE PART TO STRONG DIABATIC
SURFACE HEATING S OF CONVECTIVE DEBRIS CLOUDS THAT ARE LOCATED
GENERALLY N OF NRN OUTFLOW BOUNDARY. ENHANCED LOW LEVEL CONVERGENCE
IMMEDIATELY NEAR THE OUTFLOW BOUNDARY OVER S-CNTRL IA WILL LEAD TO
FURTHER TSTM DEVELOPMENT WITH CAPPING HAVING BEEN BREACHED IN THE
PAST 30 MINUTES.

DESPITE ONLY MODEST MID-LEVEL WLY FLOW ALOFT ACCORDING TO LOCAL VWP
DATA...LOCALLY BACKED SURFACE WINDS N OF AFOREMENTIONED BOUNDARIES
OVER SD WILL ENHANCE OTHERWISE MARGINAL DEEP LAYER SHEAR OVER THE
REGION. THE GREATEST POTENTIAL IN THE NEXT FEW HOURS FOR ORGANIZED
STORMS WILL LIKELY BE OVER PARTS OF ERN SD ONCE SURFACE-BASED
TRANSITION OCCURS. THE MAIN THREATS WITH THE STRONGER STORMS WILL
BE LARGE HAIL/ISOLD DMGG WIND GUSTS.

..SMITH.. 07/07/2009

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

ATTN...WFO...MPX...DMX...FSD...ABR...

LAT...LON 41319312 43759929 44439992 44989987 45229910 45209835
44959732 44249578 42479275 41949241 41429241 41319312

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.