AREAS AFFECTED...NERN AND EAST CENTRAL MO/WRN IL CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 260643Z - 260815Z PROBABILITY OF WATCH ISSUANCE...60 PERCENT SUMMARY...A SVR TSTM WATCH MAY NEED TO BE ISSUED OVERNIGHT FOR PARTS OF NERN AND EAST CENTRAL MO INTO WRN IL. THE ENVIRONMENT ACROSS THIS REGION IS CONDUCIVE TO SUPPORT AND SUSTAIN TSTM DEVELOPMENT INTO EARLY THIS MORNING...WITH THE POTENTIAL FOR A BOWING LINE OF STORMS TO MOVE ESEWD THROUGH THIS AREA. DAMAGING WINDS SHOULD BE THE PRIMARY THREAT...THOUGH HAIL MAY OCCUR AS WELL. UPSCALE GROWTH POTENTIAL IS BEING MONITORED WITH THE CLUSTER OF STORMS IN NRN MO...AND THIS TREND COULD BE THE IMPETUS FOR NEW WW ISSUANCE. DISCUSSION...AT 0630Z...REGIONAL RADAR IMAGERY INDICATED TSTMS OVER NRN MO WERE INCREASING IN AREAL COVERAGE AND MOVING TO THE ESE AT 30-35 KT. MEANWHILE...RADAR IMAGERY AND SURFACE OBSERVATION ANALYSIS SHOWED A COMPOSITE CONVECTIVE OUTFLOW BOUNDARY EXTENDING WNWWD FROM FAR SRN IND THROUGH SERN IL TO WEST CENTRAL IL. SEVERAL ROUNDS OF TSTMS THAT HAVE AND CONTINUE TO MOVE THROUGH ERN IL AND SRN IND ARE REINFORCING THE OUTFLOW BOUNDARY. THE AIR MASS ALONG AND W OF THIS WNW-ESE ORIENTED BOUNDARY INTO ERN MO REMAINS MODERATELY UNSTABLE WITH MUCAPE UP TO 2000-2500 J/KG. A MIDLEVEL IMPULSE...CURRENTLY LOCATED OVER IA PER WATER VAPOR IMAGERY...IS EXPECTED TO UNDERGO SOME AMPLIFICATION AS IT TRACKS INTO IL THE NEXT SEVERAL HOURS. ATTENDANT HEIGHT FALLS WITH THIS FEATURE AND LOW LEVEL WAA WITHIN THE NOSE OF A 45-50 KT WLY LLJ SHOULD PROVIDE SUFFICIENT FORCING FOR ASCENT TO ALLOW THE NRN MO TSTM CLUSTER TO PERSIST OVERNIGHT. THESE FACTORS COMBINED WITH THE ERN EXTENT OF STEEP MIDLEVEL LAPSE RATES EXTENDING INTO THIS REGION FAVOR UPSCALE GROWTH INTO A FORWARD PROPAGATING MCS. 00Z 4 KM WRF NMM/NSSL BOTH SUPPORT THIS SCENARIO. THE 03Z AND 04Z HRRR RUNS SUGGEST A SIMILAR SCENARIO FOR A BOWING STRUCTURE...BUT INDICATED A SLOWER UPSCALE GROWTH PROCESS. ..PETERS/HART.. 06/26/2013 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...PAH...ILX...LSX...DVN...EAX... LAT...LON 39569247 40359232 40339164 39989063 39348923 39158877 38538884 38358958 38329074 38709169 39249275 39569247
Posted on: Wed, 26 Jun 2013 06:43:48 +0000
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