AREAS AFFECTED...EAST CENTRAL MO/WRN IL TO SERN MO/SRN IL CONCERNING...SEVERE THUNDERSTORM WATCH 371... VALID 261046Z - 261215Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 371 CONTINUES. SUMMARY...THREAT FOR DAMAGING WINDS PERSISTS ACROSS EAST CENTRAL MO AND WRN IL...WITH RECENT INCREASE IN FORWARD SPEED TO 30 KT. SUBSEQUENT DOWNSTREAM THREAT HAS WARRANTED AN EXPANSION OF WW 371 INTO THE ST LOUIS METRO AREA. TRENDS WILL BE MONITORED FOR ADDITIONAL EXPANSION OF WW 371...AND THE POTENTIAL NEED FOR A NEW SVR TSTM WATCH INTO PARTS OF MAINLY SRN IL. HOWEVER...THE PROBABILITY FOR NEW WATCH ISSUANCE IS 20-30 PERCENT AT THE PRESENT TIME DISCUSSION...AT 10Z...MOSAIC RADAR IMAGERY SHOWED A RELATIVELY COMPACT CLUSTER OF TSTMS EXTENDING FROM EAST CENTRAL MO INTO ADJACENT COUNTIES OF WRN IL...WITH THE LEADING EDGE LOCATED 15 NNW KSTL-25 W KSTL. THE DOWNSTREAM ENVIRONMENT FROM THE ONGOING STORMS TO SERN MO AND SRN IL REMAINS MODERATELY UNSTABLE AND SUFFICIENTLY SHEARED TO SUSTAIN THE SEWD MOVEMENT OF THIS TSTM CLUSTER. IF THE FORWARD SPEED INCREASES FURTHER /GREATER THAN 30 KT/...THEN THE OVERALL THREAT FOR DAMAGING WINDS SHOULD CONCURRENTLY INCREASE. THIS WOULD WARRANT AN ADDITIONAL EXPANSION SSEWD OF THIS WATCH WITHIN THE WFO STL/ILX COUNTY WARNING AREAS. FORCING FOR ASCENT ATTENDANT TO A MIDLEVEL IMPULSE TRACKING SEWD INTO IL AND THE LOWER OH VALLEY THIS MORNING SHOULD SUSTAIN NEW TSTM DEVELOPMENT WITHIN THE ONGOING CLUSTER. A 45-55 KT WLY LOW LEVEL JET EXTENDS INTO THE WRN EXTENT OF THE TSTM COMPLEX...AND THIS JET IS FORECAST TO UNDERGO SOME WEAKENING AFTER 12Z. UNTIL THEN...A DAMAGING WIND THREAT COULD SPREAD SEWD /SOUTH OF WW 371/... ESPECIALLY IF THE FORWARD SPEED INCREASES. HOWEVER...THIS TSTM CLUSTER HAS NOT PRODUCED ANY SVR WEATHER SO FAR...AND THE CONFIDENCE FOR THIS TREND TO CHANGE IS LOW...ESPECIALLY GIVEN THE AFOREMENTIONED DECREASE IN THE LLJ EXPECTED BY MID MORNING. ..PETERS.. 06/26/2013 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...PAH...ILX...LSX... LAT...LON 38749141 39329127 39419082 39558996 39688910 38988829 38558785 38118772 37608801 37238839 37208864 37208908 37719014 38749141
Posted on: Wed, 26 Jun 2013 10:47:22 +0000