Severe Storm Outlook Narrative (AC)
Issued by NWS

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000 ACUS11 KWNS 231619 SWOMCD SPC MCD 231618 INZ000-ILZ000-231815- MESOSCALE DISCUSSION 1602 NWS STORM PREDICTION CENTER NORMAN OK 1118 AM CDT SAT AUG 23 2014 AREAS AFFECTED...NRN AND EASTERN ILLINOIS INTO WRN INDIANA CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 231618Z - 231815Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...IN ADDITION TO THE RISK FOR VERY HEAVY RAINFALL AND FREQUENT CLOUD TO GROUND LIGHTNING...THE POTENTIAL FOR STRONG WIND GUSTS MAY BEGIN TO INCREASE WITH STORMS OVERSPREADING THE REGION THIS AFTERNOON. THE PROBABILITY OF A SEVERE WEATHER WATCH ISSUANCE STILL SEEMS LOW...BUT TRENDS IN STORM COVERAGE AND ORGANIZATION WILL CONTINUE TO BE MONITORED. DISCUSSION...VIGOROUS CONVECTION PERSISTS WITH A BAND OF FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH A WEAK SHORT WAVE IMPULSE NOW PROGRESSING AROUND/THROUGH THE CREST OF MID-LEVEL RIDGING ACROSS NORTHERN ILLINOIS AND SOUTHERN WISCONSIN. A LINE OF THUNDERSTORMS APPEARS LIKELY TO CONTINUE SPREADING EASTWARD INTO THE CHICAGO METROPOLITAN AREA THROUGH THE 18-19Z TIME FRAME...BUT THE STRONGEST ACTIVITY IS BECOMING FOCUSED ON THE SOUTHERN FLANK OF THE LINE ADVANCING NEAR/NORTH THROUGH EAST OF PEORIA...AIDED BY INFLOW OF SOMEWHAT WARMER AND MORE MOIST AIR. AS INHIBITION FOR VERY MOIST BOUNDARY LAYER PARCELS /WITH SURFACE DEW POINTS IN THE MID 70SF/ CONTINUES TO WEAKEN WITH INSOLATION ...FURTHER INTENSIFICATION OF CONVECTION OR SUBSTANTIVE NEW DEVELOPMENT APPEARS PROBABLE DURING THE NEXT FEW HOURS ACROSS OR TO THE EAST SOUTHEAST OF THE PEORIA/BLOOMINGTON/DECATUR AREA. DESPITE THE PRESENCE OF WEAK TO MODEST MID-LEVEL LAPSE RATES... SEASONABLY HIGH MOISTURE CONTENT...WITH PRECIPITABLE WATER WELL IN EXCESS OF TWO INCHES...IS SUPPORTING SIZABLE CAPE AND THE POTENTIAL FOR HEAVY PRECIPITATION LOADING. THIS COULD BEGIN TO GRADUALLY CONTRIBUTE TO AN INCREASING RISK FOR STRONG DOWNBURSTS...AND PERHAPS AN EXPANDING/STRENGTHENING SURFACE COLD POOL. WITH DEEP LAYER MEAN FLOW FIELDS TRANSITIONING FROM LIGHT WESTERLY TO LIGHT NORTHWESTERLY ACROSS ILLINOIS INTO INDIANA...THE TENDENCY MAY BE FOR STRONGEST STORMS TO EVENTUALLY TAKE ON A MORE SOUTHEASTERLY PROPAGATION THROUGH THE AFTERNOON HORUS. ..KERR/MEAD.. 08/23/2014 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...IWX...IND...PAH...LOT...ILX...LSX... LAT...LON 39718938 40288943 40708899 41198905 41138891 42298909 41958822 41378739 40918681 40528624 39408628 38308785 39718938

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