MESOSCALE PRECIPITATION DISCUSSION 0487...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1039 PM EDT SUN JUL 24 2016
 
CORRECTED FOR HEADLINE

AREAS AFFECTED...CENTRAL IL...WESTERN IN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 250235Z - 250730Z
 
SUMMARY...VERY INTENSE RAINFALL RATES UP TO 3 INCHES/HR ARE
EXPECTED OVER THE NEXT FEW HOURS FROM STRONG THUNDERSTORM
ACTIVITY. FLASH FLOODING IS LIKELY.

DISCUSSION...VERY COLD-TOPPED CONVECTION IS BECOMING ORGANIZED IN
A GENERAL WSW/ENE FASHION ACROSS CENTRAL IL AND INTO NORTHWEST IN
THIS EVENING. THE ACTIVITY IS FOCUSING WITHIN A VERY MOIST AND
EXTREMELY UNSTABLE AIRMASS...CHARACTERIZED BY PWATS OF 2 TO 2.25
INCHES AND MLCAPE VALUES AS HIGH AS 4000 TO 5000 J/KG.

THE CONVECTION IS JUST OUT AHEAD OF A COLD FRONT AND IS BECOMING
INCREASINGLY FOCUSED OVER CENTRAL IL IMMEDIATELY AHEAD OF A WAVE
OF LOW PRESSURE RIDING ALONG THE FRONT. THERE IS ALSO EVIDENCE OF
A SHORTWAVE ADVANCING EAST ACROSS SOUTH-CENTRAL IA AS PER IR/WV
SAT IMAGERY WHICH FACILITATING THE WAVE DEVELOPMENT AND PROVIDING
A CORRIDOR OF LARGER SCALE ASCENT DOWNSTREAM OVER IL/IN.

THE RAP FORECASTS INDICATING SOME STRENGTHENING 250 MB
RIGHT-ENTRANCE REGION JET DYNAMICS OVERNIGHT OVER THE REGION IN
CONNECTION TO THE DEEPER LAYER TROUGH CROSSING THE UPPER
MIDWEST...AND THIS COUPLED WITH THE AFOREMENTIONED INSTABILITY AND
PROXIMITY OF THE FRONT SHOULD TEND TO ALLOW CONVECTION TO REMAIN
ACTIVE AND FOCUSED AT LEAST FOR THE NEXT SEVERAL HOURS.

HRRR AND HRRRP FORECASTS ARE SUGGESTING AS MUCH AS 3 TO 4 INCHES
THROUGH 06Z WHICH MAY BE A BIT UNDERDONE GIVEN SUCH AN INCREDIBLY
MOIST VERTICAL COLUMN WITH PWATS WELL OVER 2 INCHES. VERY COLD
CONVECTIVE TOPS...INCLUDING OVERSHOOTING TOPS AND THE DEEP
MOISTURE WILL FAVOR HIGHLY EFFICIENT RAINFALL PROCESSES THAT COULD
YIELD AS MUCH AS 3 INCHES OF RAIN IN 1 HOUR. THEREFORE...WITH THIS
AND THE POTENTIAL FOR CELL-TRAINING...VERY HEAVY RAINFALL TOTALS
ARE LIKELY THAT MAY REACH OR POSSIBLY EXCEED 5 INCHES. FLASH
FLOODING WILL BE LIKELY WITH THESE TOTALS.

ORRISON

ATTN...WFO...ILX...IND...IWX...LOT...LSX...

ATTN...RFC...NCRFC...OHRFC...

LAT...LON   40728822 40728726 40448660 39978657 39638709 
            39408807 39358908 39529015 39969052 40349029 
            40668954