MESOSCALE PRECIPITATION DISCUSSION 0040
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM EST SAT FEB 24 2018

AREAS AFFECTED...SOUTHEAST MO...SOUTHERN IL...SOUTHERN
IN...CENTRAL/SOUTHERN OH...WESTERN/NORTHERN KY

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 242200Z - 250400Z

SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS WILL CONTINUE TO LIFT
NORTHEAST UP ALONG THE OH RIVER VALLEY THROUGH THE EVENING HOURS.
FLASH FLOODING WILL BE LIKELY GIVEN THE SATURATED SOIL CONDITIONS.

DISCUSSION...AN UPPER TROUGH IS ADVANCING TOWARD THE UPPER MIDWEST
LATE THIS AFTERNOON WHICH IS PROMOTING A STRONG WARM AIR ADVECTION
AND MOISTURE TRANSPORT PATTERN DOWNSTREAM ACROSS THE OH VALLEY.
ALREADY THE LATEST RADAR IMAGERY SHOWS A BROKEN AXIS OF SHOWERS
AND THUNDERSTORMS FOCUSING ALONG AND GENERALLY NORTH OF A WARM
FRONT FROM SOUTHEAST MO AND SOUTHERN IL EAST ACROSS MUCH OF
CENTRAL/WESTERN KY AND SOUTHERN IN.

AS SUPPORTED BY A CONSENSUS OF THE LATEST CAM GUIDANCE...THIS
ACTIVITY WILL CONTINUE TO ADVANCE GENERALLY NORTHEAST OVER THE
NEXT SEVERAL HOURS AND WILL TEND TO BECOME A BIT MORE
CONCENTRATED/FOCUSED AS LARGER SCALE FORCING WITH THE APPROACH OF
THE UPSTREAM TROUGH ARRIVES IN CONJUNCTION WITH A STRONGER
SOUTHWEST LOW LEVEL JET. THIS WILL DRIVE NOT ONLY STRONGER
ISENTROPIC ASCENT NORTH OF THE WARM FRONT...BUT ALSO HIGH PWATS
WITH TIME THAT SHOULD REACH UP OVER 1.25 INCHES AND LOCALLY OVER
1.5 INCHES BY LATE EVENING. INSTABILITY IS EXPECTED TO BE RATHER
MODEST OVERALL...BUT LARGER SCALE ASCENT SHOULD TEND TO OVERCOME
THIS AND STILL FOSTER AN EXTENSIVE AXIS OF HEAVY RAINFALL WITH
POTENTIAL FOR SW/NE ORIENTED TRAINING OF CONVECTIVE CELLS.

EXPECT RAINFALL RATES TO REACH UP AS HIGH AS 1.5 INCHES/HR...WITH
STORM TOTALS THROUGH 03Z OF AS MUCH AS 2 TO 4 INCHES WITH ISOLATED
HEAVIER TOTALS. THIS IS LIKELY TO CAUSE SIGNIFICANT RUNOFF
PROBLEMS AND FLASH FLOODING GIVEN MULTIPLE ROUNDS OF HEAVY RAIN
OVER THE LAST WEEK.

ORRISON

ATTN...WFO...ILN...ILX...IND...JKL...LMK...LSX...MEG...OHX...
PAH...PBZ...RLX...

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

LAT...LON   40228333 40168177 39458139 38548216 38098292
            37648394 37328469 36938568 36638691 36458861
            36428967 36589054 37199074 37819031 38598893
            39178723 39668543