MESOSCALE PRECIPITATION DISCUSSION 0029
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
517 PM EDT TUE APR 07 2015
 
AREAS AFFECTED...FAR SOUTHERN IL...FAR SOUTHERN IN...KY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 072115Z - 080200Z
 
SUMMARY...STRONG CONVECTIVE LINE WILL CONTINUE TO FOCUS INTENSE
RAINFALL RATES ALONG WITH POTENTIAL FOR AREAS OF TRAINING. THIS
WILL CONTRIBUTE TO ADDITIONAL FLASH FLOOD CONCERNS.

DISCUSSION...VERY COLD-TOPPED CONVECTION ASSOCIATED WITH AN
ELONGATED W/E MCS IS IN THE PROCESS OF CROSSING THE OH RIVER AND
SHOULD CONTINUE TO GENERALLY BOW E/SE THROUGH THE EARLY EVENING
HOURS. THE MCS WHICH HAS SUSTAINED A COLD POOL THROUGH MUCH OF ITS
EVOLUTION TODAY CONTINUES TO INTERACT WITH A MOIST AND
INCREASINGLY UNSTABLE BOUNDARY LAYER THAT IS ADVANCING NORTHEAST
UP INTO THE OH VALLEY AS PART OF A LARGER SCALE WARM AIR ADVECTION
PATTERN. THE CONVECTION IS EMBEDDED WITHIN RELATIVELY DIVERGENT
FLOW ALOFT AS SUGGESTED BY THE LATEST WV IMAGERY AND IS TAKING
ADVANTAGE OF SOME MID LEVEL DRY AIR. WHILE THIS IS SUPPORTING AN
INHERENT SEVERE MODE TO SOME OF THE CONVECTION...THE ACTIVITY IS
GENERALLY ORIENTED W/E AND IS NEARLY PARALLEL TO THE MEAN LAYER
STEERING FLOW. THIS IS RESULTING IN PERIODIC TRAINING OF PORTIONS
OF THE MCS...AND IS RESULTING IN SHORT TERM RAINFALL AMOUNTS OF 2
TO 4 INCHES WITH ISOLATED HEAVIER AMOUNTS.

OVER THE NEXT FEW HOURS...THE CONVECTION WILL ADVANCE E/SE AND
CONTINUE TO TAKE ADVANTAGE OF RELATIVELY STRONG DIURNAL HEATING
AND UPSTREAM MOISTURE TRANSPORT FROM THE MID MS VALLEY FOR
ADDITIONAL HEAVY RAINS AND POTENTIAL FOR TRAINING/BACK-BUILDING OF
CELLS. THE LATEST VIS SUGGESTS AN INCREASINGLY AGITATED CU/TCU
FIELD OVER FAR SOUTHEAST MO/SOUTHERN IL WHICH IS ALIGNED WELL WITH
THE W/SW LOW LEVEL JET OVER THE REGION. SO...THE SOUTHWEST FLANK
OF THE CURRENT MCS IS LIKELY TO STAY ACTIVE OVER THE NEXT FEW
HOURS. MEANWHILE...THE CONVECTION WILL LOCALLY BE FALLING OVER
AREAS THAT SAW RECENT HEAVY RAIN...AND SO WITH SATURATED GROUND
LOCALLY...ANY ADDITIONAL HEAVY RAIN WILL CAUSE FLASH FLOODING.

ORRISON

ATTN...WFO...ILN...JKL...LMK...PAH...RLX...

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

LAT...LON   38728421 38638333 38208273 37478291 36938360 
            36788498 36768717 36858858 37118921 37388945 
            37628957 37858922 37858781 38188643 38478546 
            38648481