MESOSCALE PRECIPITATION DISCUSSION 0150
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
813 PM EDT FRI APR 28 2017

AREAS AFFECTED...LOWER AND CENTRAL OHIO RIVER VALLEY...BOOTHEEL OF
MO

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

VALID 290015Z - 290700Z

SUMMARY...INCREASING CONVECTION THAT WILL BE SLOW MOVING AND
TRAINING ALONG THE OHIO RIVER WITH INCREASING EFFICIENCY THROUGH
THE EARLY OVERNIGHT HOURS POSING LIKELY FLASH FLOOD CONDITIONS. 

DISCUSSION...GOES-16/EAST WV LOOP SHOWS A RELATIVELY FLAT
SHORTWAVE ACROSS NW OH WITH THE TRAILING TROF SW ACROSS CENTRAL
IND/IL WITH A MCS TRACKING ACROSS CENTRAL IND.  THIS MCS IS AT THE
APEX OF SOUTHWESTERLY LOW LEVEL JET/WAA REGIME OVERRUNNING A WARM
FRONT THAT EXTENDS FROM LWV...N OF LOU AND S OF CVG.  THIS COMPLEX
HAS BEEN PRODUCING 1.5-2.5" RAIN AS IT TRACKED THROUGH WEST
CENTRAL IND...AND WILL LIKELY MAINTAIN AS IT CROSSES INTO LOWER
FFG VALUES ACROSS SE IND/SW OH IN THE NEXT HOUR OR SO. 

AS THE EVENING PROGRESSES LOW LEVEL FLOW IS EXPECTED TO INCREASE
AND BECOME INCREASINGLY CONFLUENT/CONVERGENT ACROSS THE LOWER OH
RIVER VALLEY JUST EAST OF STATIONARY FRONT THAT HAS BEEN LOCKED
ACROSS CENTRAL AR ACROSS SE MO TOWARD WEAK SURFACE REFLECTION NEAR
FWC IN SE IL.  CLEARING SKIES IN THE WARM SECTOR EAST OF THE
BOUNDARY IN S IL/W KY/NW TN HAS ALLOWED FOR MLCAPES TO INCREASE TO
NEAR 3000 J/KG PER RAP ANALYSIS IN TN TO 1000 J/KG IN SW IND. 
CURRENT RADAR AND WANING GOES-16 VISIBLE SHOWS THE WEAK CAP HAS
ERODED ENOUGH TO ALLOW FOR SHALLOW CONVECTION TO BLOSSOM IN S IL
AND NW TN.  UNIDIRECTIONAL FLOW DUE TO THE PASSING SHORTWAVE IN OH
AND STRENGTHENING SWLY LOW LEVEL JET WILL FAVOR CLOUD BEARING
LAYER ACROSS THE OHIO RIVER VALLEY THROUGH THE EVENING. 
STRENGTHENING LLJ AND DEEP WELL OF INSTABILITY AND
STRONG/REINFORCED FRONTAL BOUNDARY FAIRLY PARALLEL TO THE
UNIDIRECTIONAL FLOW ALLOWING FOR LOW LEVEL MST CONVERGENCE/FLUX ON
45-50KT WINDS AND TPWS TO INCREASE TO 1.75".  THIS WILL ALLOW FOR
HIGHLY EFFICIENT RAINFALL PRODUCTION WITH INDIVIDUAL CORES OF
2-2.5"/HR TOWARD 03-04Z...THIS WILL LEAD TO TOTALS OF 2-4" THROUGH
06/07Z ALONG THE OHIO RIVER POSING THOUGH WILL CONTINUE THROUGH
THE OVERNIGHT HOURS.  THIS IS IN LINE WITH 12Z HREFV2 HI-RES CAM
ENSEMBLE SOLUTIONS.

GREATEST QUESTION IS HOW FAR UPSTREAM CONVECTIVE DEVELOPMENT WILL
OCCUR AND HOW FAR DOWNSTREAM THE CONVECTION WILL MAINTAIN AT THE
EASTERN LIMB OF THE INSTABILITY WELL.  EXPECT THE WESTERN EXTENT
TO BE AT THE MS RIVER MAYBE SE WHERE APPEARANCE IN MODEL
STREAMLINES/SATELLITE MST FIELDS SUGGESTS WEAK RETURN FLOW AROUND
THE WESTERN PERIPHERY OF DEEP ANTICYCLONE CENTERED OVER THE
SOUTHERN APPALACHIANS ONLY INFLUENCING THE FLOW TO THE MS RIVER
BEFORE BECOMING DIVERGENT ACROSS CENTRAL AR.  

GALLINA

ATTN...WFO...ILN...ILX...IND...LMK...LSX...MEG...PAH...

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

LAT...LON   39968439 39798317 38858333 38498417 37168741
            36138983 36679091 37968952 38908799 39398665