MESOSCALE PRECIPITATION DISCUSSION 0745
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
416 PM EDT WED OCT 19 2016
 
AREAS AFFECTED...SOUTHERN MO...SOUTHERN IL...SOUTHERN
IND...SOUTHWEST OH...EXT NORTHERN KY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 192015Z - 200215Z
 
SUMMARY...SOLID MOISTURE/INSTABILITY WITHIN A NARROW CORRIDOR
SUPPORTS SOME TRAINING CONVECTION WITH POSSIBLE FLASH FLOODING
CONDITIONS THIS EVENING INTO OVERNIGHT HOURS. 

DISCUSSION...A STALLED BUT WELL DEFINED FRONTAL ZONE EXISTS FROM
NE OK ACROSS S MO INTO S IL/S IN TOWARD CVG.  THOUGH FLOW IS
GENERALLY WEAK AT THE SURFACE DIRECTIONAL CONVERGENCE IS FAIRLY
STRONG WITH NORTHEAST FLOW OPPOSED TO SSWLY FLOW IN GENERAL WITH
SOME CYCLONIC TURNING SEEN IN SFC WIND FIELD ALONG OHIO RIVER
VALLEY. GPS NETWORK/BLENDED TPW AND RAP ANALYSIS INDICATE FAIRLY
MOIST ENVIRONMENT WITH UP TO 1.75" CENTERED ALONG THE SOUTHERN
WABASH RIVER NEAR LWV...WITH 1.3-1.4" EXTENDING BACK TOWARD SW MO
AND SW OH/N KY.  12Z RAOBS/SUBSEQUENT RAP SOUNDINGS SUGGEST FAIRLY
UNSTABLE PROFILES SUPPORTED BY 7C/KM LAPSE RATES IN THE LOW LEVELS
WHICH REDUCE WITH SOME MID-LEVEL WARM/MIXED LAYER ABOVE 6H
REDUCING LAPSE RATES.  REGARDLESS...MLCAPES JUST EXCEEDING 2000
J/KG IN THE WARM SECTOR ARE SUFFICIENT FOR SOLID UPDRAFTS AND
EFFICIENT RAINFALL GENERATION.  

ADDITIONAL SUPPORT WILL BE GAINED THROUGH THE EVENING HOURS AS
RIGHT ENTRANCE REGION DYNAMICS INTENSIFY AS UPSTREAM ENERGY ACROSS
THE UPPER PLAINS AMPLIFIES THE JET AND STRENGTHENS THE GRADIENT
INCREASING  UPPER LEVEL DIVERGENCE/ASCENT TOWARD 02Z. 

CURRENT GOES-E VIS/IR LOOP SHOWS SPOTTED COOLING CONVECTIVE
CLUSTERS ACROSS IL/CENTRAL IN AND -70C TOPPED CLUSTER ACROSS S MO
ATTM.  ISOLATED NEWER CONVECTION HAS BEEN SPROUTING VERY NEAR AND
SOUTH OF THE FRONTAL BOUNDARY ALLOWING FOR MORE SURFACE ROOTED
CONVECTION TO TAP UPPER 60S/70 TDS ACROSS S IL/S IN.  AS ELEVATED
CONVECTIVE CLUSTERS DRIFT SOUTH AND ORGANIZE WITH MORE SURFACE
ROOTED CELLS ALONG THE FRONTAL BOUNDARY...MERGERS AND CELL
TRAINING BECOMES INCREASINGLY LIKELY.  DEEP UNIDIRECTIONAL FLOW
WITH 40KT SWLY DEEP LAYERED MOTIONS GENERALLY PARALLEL TO THE OHIO
RIVER...MAY ALLOW FOR A NARROW CORRIDOR OF TRAINING CONVECTION
ESPECIALLY GIVEN LLJ FROM THE SSW IS 25-30 KTS... SUPPORTS FORWARD
PROPAGATION OF THE CELLS/CLUSTERS TO BE MUCH SLOWER NEAR/BELOW 10
KTS...ALLOWING FOR COMPOUNDED TOTALS.  THIS IS GENERALLY IN LINE
WITH HI-RES CAM GUIDANCE PARTICULARLY THE WRF-NSSL, RECENT
HRRR/HRRR-EXP RUNS AND THE WRF-ARW WHICH SUGGEST 2-3" TOTALS PSBL
IN THE NEXT 6HRS. THIS ALLOWS FOR THE SSEO NEIGHBORHOOD
PROBABILITIES OF EXCEEDING 3HR FFG VALUES TO RANGE BETWEEN 30-50%. 

LIMITING FACTOR TOWARD FLASH FLOODING CONDITIONS IS A LARGE
CONCERN: DRY ANTECEDENT CONDITIONS.  FFG VALUES RANGE FROM
2-2.5/1HR AND 2.5-3"/3HR.  THOUGH CONDITIONS ARE FAVORABLE FOR
TRAINING AND HIGHER RATES GIVEN THE SEASON...FF THREAT SHOULD BE
LIMITED IN COVERAGE UNLESS CELLS SET UP OVER TRADITIONAL SUSPECT
GROUND CONDITIONS SUCH AS URBAN OR FLASH FLOOD PRONE NARROW
GULLIES/CHANNELS ALONG THE OHIO RIVER BLUFFS. 

WPC

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

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

LAT...LON   39438530 39178393 38578428 37958606 37328831 
            36988998 36709193 37339261 37889158 38388993 
            39128768