MESOSCALE PRECIPITATION DISCUSSION 0197
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 AM EDT WED MAY 11 2016
AREAS AFFECTED...SOUTH-CENTRAL KY & CENTRAL TN
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 110757Z - 111157Z
SUMMARY...THERE HAS BEEN A RECENT REJUVENATION OF CONVECTION
ACROSS CENTRAL TN. ANOTHER 3-5" IS POSSIBLE LOCALLY, WHICH COULD
LEAD TO ADDITIONAL FLASH FLOODING.
DISCUSSION...THE FORMER DEW POINT GRADIENT HAS MANIFESTED ITSELF
INTO A THERMAL DISCONTINUITY ACROSS WEST-CENTRAL TN, WITH A WEAK
OUTFLOW BOUNDARY ACROSS CENTRAL TN. CONVERGENT FLOW AT 850 HPA
ALSO LIES NEAR THE WEAK OUTFLOW BOUNDARY. THE AREA REMAINS
DIVERGENT ALOFT NEAR THE SOUTH SIDE OF AN UPPER VORTEX ACROSS
NORTHWEST OH, WITH A JET STREAK APPROACHING THE AREA FROM OK/MO,
PER RECENT SATELLITE IMAGERY. MUCAPES OF 1000-2000 J/KG REMAIN
WEST OF THE REGION PER SPC MESOANALYSES, WHICH ARE BEING WHISKED
INTO THE REGION BY 850 HPA INFLOW OF 40 KTS PER VAD WIND PROFILES.
CELL MOTION WITHIN THE ORGANIZED BAND REMAINS EAST-SOUTHEAST AT
20-25 KTS, A COMPROMISE BETWEEN FORWARD PROPAGATING CONVECTIVE
VECTORS AND THE 1000-500 HPA THICKNESS PATTERN.
NORTHWEST-SOUTHEAST THUNDERSTORM BANDS LIKE THIS HAVE BEEN TRICKY
TO FORECAST OVER THE YEARS WITHIN THIS SORT OF SYNOPTIC PATTERN.
PRECIPITABLE WATER VALUES NEAR 1.5" SUPPORT HOURLY RAIN RATES UP
TO 1.75", WHICH COULD BE HIGHER IF A LONG ENOUGH TRAINING BAND
DEVELOPS OR CELL MERGERS OCCUR, SUCH AS WHAT HAPPENED AROUND THE
NASHVILLE SUBURBS EARLIER. AFTER 10Z, RAP MASS FIELDS INDICATE A
WEAKENING OF THE LOW-LEVEL INFLOW, PRESUMABLY DUE TO THE EASTWARD
MOTION/PULLING AWAY OF THE UPPER VORTEX OVER OH. HOWEVER, THE
MESOSCALE/CAM GUIDANCE SUGGESTS ANOTHER 3-5" OF RAIN IS POSSIBLE
LOCALLY, WHICH COULD OCCUR QUICKLY AND GENERALLY PRIOR TO 12Z.
UNCERTAINTY KEEPS THE CATEGORY OF THIS MPD A POSSIBLE.
ROTH
ATTN...WFO...JKL...LMK...MRX...OHX...PAH...
ATTN...RFC...LMRFC...OHRFC...
LAT...LON 37408675 37238574 36718495 35788439 35298485
35268575 36188697 36688736 37158748
Last Updated: 358 AM EDT WED MAY 11 2016