Graphic for MPD #0778

MESOSCALE PRECIPITATION DISCUSSION 0778
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
831 AM EDT FRI SEP 01 2017

AREAS AFFECTED...CENTRAL/EASTERN KY...FAR NORTHERN TN

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

VALID 011230Z - 011830Z

SUMMARY...HEAVY RAINS WILL CONTINUE TO FOSTER CONCERNS FOR FLASH
FLOODING THROUGH THE LATE-MORNING AND EARLY-AFTERNOON HOURS.

DISCUSSION...T.D. HARVEY CLOSE TO BEING DECLARED EXTRATROPICAL AS
THE LOW CENTER ASSOCIATED WITH HARVEY COMPLETELY MERGES WITH A
FRONTAL ZONE OVER THE TN VALLEY. A WELL-DEFINED JET-ENHANCED
DRY-SLOT CAN ALSO BE SEEN WRAPPING NORTHEAST AROUND THE EASTERN
FLANK OF HARVEY AND SUGGESTIVE OF A SYSTEM TRANSITIONING TO A
BAROCLINIC LOW.

THE HEAVIEST RAINFALL IS NORTH OF THE LOW CENTER AND IS ASSOCIATED
WITH STRONG ISENTROPIC LIFT AND FRONTOGENETICALLY ENHANCED
FORCING. HOWEVER...THERE STILL IS AN AREA OF STRONGLY FORCED
CONVECTION IN A VERY NARROW FASHION JUST NORTH AND NORTHEAST OF
THE LOW CENTER WHERE THERE IS SOME VERY STRONG SURFACE CONVERGENCE
AND AT LEAST SOME VERY MODEST INSTABILITY TRANSPORT. RAINFALL
RATES WITHIN THIS NARROW CONVECTIVE BAND OVER SOUTHERN KY AND FAR
NORTH TN HAVE BEEN ON THE ORDER OF 1.5 INCHES/HR. SOME OF THESE
AREAS HAVE ALREADY SEEN AS MUCH AS 6 TO 9 INCHES OF RAIN...AND ANY
ADDITIONAL HEAVY RAINFALL WILL FOSTER ENHANCED RUNOFF AND FLASH
FLOODING.

THE LATEST HRRR GUIDANCE SUPPORTS SOME ADDITIONAL 2 TO 4 INCHES
RAINFALL TOTALS THROUGH 18Z...WHICH SEEMS REASONABLE BASED ON THE
LATEST RADAR/SATELLITE TRENDS. THIS IS ALSO GENERALLY SUPPORTED BY
A CONSENSUS OF THE 00Z HIRES ARW/NMMB SOLUTIONS. WILL CONTINUE TO
MONITOR.

ORRISON

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

ATTN...RFC...OHRFC...

LAT...LON   38648432 38438320 37908277 37358309 36898447
            36368513 36288580 36528612 36748689 37338706
            37758673 38278577


Last Updated: 831 AM EDT FRI SEP 01 2017