Mesoscale Precipitation Discussion 1010
NWS Weather Prediction Center College Park MD
913 PM EST Mon Nov 05 2018

Areas affected...Middle TN into Central Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 060213Z - 060813Z

Summary...A few lines of thunderstorms tracking across portions of
the Tennessee and lower Ohio Valley will have the potential to
produce flash flooding into the early overnight hours.

Discussion...Latest GOES-East water vapor imagery shows a
well-defined shortwave across the central US. Favorable upper
level divergence exists across portions of the lower OH and TN
Valleys where a tongue of higher moisture (PWATs 1.5"+) have
advected north/northeastward. Surface instability axis exists as
far north as southwest TN but elevated instability of 500-1000
J/kg extends up into western TN into south-central KY.

Radar returns from around the area show a couple lines of
thunderstorms organizing, where 1-hr radar estimated rates have
picked up to 1-1.5". Surface observations from western TN show
hourly totals as high as 1.2" already within the line of
convection.

Over the next several hours, the axis of best instability is
expected to be squeezed as far north as south-central KY,
coinciding with the highest PWAT axis (2-2.5 SD above the mean)
and best upper level forcing arrival. With near unidirectional
flow and an increasing low-level jet (850 mb flow increasing to
60+ kts), this should favor training convection and potential for
intense rainfall rates as high as 2"/hr.

Overall the hi-res models are consistent in the next 6 hours
showing the heaviest rainfall likely to fall from middle TN into
south-central KY and portions of the southern Bluegrass region.
Totals of 2-3" with locally higher amounts up to 4" will be
possible.

Mitigating factors for more widespread flood issues is the
slightly higher FFG (1-hr FFG around 2") across TN and southern
KY. However , lower values of 1-1.5" in 1-hr are across portions
of the Bluegrass of KY and eastern KY. Nuisance flooding in urban
areas, poor drainage locations, and other low-water crossings will
be most susceptible to flooding into the early overnight hours. 

Taylor

ATTN...WFO...JKL...LMK...MEG...OHX...PAH...

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

LAT...LON   38338423 37618374 36408530 35298754 35378896
            36048874 37158699 38228558