Mesoscale Precipitation Discussion 0808
NWS Weather Prediction Center College Park MD
902 PM EDT Sat Sep 08 2018

Areas affected...Eastern AR...Western TN... Northern MS... Ext
South Central KY....

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

Valid 090100Z - 090630Z

SUMMARY...Moist confluent flow, should support training and cell
mergers capable of producing possible flash flooding conditions.

DISCUSSION...Regional RADAR reflectivity mosaic denotes a weak low
to mid-level twist across central AR with showers/thunderstorms
along the trof across western TN into south central KY connected
to the tail end of the remnants of Gordon.  VWP network suggests
strongly confluent flow across W TN before being squeezed/severed
from the northern wave across central KY.  Instability is
generally weak and reducing as the ongoing convection uses up the
remaining fuel.  So in the short-term storms will continue to
fairly efficient given mean mixing ratios in the 16 kg/kg range
and total PWATs across the 2.4" near the AR wave reducing to
1.8-1.9" across KY, with continued cycling/overshooting tops in
10.3um reaching -65C, expect rates over 2-2.5"/hr with these
cells.  This combined with confluent flow, support mergers and
some training tracks across west central to north central TN. 
Still, with loss of daytime heating, cells should begin to wane
with time, reducing in rainfall intensity and replaced by more
gentle rates and more isolated deeper cells.

The greatest risk for flash flooding in the short term exits in
metro Memphis where multiple mergers and deep convection near
metro Memphis has the potential to produce 2-4" quickly.  
Isolated totals of 5" are possible as indicated by recent HRRR
runs.   Ground conditions are quite saturated across AR, where FFG
values remain in the 1.5-2" range in 1hr and below 2.5"/3hrs. 
Further east into central TN, where the signal for greatest
confluence/rain totals are expected (MEM to MKL), recent drier
conditions can support a bit higher magnitudes... and as such
flash flooding is considered possible through the area of concern
though more likely in the Memphis metro given current trends for
mergers/training. 

Gallina

ATTN...WFO...LMK...LZK...MEG...OHX...PAH...

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

LAT...LON   36978724 36798635 35828661 34598922 34169084
            33969174 34119270 34999267 35849104 36218974