Mesoscale Precipitation Discussion 0883
NWS Weather Prediction Center College Park MD
518 PM EDT Sat Sep 22 2018

Areas affected...Northern MS...Far Northwest AL...Central
TN...Southeast KY...Southwest VA

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

Valid 222115Z - 230200Z

Summary...Showers and thunderstorms with heavy rainfall rates will
tend to expand a bit more in coverage over the next few hours.
Some flash flooding is possible.

Discussion...The latest GOES-16 visible satellite imagery has been
showing an expansion of convective tops from northern MS
northeastward across central TN, southeast KY, and far southwest
VA. The activity has been forming along a frontal zone and within
an axis of instability with MLCAPE values of as much as 1000 to
1500 j/kg. Additionally, there is some modest right-entrance
region jet dynamics in place over the region which is being
facilitated by the northeast advance of a shortwave trough moving
into the OH Valley.

Rainfall rates are expected to be rather heavy given PWATs on the
order of 1.75 to 2 inches which is a solid 2 standard deviations
above normal, and the latest HRRR-tle probabilistic output does
suggest hourly rainfall amounts of as much as 2 inches.

The thunderstorm activity may tend to organize a bit further over
the next couple of hours before the instability pool begins to
wane, and actually the latest HRRR guidance does favor some
localized pockets of 3 to 4 inch rainfall amounts going through
mid-evening. Some flash flooding will be possible as a result.

Orrison

ATTN...WFO...HUN...JAN...JKL...LMK...MEG...MRX...OHX...RLX...
RNK...

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

LAT...LON   37458263 37418174 37288098 37078063 36858089
            36768155 36688245 36418384 35908518 35478601
            34828743 33698916 33588971 33899004 34249006
            34858958 35428881 36178728 36688574 37138442
            37358361