Mesoscale Precipitation Discussion 0607
NWS Weather Prediction Center College Park MD
225 PM EDT Tue Aug 07 2018

Areas affected...Portions of the Mid-South states

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

Valid 071824Z - 080024Z

Summary...A developing line of heavy thunderstorms will continue
to progress east from the Ozarks to the Mississippi River through
the rest of the afternoon with heavy prefrontal development making
for an isolated flash flood threat over the Mid-South.

Discussion...Latest radar/satellite trends indicate increasing
shower/thunderstorm coverage across southeast Missouri and
southern Illinois which is ahead of a line of thunderstorms over
southern Missouri/northern Arkansas (over the north-central Ozarks
at 18Z). This activity is ahead of a deep trough axis over the
east-central Great Plains.

Southwesterly flow ahead of the trough has allowed dewpoints in
the low to mid 70s and precipitable water values of 1.75-2 inches
which is a 1.5 standardized anomaly over normal. Heavy downpours
are expected within the showers/storms.

12Z CAMs (ARW/ARW2/NMMB) focus 18-00Z precipitation around St.
Louis. However, mid-level clouds on GOES-16 imagery across central
MO and radar trends suggest the threat is farther south in MO and
around the mid-Mississippi Valley. Rain rates of 2 in/hr have
already been estimated by NEXRAD which is expected to continue.
Flash flood guidance is high (2-3in/hr) given only scattered
precipitation over the past week and below normal precipitation
for the past month. A loss of terrain as this activity moves east
is also a detriment to flash flood potential. Therefore, flash
flooding is expected to be isolated in this area this afternoon
particularly as the line crosses areas impacted by the prefrontal
thunderstorms and is considered possible.

Jackson

ATTN...WFO...LSX...LZK...MEG...PAH...SGF...

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

LAT...LON   38139059 37638794 36578820 35699107 35609275
            35999251 36639175 37479127