Mesoscale Precipitation Discussion 0570
NWS Weather Prediction Center College Park MD
444 PM EDT Tue Jul 31 2018

Areas affected...South-central Mississippi, Central Alabama

Concerning...Heavy rainfall...Flash flooding likely

Valid 312043Z - 010000Z

Summary...Slow-moving lines of storms will likely continue to
slowly lift northeast from south-central Mississippi into central
Alabama over the next few hours. Ongoing flash flooding near the
Mississippi and Alabama border is likely to continue, and flash
flooding could expand into central Alabama with the heavier rain
over the next few hours. Rain rates of 2-3 in/hr will be possible.

Discussion...KDGX and KBMX radars showed several nearly continuous
arcs of convection extending from McComb, MS to near Birmingham,
AL. These were produced from several converging clusters of
thunderstorms over the past couple hours, and MRMS and KDGX dual
pol radar estimates show a large swath of around 2 in/hr rain
rates from Jones County, MS northeast to Marengo County, AL. The
converging storm clusters in south-central Mississippi may have
stabilized the boundary layer and altered the low-level wind field
(reducing convergence) sufficiently to begin to reduce the
thunderstorm threat in that area over the next few hours. Still,
lingering slow-moving storms and residual instability around the
periphery of the convective cluster could support localized heavy
rainfall and flash flooding. Certainly any ongoing flash flooding
is likely to continue for another hour or two. The greater threat
of heavy rainfall is likely to shift into central Alabama over the
next few hours. Greater instability exists to the northeast of the
current convective lines (2000 j/kg MLCAPE) and radar trends show
the lines slowly lifting northeast. The 19Z HRRR shows its QPF max
in the 21-00Z time frame between Meridian and Birmingham, which
seems reasonable given the current radar trends. This may allow
new flash flooding to develop in the next few hours northeast into
central Alabama and the Birmingham metro area.

Lamers

ATTN...WFO...BMX...JAN...LIX...MOB...

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

LAT...LON   33758722 33638564 32358596 31528828 30659016
            30949080 32408991