Mesoscale Precipitation Discussion 1071
NWS Weather Prediction Center College Park MD
1215 PM EST Thu Dec 27 2018

Areas affected...Louisiana into Central MS

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

Valid 271714Z - 272314Z

Summary...A intense line of convection will slow its forward
movement increasing the risk for flash flooding, hourly rates
exceeding 2", and totals through 5 pm CST of 3-4". 

Discussion...As of 17z, a well defined line of convection
continues across portions of west-central Mississippi down through
central Louisiana. This activity is being supported by broad upper
level divergence associated with a closed low over Kansas. A plume
of anomalously high moisture characterized by PWATS of 1.5 to 1.6"
all within a belt of strong 850 mb moisture transport exists ahead
of this low, in place over LA/MS. Finally, MLCAPE of 500 J/kg
extends as far north as central MS, which is expected to remain in
place through the afternoon, enhancing the risk for intense
rainfall rates. Overall, the environment is also supportive of
training convection, with the mean flow aligned parallel to storm
motions, especially by this afternoon where 850 mb flow is
expected to be 50-60 kts.

Through 23z, this line of storms is expected to run out ahead of
the best forcing/lift that is associated with the mid/upper level
low across the Plains. This should allow for a slowing trend in
the forward movement of the line, especially across Louisiana and
south-central Mississippi. The line is also likely to become less
north-south oriented, taking on some west-east components, as it
aligns itself with the mean 850 mb flow.

Recent observations and radar imagery show hourly rates exceeding
2" across portions of west-central MS and south-central LA, and as
the line slows down, there will be an increased risk for totals to
exceed 3-4" in places. The intense rates combined with the longer
duration will make flash flooding more likely as we head into the
afternoon hours.

Taylor

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

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

LAT...LON   33118987 33098836 32478808 31478856 29759008
            29489120 29649277 30759179 31579105 31869077
            32629003