Mesoscale Precipitation Discussion 0090
NWS Weather Prediction Center College Park MD
523 PM EST Fri Mar 08 2024

Areas affected...southern Mississippi, southern Alabama,
southeastern Louisiana

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

Valid 082222Z - 090422Z

Summary...Flash flood potential continues as an MCS develops
southeastward across the discussion area through 04Z.

Discussion...The combination of earlier convection and light 850mb
northerly flow (per RAP analyses and high-res model guidance) has
allowed for an extensive front/outflow boundary to shift southward
across central Mississippi and portions of southwestern Alabama
and is generally located from west of Montgomery, AL to near
Hattiesburg and McComb, MS.  Earlier, convection focused along
this boundary resulted in widespread 3-5 inch rainfall totals
along the I-20 corridor in Mississippi along with several reports
of excessive runoff and flooding.  Recent radar and objective
analyses indicate general storm motions that have allowed for
training (and 1.5-2 inch/hr rain rates) in southern Mississippi
over the past hour, although the southward movement of the
front/outflow and west-southwesterly flow aloft has undercut
deeper convection especially in southern Mississippi.  This
scenario has tempered the longevity of rainfall rates at times,
although areas of 2 inch/hr rain rates continue to persist for at
least an hour near the outflow where cells can remain at or close
to surface based while maturing and becoming persistent.

The ongoing scenario for flash flooding is expected to continue
through 04Z, although a slow south and southeastward translation
is expected to continue.  This should enable training and areas of
~2 inch/hr rain rates to develop especially from southeastern
Louisiana into southern Alabama through the evening along and
ahead of the outflow boundary.  While FFGs increase into the 3
inch/hr range with southward extent, at least local impacts are
expected where heavier rainfall and/or training can impact
low-lying or urbanized areas.  Additional rainfall totals are
expected to reach 2-3.5 inches especially where training is most
pronounced.  Lastly, destabilization is expected across southern
Alabama through the evening which should continue to support areas
of deep convection and training.

Cook

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

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

LAT...LON   32538668 32008615 30898637 30378726 30048884
            29528978 29419072 30399161 31069107 31729037
            32078953 32478734