Mesoscale Precipitation Discussion 0099
NWS Weather Prediction Center College Park MD
312 AM EDT Mon Mar 31 2025

Areas affected...Northeast LA...Southern AR....Northern MS...

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

Valid 310710Z - 311200Z

SUMMARY...Favorable training profile for strong thunderstorms
capable of 2"+/hr rates.  Localized totals of 2-4" in 2-3hrs pose
possible localized flash flooding over the next few hours.

DISCUSSION...GOES-E 10.3um and regional RADAR mosaic has shown
consistent strong development that has maintained itself across S
AR, starting to spread downstream into NW MS, with additional
upstream overshooting tops breaking through the cirrus canopy over
north-central LA.  GOES-E WV and AMV suite shows a strong speed
max starting to round the southeast quadrant of a larger scale
trof through the Ozarks providing solid divergence aloft.  RAP
forecasts are expected for the jet to further enhance the
downstream right entrance region across the central MS Valley
maintaining solid divergence across the lower Delta Region into N
MS over the next few hours.   At the surface, a slowly forming
surface low along a stalled portion of the main front has locally
backed surface to boundary layer flow tapping enhanced moisture
and unstable airmass out of the MS Valley.  Tds in the low 70s and
MLCAPE to 1500 J/kg combined with the convergence downstream of
the surface low will maintain inflow/flux convergence to further
expand convective development over the next few hours.  Veering
mid-level flow above the boundary layer is also providing
850-700mb moisture flux from a pool of enhanced moisture upstream
to increase rainfall efficiency and likely limit cold pool
development.

Deep layer steering is also generally parallel to the boundary to
support moderately lengthy axis for training over the next few
hours.  As such, a streak of enhanced rainfall with 2-4" totals
should extend from S AR into northern MS.  This aligns with a
localized minimum in FFG values along the river and northeastward
where 1/3hr FFG values of 1.5-2" & 2-3" have a solid potential of
been exceeded in spots along the training axis.  In the longer
term maintenance of the line of convection will be determined on
upstream development over central LA and points south.  If
clusters develop, inflow/flux of moisture/unstable air is likely
to be disrupted, but until then there is a good possibility of an
incident or two of localized flash flooding through early morning.

Gallina

ATTN...WFO...JAN...LZK...MEG...SHV...

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

LAT...LON   34858901 34268829 33388846 32878936 32679035
            32589159 32609252 32819306 33349308 34369101
            34729014