Mesoscale Precipitation Discussion 0301
NWS Weather Prediction Center College Park MD
1121 AM EDT Wed May 21 2025

Areas affected...Southern Louisiana...Far Upper Texas Coast...

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

Valid 211520Z - 212030Z

SUMMARY...Highly efficient, slow moving thunderstorms with
additional training and upstream development may result in
localized 2-3"/hr rates and rapid inundation flooding is possible.

DISCUSSION...An extremely moist deep layer profile exists along
the frontal zone that is becoming coincident with the LA/Upper TX
coastline.  Total PWat values are over 2.25" with some suggestion
of 2.5" values embedded along it.  Initial convection has further
sharpened the insentropic slope with 10-15kts of northeasterly
flow opposed by 5-10 kts of due southerly flow across the front. 
Upper-level broad right entrance to 90kt 3H jet across
east-central TX into northern LA is providing solid upper level
divergence, which the convection is likely further enhancing to
support additional development/organization over the next few
hours.  Given moisture, rates of 2.5-3"/hr are likely with the
cores of the cells, which can be confirmed by last hour at LFT as
well as surrounding observations near UofL-Layfette of 3" in the
last hour as well...supporting localized rapid inundation
potential.  

While the gradient of deep layer moisture/unstable environment
basically aligns from I-10 to the coast, the steering flow is
ideally orientened parallel to the front and moisture/instability
graident to allow for favorable training environment.  So given
broad southerly flow/isentropic ascent convergence there are
additional cells in the Upper TX coastal region with further
congested cu west of Galveston Bay, hinting at continued expansion
potential along/upstream for localized training environment
throughout the rest of the morning/early afternoon hours from
south of Houston to New Orleans.  While Hi-Res CAMs suggest some
dry air mixing to allow for southward propagation (cold pool
generation), RADAR trends have not be aligned with this evolution
but the risk should still remain along/south of I-10.

Gallina	

ATTN...WFO...HGX...LCH...LIX...

ATTN...RFC...FWR...ORN...NWC...

LAT...LON   30649023 30058986 29649004 29479139 29499251
            29629299 29699347 29059539 29529554 30169398
            30349339 30629173