WPC Met Watch |
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Mesoscale Precipitation Discussion: #0248 (2022) |
(Issued at 1025 AM EDT Wed May 25 2022
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MPD Selection |
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Mesoscale Precipitation Discussion 0248
NWS Weather Prediction Center College Park MD
1025 AM EDT Wed May 25 2022
Areas affected...Southeast & Eastern LA...Central to Southern MS
Concerning...Heavy rainfall...Flash flooding possible
Valid 251425Z - 251955Z
SUMMARY...High rainfall rates may produce instances of flash
flooding this morning.
DISCUSSION...RADAR mosaic imagery highlights a line of
thunderstorms propagating eastward across portions of Louisiana.
Ahead of the line, warm advection storms were developing and
merging with the cold pool driven line, which appeared to slow the
forward motion of the cold pool. The pre-convective airmass
remains very conducive for continued destabilizing even prior to
the outflow boundary, as clearing across Southeast Louisiana
supports RAP MLCAPE of 2500-3000 J/kg. While these values may be
slightly increased due to lingering dry air within the column as
indicated by RAP point soundings ahead of the activity, it is
fairly narrow and supports a deep warm cloud layers exceeding
10,000 feet allowing for a predominance of warm rain processes
within these storms. Available moisture values AoA 1.75" with
solid flux into the convection along the line (as well as
pre-cursory warm sector development) should allow for hourly rain
rates of 2"/hr with occasional best flux cells supporting
localized 2.5"+/hr.
The most recent runs of the HRRR continue to be too slow in
handling the eastward propagation of the line, though the
evolution of the line appears to be better...and as such could
provide confidence for flooding potential further east than
forecast. This would also place the potential for excessive
rainfall rates to align with NASA SPoRT 0-40 cm soil saturation
values around 80% saturated soils in Southeast LA into coastal MS
counties which were affect earlier this morning with localized
2-5" totals. Broadening destabilization of the warm sector
further north into central MS could also support cell mergers as
the squall line moves east and support more isolated/localized
flash flooding even across these areas that have been recently
drier particularly in/near urban settings.
Asherman/Gallina
ATTN...WFO...JAN...LCH...LIX...MOB...
ATTN...RFC...LMRFC...NWC...
LAT...LON 33559057 33118895 30058836 29098880 28888976
29019103 29599167 31149175 32929168
Last Updated: 1025 AM EDT Wed May 25 2022
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