Weather Prediction Center issues Mesoscale Precipitation Discussion #1163 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE196
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Mesoscale Precipitation Discussion 1163
NWS Weather Prediction Center College Park MD
227 PM EDT Mon Oct 06 2025
Areas affected...Southeast Louisiana...Mississippi...Coastal
Alabama...
Concerning...Heavy rainfall...Flash flooding possible
Valid 061830Z - 070000Z
SUMMARY...Reinvigoration of convective bands will have similar
potential for back-building and short-term training resulting in
2-4" totals given 2-2.5"/hr rates. Localized flash flooding
remains possible through the evening.
DISCUSSION...GOES-E GeoColor Visible imagery shows well defined
surface to mid-level circulation along the LA/AR border with broad
warm advective regime along the eastern hemisphere across much of
MS into SE LA. Surface analysis shows some weak reflection in
pressures further south than the wind circulation along the
border, but a defined frontal zone extend along the MS River into
the Atchafalaya Swamps of south-central LA...east of it higher
theta-E air with increasing temperature spreads into the 80s over
Tds in the mid to upper 70s. Early morning south to north
convective line exists along the eastern side of the warm sector
before low to mid-level clouds have been keeping temps in near the
Tds north of the warm front from GLH to north of JAN to E of HBG
and south to Mobile Bay. Surface to boundary layer moisture
pooling along the warm front intersects with SSW LLJ across SE LA
into central MS where Total PWat values are well above average in
the 2.25"+ range. The confluence of the conveyor belts has
resulted in strong moisture flux convergence generally coincident
or just north of the expanding instability wedge. MLCAPEs are
increasing from 1000 to 2000 J/kg from the warm front southward to
the Gulf; providing the strength for vertical development.
Recent GOES-E Vis/IR loops along with regional RADAR mosaic
denoted leading edge of old outflow and intersection of the warm
front has seen increased convective vigor and vertical depth in
the last hour or so. While winds are generally 20-25kts through
depth, it is the strong confluence with height that present the
stronger convergence to tap the unstable air. Moisture flux of
the high moisture will result in increasing rain-rates of
2-2.5"/hr. Steering flow will allow for south to north training,
though momentum and some weak cold pool generation should allow
for some eastward propagation to limit overall duration. Spots of
2-4" are probable and may result in localized flash flooding
concerns.
Additionally, GOES-E WV suite denotes a weak inflection along the
cold front near the Gulf coast lifting northeastward within the
larger shortwave lifting north through the MS Valley, this is
indicative of some increased low-level jet streak to support
upstream back-building. In addition, while not in the core of the
warm conveyor belt, convergence along the cold front toward the
triple-point could see even slower, but shallower thunderstorms
capable of intense rainfall as well. The potential of upstream
development in proximity to the front could expose areas of
lowered FFG from this morning's thunderstorm activity and
reaggravate flooding concerns there as well. As such, have
expanded the MPD area of concern to the cold front to encompass
this lower confidence, wider scattered activity and flash flood
potential.
Gallina
...Please see www.wpc.ncep.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...MEG...MOB...
ATTN...RFC...ALR...ORN...NWC...
LAT...LON 34698960 34158873 32378849 31398795 30508763
30178795 30268891 30088985 30109055 30369132
31569090 32719080 33569100 34289043
Source:
Weather Prediction Center issues Mesoscale Precipitation Discussion #1163 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE---------------
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