AWUS01 KWNH 101020
FFGMPD
ALZ000-MSZ000-LAZ000-101615-

Mesoscale Precipitation Discussion 1171
NWS Weather Prediction Center College Park MD
519 AM EST Tue Dec 10 2024

Areas affected...southern LA into south-central MS and western AL

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

Valid 101018Z - 101615Z

SUMMARY...Showers and embedded thunderstorms will increase this
morning across southern LA/MS/AL. Rainfall coverage and intensity
should increase through 16Z and areas of training will be capable
of producing 1-2 in/hr rainfall rates. Flash flooding will be
possible, especially where overlap occurs with rainfall from Monday.

DISCUSSION...Radar and GOES East satellite imagery from 10Z showed
a SW to NE oriented zone of widely scattered showers with embedded
thunderstorms translating toward the east across southern LA into
south-central MS. These showers were located along a near surface
convergence axis located out ahead of a cold front, which draped
from southern AR into southeastern TX. MLCAPE was fairly weak over
LA/MS (500-1000 J/kg per 10Z SPC mesoanalysis data) but shower
activity was located just to the west of an axis of precipitable
water values that contained 1.5 to 1.7 inches.

As broad lift begins to overspread the Lower MS Valley, out ahead
of a large, positively tilted, upper trough axis over the
Southwest, the coverage and intensity of showers/thunderstorms
along the eastward progressing low level convergence axis will
increase. This should also be true as the convergence axis reaches
higher precipitable water values to the east along with forecasts
of increasing instability with daytime heating. An upper level jet
max over the eastern TX/OK border, with GOES East DMVs having
sampled 120-130 kt between 07-08Z near 250 mb, is expected to
continue to increase in magnitude as it translates downstream
toward the MS River through the morning. Locations within the
right-entrance region of this upper jet max are expected to see
enhanced lift through late morning. Mean steering flow from the
southwest will parallel the axis of forcing allowing for training
of heavy rain at times with 1-2 in/hr becoming more likely later
this morning as the axis of heavy rain shifts east.

While expected rainfall through 16Z is likely to fall primarily to
the north of a stripe of heavy rain (2 to 5 inches) which fell
across portions of the central Gulf Coast on Monday, localized
convective development near the Gulf Coast...or closer to the
source of higher instability...could overlap with these more
hydrologically sensitive areas to generate flash flooding. Farther
north, any areas of flash flooding that develop should remain
localized atop low lying and/or urban areas.

Otto

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

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

LAT...LON   33068836 32588751 31838799 30219007 29529181 
            29679238 30139264 31089168 32638948 

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