AWUS01 KWNH 281705
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-282230-

Mesoscale Precipitation Discussion 1201
NWS Weather Prediction Center College Park MD
1204 PM EST Sat Dec 28 2024

Areas affected...eastern TX, northern LA, southern AR,
northwestern MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 281700Z - 282230Z

SUMMARY...Areas of training heavy rain, with rates of 1-3 in/hr,
will affect portions of eastern TX into northern LA, southern AR
and perhaps far northwestern MS through 22Z. Rainfall totals of
3-5 inches in 2-3 hours will be possible across a SW to NE
oriented axis, overlapping TX/LA/AR.

DISCUSSION...Regional radar imagery at 17Z showed scattered to
widespread thunderstorms from the AR/LA border into northeastern
TX. Convection extended roughly near/north of a stationary front
which was analyzed WSW from the MS/AR border into eastern TX at
17Z. Convection transitioned into a QLCS with southeastward bowing
observed across I-20 in eastern TX. Meanwhile, an upstream NNE to
SSW axis of thunderstorms was pressing east along I-35 between ACT
and SAT, located just ahead of a pre-frontal trough/dryline. 30-40
kt of SW 925-850 mb flow was advecting moisture northward through
southeastern TX into the stationary front which marked a gradient
in MLCAPE with roughly 500-1500 J/kg along the boundary via 16Z
SPC mesoanalysis data.

As a potent mid-level shortwave continues to advance east from
central TX today, downstream forcing will increase as an upper
level jet max becomes better defined over eastern OK, placing
right-entrance ascent over the Arklatex to Lower MS Valley. Low
level winds may also increase a little more into the afternoon
ahead of the upper trough axis. Thunderstorms are expected to
continue to expand in coverage ahead of the advancing convective
line near I-35 with low level convergence near the stationary
front aligning with mean SW steering flow to support
training/repeating cores of heavy rain. PWAT coverage of 1.5
inches and greater is forecast to expand across the region,
coupled with more than sufficient instability and favorable shear
to promote organized cells. Thunderstorms will be capable of
producing 1 to 3 in/hr rainfall rates due to training and
repeating rounds could amount to 3-5 inches of rain in a 2 to 3
hour period.

The greatest concern for training and the heaviest rainfall totals
through 22Z will be in the vicinity of the stationary front from
northeastern TX into northern LA/southern AR and perhaps far
northwestern MS. Farther south, while the convective line near
I-35 is likely to remain progressive from west to east, additional
development ahead of the line and periods of short term training
within the convective axis may still promote a threat for flash
flooding across portions of southeastern TX into western LA.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4i5B_CGCd0spZ74-7xxxyMPvLmBC7c-caEj4poEVxog-A1lcfgRu45FBPALHA4_OinGV=
Q7HFihBaK-K5Mr1ZVIIl3wA$  for graphic product...

ATTN...WFO...FWD...HGX...JAN...LCH...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON   34599115 34399049 33749063 32799145 31879208=20
            30719287 30099476 30589647 31169716 31819719=20
            32369670 32679535 33579389 34119247=20

=3D =3D =3D
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