AWUS01 KWNH 281028
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-281625-

Mesoscale Precipitation Discussion 1200
NWS Weather Prediction Center College Park MD
525 AM EST Sat Dec 28 2024

Areas affected...Northern and Eastern TX...Northern LA...Southern
AR...Western MS

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

Valid 281025Z - 281625Z

SUMMARY...Showers and thunderstorms will begin to rapidly develop
and expand in coverage by mid to late morning. Heavy rainfall
rates and wet antecedent conditions will promote increasing
concerns for flash flooding with time.

DISCUSSION...The early morning GOES-E Airmass RGB satellite
imagery shows a mid to upper-level shortwave trough amplifying
east-southeastward out of the southern High Plains and advancing
toward the Red River Valley of the South. Increasingly divergent
flow aloft and strengthening shear parameters interacting with the
poleward transport of moisture and instability up across central
and eastern TX will set the stage for rapidly developing clusters
of strong thunderstorms in the 12Z to 15Z time frame across areas
of north-central to northeast TX, with development also then
taking place farther east in close proximity to a warm front over
into areas of northern LA, southern AR and possibly western MS.

This warm front will be an important focus for convection going
toward midday as a strengthening and increasingly convergent
southerly low-level jet reaches 30 to 40+ kts in response to
surface low pressure deepening upstream across north-central TX.
Already there is as much as 1500 to 2500 J/kg of MLCAPE noted over
south-central to southeast TX and southern LA which will be
lifting north over the next several hours. The convection should
rather quickly become organized with combinations of multicell and
supercell thunderstorms evolving and growing upscale in a west to
east fashion as stronger upstream forcing arrives in conjunction
with the strengthening low-level jet.

PWs increasing to 1.25 to 1.5 inches coupled with the instability
and strengthening shear will likely favor the stronger storms by
late morning producing rainfall rates as high as 1 to 2
inches/hour, and there will likely be increasing concerns for some
cell-merger activity and cell-training near the aforementioned
warm front. Warm sector convection farther south over areas of
eastern TX will also begin to initiate and evolve by late morning
which will be capable of producing enhanced rainfall rates.

Some rainfall totals of 2 to 4 inches will be possible with the
morning activity, and with the antecedent conditions quite wet
with elevated streamflows across much of eastern TX and into the
Arklatex region, these rainfall amounts are expected to increase
the threat of flash flooding. This will include an urban flash
flood threat from near the Dallas-Fort Worth metropolitan area
eastward over toward Shreveport. More organized coverage of strong
thunderstorms (with notable severe weather concerns) along with
heavy rainfall and flash flooding will evolve beyond this period,
and expect more MPDs to be issued accordingly.

Orrison

ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LZK...OUN...SHV...TSA...

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

LAT...LON   34119456 34059309 33929136 33259058 32489072 
            31899145 31649230 31249413 30429588 30309690 
            30749739 31419742 31839807 32239820 33089740 
            33699638 33979555 
$$
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