AWUS01 KWNH 241851
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-250030-

Mesoscale Precipitation Discussion 1186
NWS Weather Prediction Center College Park MD
150 PM EST Tue Dec 24 2024

Areas affected...Northeast Texas...Southwest Arkansas...Northwest
Louisiana...

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

Valid 241850Z - 250030Z

SUMMARY...A low-end threat of flash flooding continues with slow
southeastward drift of frontal zone within favorable training/
back-building regime.

DISCUSSION...18z Surface analysis shows a triple point of digging
cold front and retrograding sliver of dry line near BBD.  A cold
front connects up to a surface wave near Denton before flattening
further into the Red River Valley just north of Texarkana.
GOES-Visible imagery shows the effective warm sector with field of
cu across the majority of E TX, becoming more dense closer to the
coast given slightly higher Tds in the mid 60s and Temps nearing
upper 70s; with the exception of a pocket of low level stratus
that impeded filtered solar radiation across the Hill Country
generally west of HLR/EDC/T20/BEA.  The western Gulf return
moisture flow is solid east of this shallow stratus with 20-25kts
of flow increasing toward 30-35kt nearing the front.  However,
there is a bit of veering that has slightly reduced deep layer
convergence, likely in continued response to the exiting shortwave
across NW AR and an associated diffluence wedge of 3H ascent
across north Texas.  This continues to support isentropic
slantwise ascent across the DFW metro into NE TX in proximity to
the frontal boundary and the convergence is maintaining some
convective cells into northeast TX, though weaker lapse rates due
reduce MUCAPE values below 750 J/kg before reaching SE OK/SW AR
where broader moderate shield precipitation continues.

Recent RADAR mosaic and GOES-E Visible shows some upstream
redevelopment in the core of the peak MLCAPE maxima on the NE side
of the stratus where mid-level SWly flow is providing mid-level
drying and increased lapse rates; near Hamilton county to Bosque
county where values are slowly increasing from 1000 J/kg to 1500
J/kg with further heating.  Moisture flux/pooling in/near the
boundary will aid low-level convergence to support rainfall
production with capability of 1.5"+/hr rates similar to this
morning's bout that could occasionally tick up to 2"/hr IF
prolonged training deepens moisture profile in depth.  As cold
pool generation may overcome due to evaporative cooling; it will
be a storm scale interaction balance and most likely be widely
scattered in nature and limited in duration and therefore
coverage.   Still, this may result in localized 2-3" totals in
less than 2-3 hours.  Unlike earlier this morning, the line of
convection is less likely to track through larger urban, more
hydrophobic ground conditions and rainfall totals are are the
lower end of exceeding the slightly higher FFG in the region.=20
Still, an isolated case of FF still remains possible.

Downstream into far NE TX/SW AR...
Instability is likely to continue to be the limiting factor but
stronger isentropic ascent and with increasingly confluent
850-700mb moisture streams may allow for a broader shield
precipitation to form with occasional embedded convective cores
that ramp up run-off in the short-term. Increasingly deeper
cyclogenesis should also enhanced WAA/moisture flux to the region
that this activity may increase toward end of daylight hours with
rates of 1-1.5"/hr scattered within the deeper unidirectional
steering flow.  Similar 2-3" totals may exist and while not as
flashy in nature given the longer duration; isolated flooding
conditions may evolve though 00z across NE TX into SW AR where
soil saturation values are more average to slightly above average
per NASA SPoRT 0-40cm RSM fields.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9W_4Km_meX7XjyHBudaT4ZRzje7Nt7oiosYUguFSu0i2-PU2qCspQKMl-jCRV2_Ee7vV=
RNcKvVR8VUqy5oX31McLl_A$  for graphic product...

ATTN...WFO...FWD...SHV...

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

LAT...LON   34009441 33639344 32849310 32149370 31639564=20
            30989700 31119823 31889820 32599750 33519600=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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