AWUS01 KWNH 261856
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-270100-

Mesoscale Precipitation Discussion 1193
NWS Weather Prediction Center College Park MD
156 PM EST Thu Dec 26 2024

Areas affected...Northeast TX...Southeast OK...Far Southwest AR...

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

Valid 261900Z - 270100Z

SUMMARY...Reducing instability, rainfall efficiency; but slower
moving cells with some training pose spots of 2-3" and widely
scattered possible flash flooding through evening.

DISCUSSION...The window for excessive rainfall inducing localized
flash flooding is starting to close due to multiple factors; one
being convection moving into areas of higher FFG, though still
equally saturated in the 0-40 cm layer with NASA Sport RSM still
in the 60-70% range.  The second is reducing moisture flux and
available instability.  Yet, a training steering profile still
remains as well as potential for stationary cells near the
pivoting deep layer cyclone over Northern Texas toward 00z.

Currently, regional RADAR mosaic and GOES-E suite of imagery show
the decaying convection along the effective 850-700mb warm front
across NW LA/SW AR angling back to the developing deep layer pivot
of the cyclone over the central Red River Valley between North and
Northwest Texas.  Strong height-falls as the upper-level jet and
5H trough swing more negative tilt across central to northeast
Texas; the effective 850mb cold front is aligning to the surface
and is pressing much faster eastward to the south.  A mid-level
dry slot/descent channel is starting to pinch in proximity to
Falls, Robertson and Bell county and the LLJ is starting to take a
more branched appearance as the confluent flow increases
convective activity along the trailing convergent southwesterly
flow and effectively severs the best deep layer moisture transport
along and ahead of the effective 850mb advancing front.=20

Currently, the window is still open and  MUCAPE values 750 J/kg
nosing toward 1000 J/kg are still within access and ascend through
the western branch of the TROWAL to maintain/promote convective
activity across the Heart of Texas region.  The southerly backing
30kt flow is supporting 1.25" total PWats mainly below 700mb to
providing solid flux convergence for efficient rainfall production
for the next few hours with rates of 1-1.25" slowly diminishing
with time.   Deep layer steering at the nose/left rotor of the
developing dry slot may allow for cells to angle sufficiently for
some short-term SW to NE training from Freestone/Navarro county
region to Red River/Cass counties over the next 4-6 hours.  As the
dry slot severs the connection rates will drop below 1"/hr and
overall totals will reduce to less than the rising FFG values in
far NE TX, reducing the potential for low-end flash flooding
conditions.

A secondary risk may start to occur near the pivot of the deep
layer cyclone as it crosses North Texas toward 00z.  Steepening
lapse rates and remaining modest pooled moisture and convergent
flow along the southeast quadrant may spark a few narrow core
convective cells.  Deep layer steering will be near zero near the
center of the low, allowing for Subtle Heavy Rainfall Signature
(SHaRS) events with 1-1.5"/hr rates falling over areas having
recently experienced prolonged moderate shield precipitation
across the Red River Valley and across into S OK.  These would be
very spotty in nature, but the intensity of the rates in such a
small area could pose a localized flash flooding risk as well.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6UeAJSEdlBDof7NCT1FAGCfMmd71AcYjg4AgLFxxQkSypyZ3Uumopuv5xMQCBmxZvgts=
T2blZsW2fz5MmAwGwxQv8HU$  for graphic product...

ATTN...WFO...FWD...OUN...SHV...TSA...

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

LAT...LON   34419525 34109433 33619364 32979395 32289460=20
            31229645 32409692 33729715 34299646=20

=3D =3D =3D
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