356
AWUS01 KWNH 051207
FFGMPD
TXZ000-051730-

Mesoscale Precipitation Discussion 0399
NWS Weather Prediction Center College Park MD
807 AM EDT Wed Jun 05 2024

Areas affected...Heart of Texas into Southeast Texas...

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

Valid 051215Z - 051730Z

SUMMARY...Rapidly weakening MCS with a few lingering over-running
thunderstorms capable of very intense rain rates and sub-hourly
rain totals of 1-3".  Incidents of flash flooding are becoming
less likely with exception of urban areas and expansion/
reinundation of already flooded areas.

DISCUSSION...Regional RADAR mosaic and GOES-E 10.3um IR loop shows
a very broad decaying MCS with rapidly accelerating outflow
boundary bisecting LA from NE to WSW extending into southeast TX.
However, a few areas of remaining cold tops exist along the upwind
edge.  This aligns with deeper moisture flux coming off the
Western Gulf coastal confluence axis that continues to stream
northward on 20-25kts of 925-850mb flow.  Surface Tds are very
rich with mid to upper 70s dotted with an spot 80F dewpoint but
the q-axis remains from South Padre Island north through Victoria
into the upwind edge with 1.7" total PWats while further east are
sub 1.5".  The instability axis is also further west of the q-axis
but still shows a greater intersection with the upwind edge; with
MLCAPE values of 3000+ J/kg.  As such, the over-running and deep
moisture convergence in proximity to mature thunderstorms and
their associated cold pools aid toward maintenance of the
convective lines.

The lead line does appear to be slowing likely due to a shallowing
of the cold pool and increasing distance from the leading outflow
edge, and is probable to merge with the stronger wave over the
next few hours in the vicinity of Limestone/Falls to Houston
counties.  Flux convergence will likely continue to support 2"+/hr
rates, though minus the timing of the merger, is likely to be
limited to a sub-hourly rain total and spots of 1.5-2.5" are more
likely the range of expected totals as the outflows/convergence
continues to surge southward into the moisture/instability axis
and eventually Gulf of Mexico. While these are quick hitters, that
will result in limited infiltration and increased run-off for
potential for flash flooding, especially in urban centers and
locations further north and east in eastern and southeastern TX
where grounds are already saturated/flooded.

Deeper layer steering of the deeper cells is becoming more west to
east in further distance from the MCV in AR, this may allow for
some increased duration too for repeating before the propagation
vectors dominate to the south, additionally supporting localized
maxima up to 2-3" in spots more likely over the next 1-3 hours.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON   32139658 32059595 31629499 31099427 30549382
            29899393 29549447 29209518 29009578 29089679
            29339731 29859779 30449799 31049800 31429783
            31769756 31959731