658
AWUS01 KWNH 161702
FFGMPD
TXZ000-162100-

Mesoscale Precipitation Discussion 0275
NWS Weather Prediction Center College Park MD
101 PM EDT Thu May 16 2024

Areas affected...West-Central Texas to the Upper Texas Coast

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

Valid 161700Z - 162100Z

Summary...Thunderstorms across Texas will expand through the
afternoon and intensify along a surging warm front. Rainfall rates
are expected to reach at least 2-3"/hr, which could produce 2-3"
of rain with isolated higher amounts. Flash flooding is likely.

Discussion...Convection continues to blossom late this morning as
the setup becomes increasingly more impressive across Texas. The
recent WPC surface analysis indicates a wave of low pressure
moving out of NM, with a stationary front draped to its northeast.
Just east of these features, a potent warm front is beginning to
lift northward, along which dew point temperatures are steadily
climbing into the upper 70s and even low 80s. This is evidence of
the strong theta-e ridge bulging from the south, which will
continue to follow the warm front northward providing an
exceptionally favorable thermodynamic environment for
strenghtening through diffluence within the LFQ of a subtropical
jet streak, mid-level divergence downstream of a trough axis in
NM, and through isentropic ascent as the low-level flow
responsible for the theta-e advection lifts atop the warm front.
This combination is resulting in the expansion and intensification
of high reflectivity across TX already.

As the warm front continues to lift northward, the environment
will additionally destabilize, with SBCAPE progged to reach
3000-4000 J/kg. Overlapping this instability, PWs emerging from
the Gulf of Mexico may climb towards 2.2 inches, which would be
above the daily record for portions of south/central TX.
Intensifying ascent into this environment will almost certainly
support expanding and intensifying thunderstorms, and the HREF
neighborhood probabilities for 2"/hr reach above 30%, with HRRR
15-min rainfall suggesting brief periods of 4"/hr rain rates
likely.

These rates themselves could be enough to overwhelm soils to drive
rapid runoff and instances of flash flooding. However, convection
is likely to redevelop primarily along or just north of this warm
front, with Corfidi vectors aligned parallel to the front
suggesting repeated rounds of thunderstorms moving west to east
across the same areas. This will likely produce 2-3" of rain with
locally higher amounts, which will be falling atop soil moisture
that is above the 95th percentile according to NASA SPoRT from
14-day rainfall 300-600% of normal.

There remains some uncertainty into exactly how this will evolve
in the next few hours both due to timing of the warm front and how
any outflow boundaries will impact the evolution. Flash flooding
is likely through the next few hours, but the worst impacts may
still delay until this evening when additional MPD issuances will
almost certainly be needed to address what could become a
significant flash flooding event.


Weiss

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

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

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

LAT...LON   32629960 32579876 32319626 31929448 31719418
            30989387 30309405 30069433 29749513 29739630
            29889747 30049849 30179933 30280008 30610095
            31330139 31990114 32460046 32589990