101
AWUS01 KWNH 151240
FFGMPD
TXZ000-151700-

Mesoscale Precipitation Discussion 0416
NWS Weather Prediction Center College Park MD
839 AM EDT Mon Jun 15 2026

Areas affected...Deep South Texas...

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

Valid 151240Z - 151700Z

SUMMARY...Extreme rates to 2.5-3"/hr with training elements may
result in a narrow band of 3-5" totals and possible incidents of
flash flooding.

DISCUSSION...Broad scale cyclonic circulation over north-central
Mexico continues to drive highly anomalous moisture flux off the
western Gulf with deep layer fetch resulting in 2.5"+ Total PWATs
though the bulk is below 850mb with CIRA LPW suggesting 1.25"+
values in an axis along the eastern flank of the deeper
circulation across Deep South Texas.   Surface to boundary layer
inflow is deflected slight toward the east relative to the deep
layer south-southeasterly unidirectional flow above the boundary
layer to further enhance convergence to spark convergence.
Combine this with proximity to the western gradient of highly
unstable 2500 J/kg SBCAPEs, noting that the profile is very narrow
at least to 500mb.  Warm cloud layer to 16Kft+ also suggests
collision/coalescence efficient rainfall production with fairly
consistent potential for 2.5-3"/hr rates.  Given the potential for
multiple cores of convection within the deep unidirectional flow,
there may be increased residency due to training/repeating
allowing for localized 3-5" totals over the next few hours.  This
surge in convergence, instability will slacken a bit as the
low-level shortwave feature continues to slide northward through
the Lower Rio Grande Valley toward Maverick county and E Coahuila
state in the next few hours.   As such, Hi-Res CAMs and
observational trends suggests only a few hours of ideal training,
but this is uncertain given how storms may have potential
feed-back to aid weak cold pool to maintain convergence.

Hydrologically, the area should train through very sandy/accepting
soil conditions where FFG values are 3-4"/hr and 4-5"/3hrs with
exception to the near Rio Grande Valley and urban centers there
in.  So potential is greater there, but with those rates/training
and potential for some longer duration of training compared to
current Hi-Res CAM trends; incidents of flash flooding are
considered possible through the next few hours.

Also, will be watching the trends of instability advection further
westward closer to the main core of the low-level vorticity center
in Zapata into Webb county for potential of an additional
necessity for an MPD... but for now, that is too conditional to be
included with this area of concern.

Gallina

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

ATTN...WFO...BRO...CRP...

ATTN...RFC...FWR...NWC...

LAT...LON   27639846 27269818 26259766 25949772 25989800
            26109836 26689861 27409891