258
AWUS01 KWNH 201807
FFGMPD
TXZ000-210000-

Mesoscale Precipitation Discussion 1237
NWS Weather Prediction Center College Park MD
106 PM EST Thu Nov 20 2025

Areas affected...South-Central TX into the Hill Country

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

Valid 201800Z - 210000Z

Summary...Additional rainfall of 1.5-3.0" (and locally higher)
over portions of already saturated areas is likely to continue
scattered to numerous instances of flash flooding (with
expectations for locally significant flash flooding developing).

Discussion...Sustained training convection has resulted in a
narrow swath of heavy rainfall (2-5" over the past 3-6 hours, per
MRMS estimates) through the morning hours. While numerous (but
very geographically focused) flash floods are ongoing in portions
of the TX Hill Country, concerns are growing for continued
worsening of impacts as persistent low-level moisture transport
and convergence have coincided with destabilization just upstream
of the hardest hit areas (to the southwest into portions of
South-Central TX near Del Rio). The mesoscale environment is
otherwise characterized by precipitable water values of 1.4-1.7"
(near daily records, as DRT sounding climatology indicates a 90th
percentile of ~1.2"), most-unstable CAPE of 1000-2500 J/kg, and
substantial deep layer shear of 55-65 kts. While a dry line is
slowly approaching the region from the west, this is likely only
increasing the low-level forcing over the next several hours with
the expectation that the feature will stall west of Del Rio.

Going forward, there is strong agreement among the hi-res CAMs for
an additional 1.5-3.0" of rainfall (with at least one run of the
HRRR indicating localized totals of up to 5", as well as HREF 3"
exceedance probabilities of 15-25%). Given the wet antecedent
conditions (and the already relatively sensitive terrain of
portions of the Hill Country), continued scattered to numerous
instances of flash flooding are likely (including some locally
significant instances of flash flooding, as FFGs of 1.5" are lower
are indicated across already hard hit areas).

Churchill

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

ATTN...WFO...EWX...FWD...SJT...

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

LAT...LON   32459847 32329806 31959765 31639764 31299797
            30989823 30639859 30139902 29589955 29340009
            29340072 29590130 30100103 30600069 31080033
            31410010 31899969 32249924 32429888