327
AWUS01 KWNH 131418
FFGMPD
TXZ000-131916-

Mesoscale Precipitation Discussion 0668
NWS Weather Prediction Center College Park MD
1017 AM EDT Sun Jul 13 2025

Areas affected...Texas Hill Country

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

Valid 131416Z - 131916Z

SUMMARY...The flash flood risk continue this morning across
portions of the Texas Hill Country. The extent and magnitude of
the event has lowered from what occurred last night into the early
morning hours, however some additional flash flood impacts are
likely...and localized significant impacts remain possible.

DISCUSSION...Latest radar imagery this morning continues to show
an axis of heavy rainfall across portions of the TX Hill Country
resulting in areas of flash flooding. The eastern edge of this
activity has weakened over the past couple hours, likely due to
the low level flow becoming more parallel to the outflow resulting
in decreased convergence. However the western area of convection
has been able to persist, with low level inflow more perpendicular
to this portion of the outflow. This activity has continued to
show signs of some forward propagation off the south, which is
having the overall effect of slightly lowering hourly and total
rainfall magnitudes.

Going forward the expectation is that this gradual southward
propagation should continue as low level inflow continues to
undergo the typical diurnal weakening. This should result in a
gradual downward trend in the overall magnitude of the event going
through the rest of the morning. Probabilities of exceeding 2" in
an hour rainfall in both the 06z HREF and REFS decrease this
morning, and that aligns with the above thinking as well. However
1" per hour rainfall probabilities remain in the 40-70% range into
the early afternoon hours. Given the impressive pool of
instability to the south (within the inflow region of the
conevction), the divergent flow at 300mb, and continued influence
from the MCV...it makes sense that convection will persist to some
extent into the afternoon hours as the MCS gradually shifts
south...and recent IR cloud top cooling supports convective
persistence.

As mentioned above, the organization and overall rainfall
magnitude should continue to generally decline...however that does
not mean that locally heavier rainfall amounts will not occur.
With PWs around 2", convection will still be capable of dropping
1-2" in an hour...enough to cause some additional flash flood
issue in any more vulnerable locations. In addition, some discrete
cell development south of the convective line is probable...and
any discrete cells that do form will likely merge with the
convective line/cluster causing it to temporarily slow and
increase rainfall duration. Where this occurs we could still see a
more localized event of 2-3" per hour rainfall. So while, on
average, most places will pick up an additional 1-3" of rain,
localized totals of 3-5" remain possible. On a broad scale the
flash flood risk should be less severe than what we saw overnight
in areas just to the north...however localized more significant
impacts remain possible.

Chenard

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

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

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

LAT...LON   31150012 30859938 30799885 30859825 30659795
            30329774 29999758 29649796 29359830 29259870
            29149987 29300036 29600047 29860054 30220092
            30670133 31000131 31090087 31130061