Mesoscale Precipitation Discussion 1254
NWS Weather Prediction Center College Park MD
452 PM EST Sat Nov 29 2025

Areas affected...Southeast Texas

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

Valid 292151Z - 300351Z

Summary...Thunderstorms near Houston TX are expected to grow
upscale and potentially backbuild/train with time.  Hourly amounts
to 2.5" with local totals to 5" could lead to widely scattered
instances of flash flooding.

Discussion...Satellite and radar imagery indicate the formation of
showers and thunderstorms near and east of a baroclinic zone
oriented northwest-southeast across Southeast TX within a region
of 850 hPa confluence near I-10.  ML/MU CAPE to the west and
southwest is 1000-2000 J/kg.  Effective bulk shear is near 40 kts,
which has led to right movers near IAH itself.  The atmosphere is
saturated, considering precipitable water values (1.25-1.5" per
GPS data) within a region of 5630 meter 1000-500 hPa thickness
values.  Hourly rain amounts of are up to 0.5-1" in the past hour
near Stagecoach TX, as of the time of this discussion's writing.

The 18z HREF moreso than the 12z REFS indicates the continued
building of thunderstorms in this area, with some further increase
in convective coverage, which may show backbuilding, training
character with time.  Instability could erode/retreat westward
with time depending upon the degree of convective coverage,
essentially stalling the front west of Houston.  Cell mergers are
also possible as less organized convection moves more northeast
while more organized convection moves more to the east.  Given the
parameters, hourly amounts to 2.5" with local amounts to 5" are
possible over the next several hours, with the magnitude most in
line with the 12z ARW and 20z HRRR guidance.  There is a chance
late in the MPD period of convection trying to form across
northeast TX presently near and ahead of an advancing cold front
approaching the southeast TX convective area, which could lead to
more cell mergers at or beyond 04z.  Since the 12z ARW and 18z
HREF are closer to the convective evolution thus far, used their
guidance for the defined MPD area.  Widely scattered instances of
flash flooding are considered possible, particularly in the
Houston metropolitan area.

Roth

ATTN...WFO...EWX...HGX...

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

LAT...LON   30579626 30439491 29959459 29489490 29339650
            29869717