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
...Please see
www.wpc.ncep.noaa.gov for graphic product...
ATTN...WFO...EWX...HGX...
ATTN...RFC...FWR...NWC...
