Mesoscale Precipitation Discussion 1255
NWS Weather Prediction Center College Park MD
1056 PM EST Sat Nov 29 2025

Areas affected...Central and Upper Texas Coastal Plain...

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

Valid 300400Z - 301000Z

SUMMARY...Slow moving, pre-frontal cells with rates of 2"/hr
eventually merge with south-southeastward pressing cold front
convection resulting in localized 2-4" totals in 1-3 hours. 
Isolated flash flooding remains possible, especially near urban
centers.

DISCUSSION...GOES-E 3.9um SWIR highlights a few low level
boundaries that will remain the focus of scattered thunderstorm
activity through the overnight period.  The main being the surging
cold front being reinforced by favorable upper-level orientations
to support steepening of theta-E gradient while increasing
northerly surface wind flow to over 20-25kts nearly counter to the
weaker but solid onshore flow.  Currently active convection along
the leading edge of the front is slow moving from Burleson to Polk
county as the winds are not fully intersecting with the line, but
will likely be propagating southward in the next hour or so.  The
other boundary is the return moisture plume off the western Gulf
(which arches similar to the Lower TX Gulf coast before angling
east- northeast just south of the aforementioned convection).  Tds
in the upper 60s to near 70 can be traced best in CIRA LPW sfc-850
and 850-700mb layers covering much of the MPD area of concern
across the Central and Upper Texas Coastal Plain.

Onshore flow is also increasing to 15-20kts resulting in
frictional convergence near coast.  Conditionally unstable airmass
with MLCAPEs of 1000-1250 J/kg remain weakly capped but there are
some signs in satellite imagery of some weak cu field near
Victoria, TX  as well as an isolated weakening supercells
northeast of Galveston Bay.  The merging of the boundaries is also
allowing a westward expansion of new development upstream into
Bastrop/Caldwell county vicinity. 

Total deep moisture of 1.5" as noted in the CIRA LPW is loaded
below 700mb, but there is solid deep saturation.  These isolated
cells driven by frictional convergence will be slow moving and
eventually capable of 1-2"/hr rates.  Spotty 2-3" totals will
occur in 1-2hrs, but as they mature and expand the slower moving
cells along the cold front will have started increased forward
speed and with very high low level moisture flux convergence will
have the capability of 1-1.25"/15min rainfall totals as they
intersect/merge with the cells across the Plain.

00z HREF probabilities continue to suggest 3"/3hr totals in the
20-30% range (3"/6hr over 50%) which is fairly impressive given
the strength of the updraft due to instability is fairly limited. 
While the overall coverage will continue to be limited, spots of
3-4" totals are probable through 09z.   This places sufficient
overlap of FFG exceedance (as 1hr FFG is 2.5-3" and 3hr is 3-4")
for possible localized incident or two of flash/rapid inundation
flooding.  This only further increases with intersection with
urban centers, such as Victoria, Houston and Beaumont.  

Gallina

ATTN...WFO...CRP...EWX...HGX...LCH...

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

LAT...LON   30999472 30719393 30099362 29749380 29519420
            29359466 28499607 27779725 27969777 28499795
            29529752 29879714 30199681 30729602