AWUS01 KWNH 211000

FFGMPD

TXZ000-211530-



Mesoscale Precipitation Discussion 0123

NWS Weather Prediction Center College Park MD

559 AM EDT Tue Apr 21 2026



Areas affected...Triangle of Central Texas...



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



Valid 211000Z - 211530Z



SUMMARY...Flash flooding risk possible given slow

moving/back-building warm-advective shallow but efficient

showers/thunderstorms.  Rates of 1-1.25"/hr are possible with

localized 2-3" totals.



DISCUSSION...A very effective dynamic environment is helping to

draw above normal moisture into a favorable ascent pattern over

the next few hours across the Triangle of central Texas.  GOES-E

WV suite depicts a decaying MCV across southeast TX along the

southeast periphery of favorable mid to upper-level divergent

pattern along the northeast quadrant of a 70kt 3H west to east jet

along/north of 30N.  Combined with NW to SE diffluent pattern from

500-250mb providing strong divergence for effective convective

outflow.  However, it is also directing strong ageostrophic

forcing by helping to accelerate the early morning western Gulf

jet streak fluxing enhanced low level moisture northward into the

isentropic ascent plane.  CIRA LPW along with VWP vectors denote

core of west Gulf jet is propagating 20-25kts in the core of .8 to

1" moisture in the surface to 850mb layer.  Combine this with the

axis of 700-500 mid-level moist flow from the subtropical eastern

Pacific results in combined PW values nearing 1.5" near the best

isentropic ascent currently through the San Saba River Valley.



As such, recent 10.3um EIR and RADAR show increasing shallow

convective activity along the NW to SE oriented DPVA into the best

diffluence/divergence region downstream.  The only limiting factor

is the lack of higher theta-E air resulting in a broader unstable

layer.  Currently, it is limited to 100-250 J/kg of MUCAPE but

only expected to increase toward 500 J/kg toward mid-morning as

the core of the western Gulf air reaches the area of concern. 

Deep layer flux and ascent should allow for solid convergence and

low level precipitation development likely with smaller droplets

in warm-cloud process generation.  This should allow for increased

rainfall rates, but without the greater vertical depth, is likely

to be limited to the 1.25" range at max.  Convective cells are

likely to move toward the northeast, but with continued south to

southwest low level inflow, propagation vectors should be

supportive of upstream redevelopment/back-building of the shallow

cores.  This should allow for increased overall duration to

potentially support highly focused/localized maximum totals of

2-3" through to afternoon. 



Hydrologically, these maximum totals are at the minimum thresholds

of 1 but more likely 3 hour FFG values in the area, particularly

along the southwest edge of the area of concern. NASA SPoRT LIS

0-40cm soil conditions suggest average saturation around 45-55%

and as such, most rainfall will be beneficial, but an isolated

incident or two of flash flooding is considered possible given the

strong dynamics and setup's history. 



Gallina



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



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



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



LAT...LON   32539720 32209657 31769628 31419629 31169645 

            30919666 30589712 30449755 30679836 31159887 

            31779894 32509834