AWUS01 KWNH 081237
FFGMPD
TXZ000-081700-

Mesoscale Precipitation Discussion 0050
NWS Weather Prediction Center College Park MD
736 AM EST Sun Mar 08 2026

Areas affected...South-central Texas...

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

Valid 081235Z - 081700Z

SUMMARY...Slow moving cells capable of 1.75"/hr rates near the
Southern Balcones Escarpment/San Antonio Metro may pose localized
flash flooding concerns through mid-morning.

DISCUSSION...EWX RADAR and GOES-E 10.3um EIR continue to show
increasing coverage and cooling top/intensifying thunderstorms
across south-central Texas.  Return weak southerly moisture flux
over the shallow cold front across Deep South Texas combined with
favorable divergence in the exit/diffluence of upper-level jet max
has enhanced scattered early morning shower activity into
deeper/broader updrafts capable of intense rainfall.   VWP at EWX
combined with RAP analysis suggests a recent uptick in 850-700mb
flow to 15kts, but generally into the northern limit to the weak
isentropic ascent providing this additional convergence to
generate/expand convective activity.  CIRA LPW shows sfc-850 and
850-700mb tight moisture gradient indicative of the shallow front
with values near .8-.9 and .5" respectively.  The loading of this
1.5 to 1.75" total PWat into the cells has increased rainfall
efficiency to support 1.5-1.75"/hr rates, especially the broader
cell in Bexar county, which also shows solid suggestion of upwind
redevelopment. 

Deep layer steering driven mainly below 700mb has more of a slow
northward shift within broadly westerly flow, which is also nearly
parallel to the moisture/flux gradient.  This may allow for short
periods of repeating to allow for hour plus duration or random
training/repeating from upstream cells too.  Spots of 2-3" are
possible in 1-2 hours though the mid-morning (through 15-17z)
until favorable jet divergence slides further eastward/weakens as
well. 

Proximity to San Antonio Metro/broad urban center and Balcones
Escarpment will likely be the greatest driver of flash flooding
potential.  Naturally low FFG along/north of the city with hourly
values between 1.5-2" are well within the potential of low-end
exceedance and suggestive of localized possible incident or two of
flash flooding, especially if combined with hydrophobic urban
setting, further compounding run-off potential.  Though south of
the escarpment across the sandier Coastal Plain, FFG values
increase rapidly and therefore flooding risk would be considerably
lower, but still non-zero. 

Gallina

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

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

LAT...LON   29999741 29759663 29389614 28909595 28569640 
            28349786 28389910 28619953 28919971 29259965 
            29649922 29919843 

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