Mesoscale Precipitation Discussion 0592
NWS Weather Prediction Center College Park MD
138 AM EDT Sat Jul 05 2025

Areas affected...central TX

Concerning...Heavy rainfall...Flash flooding likely

Valid 050537Z - 050935Z

SUMMARY...Localized heavy rainfall will be likely across portions
of central TX over the next 2-4 hours. Flash flooding will result
from rainfall rates in excess of 3 in/hr at times, especially if
heavy rain cores can edge eastward toward Austin/Round Rock and
the I-35 corridor.

DISCUSSION...0510Z radar imagery from KGRK showed a slow moving
thunderstorm in western Travis County with MRMS-derived hourly
rainfall of 4 to 5 inches and at least one gauge report from LCRA
of 4.98 inches per 60 minutes ending 0510Z near Largo Vista. This
cell appeared to be located just north of a remaining mesoscale
circulation just on the cool side of a remnant rain-cooled
boundary from Friday's rainfall combined with a trough/wind shift
axis that extended southwest to the Rio Grande across Webb County.
SPC mesoanalysis and 04Z RAP data valid at 05Z showed a stable
airmass across the Hill Country and northern TX while MLCAPE of
500-1000 J/kg resided along and southeast of I-35 from Austin
southward. 00Z soundings from DRT, FWD and CRP showed PW values at
or above the 90th percentile and tropical moisture was still in
place in the vicinity of an elongated low-mid level low which was
located over central TX.

S to SSE 850 mb winds of 10-20 kt are expected to continue
overnight with advection of weak instability back toward the
northwest and focused convergence near the remnant mesoscale
vortex. Weak deeper mean layer winds of 10 kt or less will favor
slow to nearly stationary movement of heavy rainfall with hourly
rainfall exceeding 3 inches at times. The duration of the core of
heaviest rainfall is uncertain, and it may begin to drift to the
northwest as the instability gradient pushes northwest over the
next couple of hours. However, present trends indicate near
stationary net movement with continued very high rainfall rates
continuing in the vicinity of western Travis/Williamson and
eastern Burnet counties.

Otto

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

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

LAT...LON   31769776 31619741 31219713 30789731 30409750
            30069771 30039796 30249830 30689845 31489825