500
AWUS01 KWNH 111954
FFGMPD
TXZ000-120152-

Mesoscale Precipitation Discussion 0423
NWS Weather Prediction Center College Park MD
353 PM EDT Tue Jun 11 2024

Areas affected...Portions of Central TX including the Hill Country

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

Valid 111952Z - 120152Z

SUMMARY...Some uptick in the coverage of showers and thunderstorms
can be expected over the next few hours heading into the evening
time frame. A localized and mainly urban flash flood threat will
exist from heavy rainfall rates.

DISCUSSION...The mid-afternoon GOES-E visible satellite imagery
shows a well-defined MCV over north-central TX which continues to
facilitate the southeast advance of a long-lived outflow boundary
down toward the TX Hill Country. The southern flank of the outflow
boundary is expected to become increasingly aligned west to east
in nature over the next few hours while still gradually losing
latitude with time. There is a rather substantial amount of
moisture and instability in place over south-central TX that will
be pooled up along this boundary going into the evening hours.

MLCAPE values have risen locally to as high as 1500 J/kg, and some
additional short-term uptick in instability is expected with the
full diurnal heating cycle. The low levels of the column are very
moist with dewpoints in the low to mid 70s, and PWs overall are
close to 1.75 inches based off the latest NESDIS Blended-TPW and
GPS-derived data.

Forcing along the outflow boundary will be somewhat modest, but
there is about 30 to 40 kts worth of effective bulk shear with at
least a somewhat diffluent flow pattern aloft around the southeast
flank of the aforementioned MCV. The 12Z HREF guidance suggests
some increase in convective coverage over the next few hours, and
sufficiently high enough rainfall rates for some localized 1-hour
and 3-hour FFG exceedances.

Rainfall rates are expected to increase to as much as 2.0 to 2.5
inches/hour, and with rather slow cell-motions and some potential
for repeating cell-activity, some spotty storm totals may reach 3
to 4 inches. In time, the overall convective threat should tend to
bow farther down to the south and east, and this will favor more
areas of the TX Hill Country including areas around the San
Antonio and Austin area to see a threat for heavy rainfall.

Any flash flooding threat should tend to be localized, but this
will include an urban flash flood threat should these locally very
heavy rainfall rates make it into the more urbanized locations.

Orrison

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

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

ATTN...RFC...WGRFC...NWC...

LAT...LON   31769651 31469604 30249603 29339662 28919759
            28789862 29099970 29850020 30490000 30779938
            30979794 31669705