Mesoscale Precipitation Discussion 0759
NWS Weather Prediction Center College Park MD
308 AM EDT Tue Sep 04 2018

Areas affected...Southeast TX

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

Valid 040705Z - 041215Z

Summary...A cluster of heavy showers and thunderstorms will be
arriving in off the Gulf of Mexico over the next couple of hours
with very heavy rainfall rates. Given the very heavy rainfall over
the last 24 hours, flash flooding will be likely.

Discussion...Cooling convective tops are seen evolving offshore of
the upper TX coast as showers and thunderstorms approach within a
low to mid level southeast flow regime. The activity is seen
developing in within an axis of slightly stronger low level speed
convergence that is shifting off to the west-northwest across the
northwest Gulf of Mexico, but also within a moderately unstable
and very moist environment. In fact, MLCAPE values are on the
order of 1500 to 2000 j/kg and PWATS running in excess of 2.25
inches along and just offshore of the coast.

This convective band is expected to move across the upper TX coast
over the next 1 to 2 hours and become a bit better organized as it
interacts with a surface trough along the coast. The additional
rainfall will occur areas that have seen in excess of 4 to 8
inches of rain over the last 24 hours which will greatly enhance
the concerns for additional runoff problems and flash flooding.
This will include areas from Beaumont/Port-Arthur down to
especially the Galveston area.

The additional rainfall based on the latest satellite trends and
HRRR output is expected to be as much as 3 to 4 inches locally,
and much of this will be a result of enhanced rainfall rates and
concerns for at least some brief training of cells. Flash flooding
will be considered likely given the saturated soil conditions.
Will continue to monitor.

Orrison

ATTN...WFO...HGX...LCH...

ATTN...RFC...LMRFC...WGRFC...

LAT...LON   30109419 30069373 29789358 29629407 29609416
            29509438 29159498 29189521 29339529 29589527
            29909493