Mesoscale Precipitation Discussion 1013
NWS Weather Prediction Center College Park MD
1144 PM EST Wed Nov 07 2018

Areas affected...Far Southeast TX...Southern LA

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

Valid 080440Z - 080930Z

Summary...Slow-moving and locally training showers and
thunderstorms will continue over the next several hours. Flash
flooding is likely.

Discussion...The latest IR satellite imagery showing an expansion
of cold convective tops across portions of southeast TX and
southwest LA where there is a wave of low pressure advancing
gradually east along a well-defined frontal zone.

A strong instability gradient is noted across the region and much
of the activity is along the north side of the gradient and in
conjunction with the best low level surface convergence.
Additionally, there is a shortwave advancing east across the
lower/middle MS Valley region which is providing sufficient DPVA
for additional deep layer ascent in vicinity of the front.

PWATS in vicinity of the front across southeast TX and southern LA
are around 2 inches, and this will allow for locally efficient
convection with enhanced rainfall rates. The latest HREF
probabilities support rainfall amounts of as much as 2 to 2.5
inches/hr, and with the slow cell motion off to the east and some
small-scale training along the front, there will likely be some
enhanced storm totals.

In fact, the latest HRRR guidance supports as much as 3 to 6
inches of rain locally, with the heaviest amounts focusing over
southwest LA. The convection should tend to weaken toward 09Z, but
in the meantime, these rainfall amounts are likely to result in
some flash flooding.

Orrison

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

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

LAT...LON   30399378 30359318 30279238 30139112 29818975
            29578932 29308918 29068936 29029008 29129096
            29279165 29499232 29669318 29669386 29629435
            29679489 29959504 30179485 30309453