Mesoscale Precipitation Discussion 1001
NWS Weather Prediction Center College Park MD
834 PM EDT Wed Oct 31 2018

Areas affected...Portions of southern and eastern TX...northern
LA...southern AR

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

Valid 010035Z - 010435Z

Summary... Convection training ahead of a frontal boundary
extending from AR across south TX could produce hourly rainfall
rates near 2.00 inches. This will pose a flash flood threat into
the late evening hours.

Discussion...Regional radars indicated convection along and ahead
of a frontal boundary extending from northern AR into South TX.
The GOES-16 clean IR loop showed cloud top temperatures between
-65 and -70 C, as the entire area of convection moved eastward.

Convective clusters in the area were moving northeast along and
ahead of the front, resulting in training near portions of the mid
and upper TX coast, generally north and west of the Houston metro
area. The KHGX radar showed hourly rainfall rates between 1.50 and
2.00 inches along and just ahead of the front with the highest
rates over Liberty and Hardin counties.

Despite the slow march eastward of the front, training along and
ahead of the front over portions of southern and eastern east TX
could produce local 2.00 to 4.00 inches of rainfall, and these
amounts are supported by the most recent HRRR runs. Three hour
flash flood guidance values here are generally above three inches
(except areas near Houston, which saw heavy rainfall earlier this
evening). Therefore, training would be necessary to initiate flash
flooding.

Further northeast into northern LA and southern AR, the
instability is not as robust, and cloud top temperatures have been
slowly warming. However, a 40 knot low level southerly flow (per
regional VWP) transports 1.50/1.75 inch precipitable water air
over these areas. As a long wave trough approaches from eastern
NM/west TX, the mid level flow is expected to back, and this could
enhance the threat for training.

Due to the lower instability across northern LA and southern AR,
the most recent HRRR rainfall amounts were not as high as further
south. Because of this, flash flooding is only considered
possible.

Hayes

ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LZK...MEG...SHV...

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

LAT...LON   34549203 34169097 32059249 30989375 29589571
            29119714 29249789 30079767 31769613 32469533
            32579521 34179338