Mesoscale Precipitation Discussion 1000
NWS Weather Prediction Center College Park MD
615 PM EDT Wed Oct 31 2018

Areas affected...East TX into far southwest LA

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

Valid 312215Z - 010215Z

Summary...Training and merging cells could produce hourly rainfall
rates near 2.00 inches over portions of east TX into far southwest
LA. This poses a flash flood threat into the evening hours.

Discussion...Regional radars across east TX indicated an increase
in coverage of convection late this afternoon. The convection was
developing in an area of 1500-2500 J/KG of MLCAPE, well in advance
of a cold front stretching from northeast into central TX. The
GOES-16 clean IR loop showed bursts of cloud tops temperatures
near -70 C, as the individual cells tracked eastward. 

A 25 to 35 knot low level southerly flow (per regional VWP)
continued to supply 1.75/2.00 inch precipitable water air to the
region. Due to the deep moisture feed, hourly rainfall rates from
the KHGX radar have been consistent between 1.50 and 2.00 inches,
especially near the Houston metro area. Thus far, the convection
has been scattered, which has lessened the overall flash flood
threat.

However, as the convection ahead of the cold front over central TX
moves east, cell mergers and short term training become
increasingly possible. Additionally, divergence in the right
entrance region of an 80 knot jet streak ove northern AR could
allow the convection to become better organized. In this airmass,
hourly rainfall rates could top 2.00 inches. One and three hour
flash flood guidance values are generally above 2.50 inches, so
training would need to occur for flash flooding to initiate.

The most recent HRRR indicated the potential for training over
portions of east TX and nearby far southwest LA through 01/02z,
showing local 2.00 to 4.00 inch rainfall amounts, including near
the Houston Metro area. Due to relatively high flash flood
guidance values, flash flooding is considered possible.

Hayes

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

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

LAT...LON   31659405 31529336 31069286 30269289 29729363
            29109497 28919618 29579641 31339487