587
AWUS01 KWNH 121747
FFGMPD
MSZ000-LAZ000-TXZ000-122345-

Mesoscale Precipitation Discussion 0258
NWS Weather Prediction Center College Park MD
146 PM EDT Sun May 12 2024

Areas affected...East Texas into Central Louisiana

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

Valid 121745Z - 122345Z

SUMMARY...Flash flooding threat continues over east Texas while
expanding into central Louisiana into this evening as scattered
heavy thunderstorms shift east along a low level boundary.

DISCUSSION...Radar imagery at 1730Z depicts an expanding cluster
of elevated heavy thunderstorms over east Texas north from the
northern Houston metro where a warm front is approaching. This
activity continues moving east as persistent 35kt SWly deep layer
mean flow is counteracted by Wly upwind propagation vectors.
Rainfall of 1" has been estimated over the past hour with the
easternmost cell that is approaching the LA border. Cells farther
west are producing around 1"/hr rates, but overlap with a swath of
2-3" extending east from Waco.

Elevated instability remains somewhat limited (but sufficient) at
1000-1500 J/kg of MUCAPE. Upper level SWly flow is from a
positively-tilted trough still over CO/NM that is advecting
Pacific moisture in across Mexico while low level flow over the
warm front is bringing moist flow from the western Gulf of Mexico
with PWs in east Texas of 1.8-2.1" which is 3 sigma above normal.

HRRR runs starting at 15Z have been more disperse with rainfall
over this area than the 13/14Z runs, but the rapid development of
heavy thunderstorms in waves coming off the warm front and over
rather sensitive areas north of Houston from extreme rainfall over
the past couple weeks.

3hr FFG is generally 2.5 to 3.5" in the sensitive area north of
Houston and closer to 4" into central LA. The main limitation
remains shear with Wly 0-6km bulk shear values now 60kt which
should maintain a somewhat scattered convective mode. However,
given the sensitivity of the area north of Houston, localized
flash flooding should be expected there. Rainfall of 3-4" is
possible in central LA where flash flooding is also possible.

This warm front stalls this evening, so further heavy rain and
flash flooding threats are forecast across this area overnight.


Jackson

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

ATTN...WFO...FWD...HGX...JAN...LCH...LIX...SHV...

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

LAT...LON   31869571 31829405 31589237 31269152 30499167
            30259267 29889415 30069579 31589672