Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Tue Jun 16 2026
Day 1
Valid 12Z Tue Jun 16 2026 - 12Z Wed Jun 17 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE TEXAS GULF COAST THROUGH THE LOWER MISSISSIPPI VALLEY...

An impressive and dynamic setup with multiple mesoscale features
is expected to develop through the day today from the Texas Gulf
Coast through the lower Mississippi Valley. The most rainfall for
the day will occur through this morning. A tropical disturbance
over Deep South Texas will support the strengthening of the typical
diurnal low level jet out over the Gulf, driving a plume of
impressively deep tropical moisture northward into the Texas and
Louisiana Gulf Coasts. Meanwhile a stationary front currently over
southern Arkansas and northern Mississippi will advance southward
as a cold front due to a disturbance and push of cooler drier air
south behind the front. This clash of air masses will result in
continued upscale development of storms that have broken out over
northern Louisiana through the overnight and into Tuesday morning.
FFGs are already lower in many spots west from the western tip of
Mississippi. This nearly stationary line of training storms is
likely to persist well into the afternoon, which could make for a
narrow but nevertheless severe area of very high totals of storm
total rainfall, especially into western Mississippi. Guidance has
suggested this narrow corridor, highlighted in much of the guidance
since yesterday along the I-20 corridor has now shifted a few
counties south, extending from Alexandria, LA east almost to
Hattiesburg, MS. The inherited Moderate Risk for this area was
trimmed on the north side both with the current start of convection
in this corridor and the southward trend in the guidance.

Meanwhile, a number of other pieces of CAMs guidance suggest that
the showers and storms developing along the immediate coast roughly
from Galveston/Trinity Bays east to Lafayette, LA will be the
primary and dominant line of showers and storms impacting the
northwestern Gulf Coast today. This line would from largely from
sea breeze/frictional convergence of the strong onshore southerly
flow into the coast. The front to the north may play a role in
maintaining the storms where they are, but would likely play a
secondary role. Should this line develop robustly, it will force
the aforementioned line of storms over northern LA/southwest MS
eastward, resulting in less rain over northern/central LA. Most
likely there will be a combination of the two, with the east-
northeastward moving storms along the southwest Louisiana coast
continuing with the line to the northeast over western Mississippi.
Once again the Moderate Risk here remains in place with few
changes.

Finally, further south along the Texas Gulf Coast, the larger
synoptic level disturbance, responsible for the heavy rains and
flash flooding over Deep South Texas yesterday will likely eject
east into the Gulf today. As it does so, it will create localized
bands of heavy rain along the Middle Texas Coast, which will then
advect northeast to join the line east of Houston. This area from
Corpus Christi to Houston remains the most uncertain portion of the
Moderate Risk area, as a small south/east shift in the track of the
disturbance will take the lion's share of the associated rainfall
ahead of the low track out over the open Gulf, and greatly limit
any rainfall today along the coast. The inherited Moderate Risk was
trimmed completely south of Corpus Christi, with just a Slight
along the immediate lower Texas Gulf Coast to account for ongoing
rains in the area. The threat will shift off the coast by late this
afternoon.

With all three areas of heavy rain above, they will all diminish
and dissipate as a significant heavy rain threat by this evening.
Occasional showers and a storm or two may impact the immediate Gulf
Coast through the overnight, but for the most part the heavy rain
threat through tonight should be minimal.

Wegman


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt