Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
858 PM EDT Tue Apr 28 2026
Day 2
Valid 12Z Wed Apr 29 2026 - 12Z Thu Apr 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM CENTRAL AND
SOUTHEAST TEXAS TO THE CENTRAL GULF COAST...

...2030Z Update...

The inherited Marginal Risk was largely maintained with this
update. While high resolution guidance now fully encompasses the
entirety of the Day 2 period, a lack of agreement on the placement
and behavior of the convection does not lend itself to a Slight
Risk upgrade at this time. Were one to need to be issued, it
appears that portions of northern Louisiana and into southern
Mississippi would be the area to highlight. This would be largely
dependent on how much convection the area gets tonight with the
current convection, as saturated soils across Louisiana would make
flash flooding more likely again on Wednesday. As mentioned in the
previous discussion below, PWATs will be well above normal for
this time of year, supporting storms capable of very heavy rains.
Advection into the region will be weak...noting that the stalled
front along which any storms from Texas through Alabama would
likely form, will also be lacking in forcing. The upper levels will
be of minimal help for the storms as well, as a weak fast moving
shortwave traverses the region along the jet, likely initiating
some convection across the Lower Mississippi Valley, but then
quickly departing that convection.

Wegman

...Previous Discussion...

The outlook for Day 2 has remained mostly unchanged, with a
Marginal Risk in a corridor from Texas through Alabama along the
western and central Gulf Coast. A threat of excessive rainfall and
flash flooding is expected, due to a continuation of strong
instability, and the arrival of a plume of unusual amounts of mid-
level moisture. Backward trajectory analysis indicates moisture
around 3km above the surface can be traced along an anomalously
strong subtropical jet extending back into the tropical central
Pacific Ocean. This should push PW values over the risk area above
1.7 inches, and above 2 inches in portions of Texas, which is quite
unusual for April. Given this, it's possible an upgrade to Slight
Risk may be needed in future outlook updates. However, hi-res
guidance is just coming into view. While the extended HRRR and RRFS
do both show rain rates in this environment reaching (and even
exceeding, in some cases) 2 inches per hour, confidence is not high
on placement of greater concentrations of convection. Additionally,
there doesn't seem to be much signal for backbuilding and training,
except perhaps via cell mergers, which could lead to more limited
duration of heavy rain. Therefore, the risk level was held at
Marginal for now for the entire region.

Lamers

Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt