Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
858 PM EDT Tue Jun 16 2026
Day 3
Valid 12Z Thu Jun 18 2026 - 12Z Fri Jun 19 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST...
...2030z Update...
...Lower Mississippi through central Georgia...
The inherited moderate risk area was expanded south and east to
include places like the Atlanta metro area, due to concerns of
urban flash flooding. Models are still uncertain as to where
exactly the heaviest rainfall will occur, however, antecedent
rainfall should still support flash flooding in many parts of the
Lower Mississippi Valley if convection/rain occurs.
Kebede
...Previous Discussion...
...Lower Mississippi Valley through Central Alabama...
The tropical low and its associated moisture are expected to start
the Day 3 period over northern Louisiana or western Mississippi.
The leading band of heavy rain will be ongoing from eastern
Louisiana into southern Mississippi. The low will slowly drift
eastward across Mississippi through the day, then gradually
increase its forward speed Thursday night as it tracks east across
Alabama and ends the period in northern Georgia. A very persistent
heavy band of rain will remain south and east of the low center
throughout the Day 3 period. This will focus the heaviest rains in
the Moderate Risk corridor from central Louisiana through central
Alabama. Prolonged southerly flow of the deep tropical moisture
with PWATs to 2.5 inches will support development and redevelopment
of convection ahead of the main band associated with the low. Thus,
heavy rain with multiple inches of rain per hour rain rates are
expected through the Moderate Risk area. Soils in Louisiana and
Mississippi are already saturated now even before Days 1 and 2's
rains. While some parts of central Alabama have dry soils, that
should change as the soils are primed today/Day 1. Thus, by Day 3,
the entire Moderate Risk area should have well wetter than normal
soils. Thus, hydrology will play a big role in flash flood
development. For western areas, nearly constant heavy rain in Days
1-2 will make flooding into D3/Thursday very easy. Further east
into Alabama, the southerly flow of deep tropical moisture will
last longer as the low tracks eastward, so there will be a longer
period where heavy rain may be occurring over Alabama. In
coordination with BMX/Birmingham, AL forecast office, the Moderate
Risk was expanded east across central Alabama with this update.
Even once the low center passes, the air mass will be largely
unchanged behind the low, as the tropical air mass will still be in
place into the lower Mississippi Valley, thus, the low's cold front
could continue to produce storms into southern Alabama into
Thursday night.
...Ohio Valley...
The northern edge of the deep tropical air mass supporting the
tropical low to the south will bump up against a strong cold front
that will be set up along the Ohio River on Thursday. As the
plentiful moisture on southwesterly flow runs into the front,
training thunderstorms are expected through much of Kentucky,
particularly the southern half, Thursday afternoon and evening.
This could lead to a prolonged period of heavy rain due to training
and backbuilding thunderstorms over the region. For this reason, an
internal higher-end Slight was issued for the southern 2/3 of the
state. The Slight into the mid-Appalachians was trimmed on the
northern side around Pittsburgh, PA due to less moisture making it
that far north and east, and with the cold front over Kentucky
concentrating the storms further west, coverage of storms into West
Virginia also appears to have diminished in the guidance. Thus, the
Slight was dropped to a lower-end Slight.
At the western end of the front into southeastern Oklahoma and
parts of Arkansas, an MCS may develop late Thursday night as the
nocturnal jet intensifies. A Slight Risk was drawn in from far
north Texas along the MO/AR border to the Mississippi/Ohio River
confluence for expected slow-moving and training storms along much
of the front, though the highest concentration of storms should be
into southeastern Oklahoma.
Wegman

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt