Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Tue Oct 13 2026
Day 2
Valid 12Z Wed Oct 14 2026 - 12Z Thu Oct 15 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHERN HIGH PLAINS INTO THE CENTRAL PLAINS, AND THE MID-
MISSISSIPPI AND OHIO VALLEYS...

A generally classic setup for persistent heavy rainfall will
materialize over the Central and Southern U.S. come mid-week with a
vast, arcing jet situated from the Central Rockies to the Canadian
Maritimes. At the surface, a slow-moving area of low pressure with
attendant frontal alignments on both the eastern and southern flank
of the surface center will meander over the Front Range and Central
Plains with the cold front at the trough base making headway
through the Southern Rockies into the Southern High Plains by the
end of the forecast cycle with a press of Pacific air in wake of
the front. The front over the Southwest is anticipated to lose some
steam in its progression to the east leading to less propulsion
into the High Plains, but enough to garner at least another viable
region of convergence across far west TX up through the Caprock of
TX. Further north, the front in question will become more quasi-
stationary with its forward propagation likely coming from local
outflows and the leading edge of the pressure gradient caused by a
strengthening areas of surface high pressure over the Northern
Plains. As our upper level disturbance makes its advancement into
the Central Rockies on Wednesday evening, we'll finally see the
overall pattern begin to exhibit more motion with front over the
Plains being pushed south with the surface ridge to the north
shifting eastward into the Great Lakes and strengthening slowly
thanks to the evolution of the upstream upper level pattern.

The combination of large scale ascent situated under a broad RER
of a prolific upper jet along with ample moisture advected up out
of the Gulf and from some of the remnants of now Hurricane Simon
being pulled poleward will create a broad convective regime with
general QPF maxima occurring during peak diurnal instability and
overnight when the nocturnal LLJ initiates over the Plains. There
continues to be excellent consensus among all guidance, including
the latest CAMs this evening, for a prolonged heavy rain event
from southwest TX up through the Mid-Mississippi Valley, arcing as
far east as the Ohio Valley along the front positioned on the
leading edge of a strong surface high moving over the northern tier
of the CONUS. Forecast PWAT anomalies maintain a consistent
depiction among both the deterministic and ensemble based outputs
with the latter converging on a widespread area of +2 to +3
standard deviations over much of the Central and Southern U.S. into
the western Ohio Valley. The latest CAMs are ripe with a large
area of convective coverage throughout the D2 over this broad
expanse of the CONUS as the upper level projection maintains such a
stable presence of robust upper forcing with the upper jet fixed
over the same area for at least 36-48 hrs. This has led to signals
for 1-2" rainfall potential with locally higher inputs within the
deterministic across the Ohio Valley into the Mid-Mississippi area,
and closer to 2-3" means across the Southern Plains back into west
TX where the greatest instability, deep layer moisture presence,
and added mid-level energy advection are co-located for the setup.

Just based off the first 12 hrs in the forecast cycle (12z Wed -
00z Thu), the 00z HREF neighborhood and EAS probabilities signal
modest threats for totals >2" with a core of relevant >3" probs
located across western OK down into the Red River area along the
TX/OK border. This is prior to even the threat that will occur in
the evening with the additional LLJ presence that will surely prop
up the convective potential and allow for prolonged spells of
heavy rainfall along and ahead of the quasi-stationary front turned
cold front Wednesday night into Thursday morning. Areas from west
TX up through OK into the Ozarks are likely to be the beneficiaries
from this evolution as the front becomes a focal point for
convection, and will continue to be the case as we move into the
new D3. The previous SLGT risk was not only maintained, but
expanded further east into the Central and Southern Ohio Valley
with an emphasis along the Ohio River basin where models are keen
to heavy precip prospects during the afternoon and evening hours
Wednesday. The SLGT expands through much of the South-Central
Plains, and back into the Southern High Plains where scattered
thunderstorms with heavy rainfall are increasingly likely come
Wednesday evening as the environment remains buoyant and
sufficiently moist for stronger convective cores capable of rates
>2"/hr at times.

Kleebauer


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