Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
423 AM EDT Fri Apr 26 2024
Day 1
Valid 12Z Fri Apr 26 2024 - 12Z Sat Apr 27 2024

...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS ACROSS PORTIONS OF
THE SOUTHERN PLAINS INTO THE LOWER TO MIDDLE MISSISSIPPI VALLEY...

A Slight risk was maintained with this update from portions of
northeast TX into MO, although there remains some uncertainty
regarding the intensity and organization of this activity.
Convection will likely be ongoing at 12z this morning across
portions of TX and OK, with this activity gradually pushing
eastward across these two states and into portions of MO and AR
through the afternoon hours. With time today the better synoptic
forcing lifts to the north, resulting in a downward trend in
forcing across the southern half of the Slight risk, with
weakening lower level convergence and also less pronounced
mid/upper level ascent. These larger scale factors would generally
favor weaker and less organized convection with time today into
tonight over these southern areas. Countering this is a rather
favorable thermodynamic environment, with plentiful instability and
moisture. Thus it seems most likely that if convection this
morning over OK and TX can grow upscale enough to generate an
organized outflow/cold pool, then this mesoscale feature could be
enough to sustain an axis of more robust convection through today.
Any convection that is able to sustain and grow upscale may exhibit
some training and backbuilding characteristics into the strong low
level jet in place. More recent observational and HRRR trends
suggest portions of MO have the best chance of seeing multiple
convective rounds today with stronger upper forcing and WAA...with
one round this morning and another through the afternoon hours.
Thus we did expand the Slight risk into more of MO to account for
this risk.

Further north a Marginal risk is in place from northern MO into SD
and MN. Elevated showers and embedded thunderstorms will move
across this region this morning, but will be outrunning the better
instability...which should keep rainfall rates low enough to
prevent any more organized flood threat. As the surface low and
strong mid/upper forcing ejects into the Plains this afternoon
additional convective development is likely from eastern NE/SD into
portions of IA and MN. Some of this activity should be intense,
but generally should be moving at a quick enough pace to limit the
flash flood risk.

Chenard