Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
359 PM EDT Thu Mar 13 2025
Day 2
Valid 12Z Fri Mar 14 2025 - 12Z Sat Mar 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE LOWER TO MID MISSISSIPPI VALLEY INTO PARTS OF THE OHIO AND
TENNESSEE VALLEYS...

...2030Z Update...

Prior discussion reviewing the synoptic setup and caveats on the
more limited potential for a flash flooding threat compared to a
severe threat remain on track. Expect a line of convection to
develop along the cold front by early evening, first for more
northern areas across the Middle Mississippi Valley with additional
storms extending southward through the Lower Ohio and Tennessee
Valleys through the night. Updated 12Z hi-res guidance indicates
the combination of strong dynamics, moist southerly return flow,
and sufficient instability could lead to some locally heavier
rainfall amounts around 2" supported by quick downpours with rain
rates of 1-1.5" per hour. However, this potential appears to remain
rather limited given the quick progression of the storms/cold
front, and thus only a few isolated instances of flash flooding
mainly for urban areas is expected.

Putnam

A strong mid-to-upper level shortwave crossing the Southwest on
Day 1 is expected to move east of the Rockies, with a negatively-
tilted low developing over the central Plains early in the period.
Powerful forcing is forecast to interact with what is expected to
be a relatively modest plume of moisture advecting north ahead of
the system. Storms are forecast to develop initially over the lower
to mid Mississippi Valley Friday afternoon before moving east into
the Tennessee and Ohio valleys during the evening and overnight.
Cell motions will likely be quite progressive given the very strong
wind fields in place. Therefore, this convection will likely pose
more of a severe risk than a flash flood threat. However, given the
strong dynamics, along with sufficient instability for deep
convection, expect that rainfall rates will be briefly intense
enough to produce localized amounts that exceed current model
forecasts (maybe locally over 2 inches). Still, this appears to be
a lower-end flood threat, and probably confined to localized
impacts over more sensitive urban or low lying areas that are
impacted by a quick burst of intense rainfall.

Pereira

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