Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 PM EDT Mon Jun 3 2024
Day 2
Valid 12Z Tue Jun 04 2024 - 12Z Wed Jun 05 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE PLAINS AND MISSISSIPPI VALLEY...

21Z update... The southern periphery of the Slight Risk area was
expanded further south/southwest into portions of Oklahoma and
Texas. QPF trends suggests an additional 1 to 3 inches focused over
much of the same area drenched during the day 1 period. Rivers and
streams are already running higher, especially near the Red River
Valley, and the additional precipitation will maintain an elevated
risk for flash flooding concerns.

Campbell

Another system moving into the Plains will bring a heavy rainfall
risk Tuesday into Tuesday night. Pretty strong large scale forcing
expected from IA into MN with a sharp mid level trough and plenty
of shortwave and upper jet energy to work with. Most indications
are that the front and convection will be progressive in nature,
which should end up limiting the upper bound potential of rainfall
totals. Just looking at this quick motion and model QPF fields
would probably suggest this is more of a Marginal risk type of
threat. However antecedent conditions will be quite wet over a lot
of this corridor...with streamflows and soil saturation levels
running much above average for the time of year. Thus flash flood
susceptibility will likely also be higher than normal...which
combined with higher PWs than this past event...suggests some flash
flood risk exists and the Slight risk remains warranted.

Large scale forcing drops off some as you go south into
KS/MO/OK/AR...however stronger instability and low level moisture
convergence expected here as the front aligns itself a bit more
west to east. These factors support some potential
training/backbuilding of convection for a period of time...although
even here the overall pattern is progressive. Tend to think the
higher QPF magnitudes will end up here, which combined with areas
of wet antecedent conditions, warrants a Slight risk.

The biggest change with this issuance was a large expansion of the
Marginal risk into more of the OH/TN valley into the Southeast and
southern Mid-Atlantic. The convective forecast is of low
predictability over these areas, but note some rather high QPF
output in several models, including the 00z GFS, GEM reg and UKMET.
These higher QPF values appear to be in part related to a
convectively enhanced shortwave that is expected to eject out of
the Plains Monday night and into this region Tuesday. This feature
should help organize a convective threat over this region...and the
setup does have some potential for a more organized flash flood
risk and potential category upgrade in the ERO. However this will
at least partially depend on how Plains convection Monday night
evolves and impacts the subsequent convectively enhanced shortwave
that is expected to move into the TN/OH Valley Tuesday.

The southern extent of this Marginal risk closer to the Gulf Coast
is more of a conditional risk. Some of the HREF members, including
the 06z HRRR, suggest an organized convective complex may move
into this area Tuesday morning.

Chenard