Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
931 AM EDT Mon May 20 2024
Day 2
Valid 12Z Tue May 21 2024 - 12Z Wed May 22 2024

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

A strong vort ejecting northeastward on the eastern side of the
amplifying Rockies trof late day 1 into day 2 will become
increasingly negatively tilted as it pushes northeast across the
Central Plains into the Upper Mississippi Valley. This will help
deepen surface low pressure across the eastern portions of the
Central Plains early day 2, moving northeast into the Upper
Mississippi Valley/Upper Lakes region later day 2. There is pretty
good consensus for an axis of heavy comma head/deformation precip
from far eastern South Dakota, across large portions of Minnesota
and northern Wisconsin. Consensus is for two well defined areas of
precip to push northeastward across the Upper Mississippi Valley
into the Upper Lakes, comprised of a comma head/deformation precip
area on the northwest side and a more progressive convective
precip area on the southeast side. Similar to day 1, the expected
progressive convection on the southeast side of this system will be
a detriment to very heavy totals, while slower moving/pivoting
comma head precip should support potential for heavy total rainfall
amounts, although rates may not be very high. Stream flows as per
the National Water Model, remain high where the heavier comma
head/deformation precip is expected and correspond to the slight
risk area. There were only some minor changes made to the previous
slight risk area, decreasing it on the southeast side over
southeast Wisconsin into northeast Illinois where the convective
events are expected to be progressive.

Oravec