Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Feb 27 2023 07:21:58

FOUS30 KWBC 270721
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
221 AM EST Mon Feb 27 2023

Day 1
Valid 12Z Mon Feb 27 2023 - 12Z Tue Feb 28 2023

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN GREAT LAKES AND UPPER OHIO VALLEY...=20
=20
A strong low pressure system moving through Iowa will begin to
weaken as the upper-level shortwave shears out while rounding the
top of an anomalous Southeast ridge. Ongoing convection associated
with a previous MCS ejecting out of the central Plains should be
entering Illinois Monday morning. Potent moisture flux along a
strong low-level jet into the Great Lakes and Ohio Valley will
support a marginal heavy rainfall threat. Precipitable water
values should nose upward to at or above 1" -- 2-4 sigmas above
the mean for late February per the NAM guidance -- while the
better moisture slides eastward into the Upper Ohio Valley by the
early evening. MUCAPE values are expected to reach up to 500 J/kg.
 Maximum rainfall amounts across the Marginal Risk area could
locally reach up to 2" if redeveloping convection overlaps
previous rainfall throughout the Ohio Valley by early evening.=20
Soils have been saturated by 300-600% of average rainfall during
the past week across portions of northern IL, southeast WI, and
the southern Mitt of MI.  However, this remains a low chance due
to the overall quick system progression/limited residence times of
the better ingredients, thus the Marginal Risk designation. These
totals suggest only minor and localized flooding is possible as
opposed to more scattered flooding concerns, with ponding water
and rapid runoff most likely over areas around the Great Lakes
where recent snowmelt also comes into play.=20
=20
Roth/Snell


Day 2
Valid 12Z Tue Feb 28 2023 - 12Z Wed Mar 01 2023

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.=20

Roth


Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!-tCVDr1A5_7ZJUR9jphcckFyB2bGGk4mwYIyqQOAtyOO=
mUu-_aqC-0ti0uc1jl-ZUtnzyVbYf1elaVaQMkf9YLDhsd4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!-tCVDr1A5_7ZJUR9jphcckFyB2bGGk4mwYIyqQOAtyOO=
mUu-_aqC-0ti0uc1jl-ZUtnzyVbYf1elaVaQMkf9UQBLbeI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!-tCVDr1A5_7ZJUR9jphcckFyB2bGGk4mwYIyqQOAtyOO=
mUu-_aqC-0ti0uc1jl-ZUtnzyVbYf1elaVaQMkf9BV0diuo$=20


$$



=3D =3D =3D
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