Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
850 PM EDT Wed May 22 2024
Day 3
Valid 12Z Fri May 24 2024 - 12Z Sat May 25 2024

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES AND FROM
THE LOWER ARKANSAS/LOWER MISSISSIPPI VALLEYS INTO THE TENNESSEE
VALLEY AND SOUTHERN TO CENTRAL APPALACHIANS...

...2030Z Update...

No major changes to the southern Marginal across many of the same
areas as Day 2/Thursday...from northeast Texas to the southern
Appalachians. While this may be the 3rd straight day of storms for
some, convective coverage is expected to be lesser on Friday as
compared with previous days...such that despite the lower FFGs
likely to be in place, lesser coverage of storms should keep any
new flash flooding isolated.

The northern Marginal across much of the upper Midwest and Great
Lakes was expanded south to include Milwaukee and Chicago over to
the Quad Cities. The same low spreading rain further west Thursday
will move into this region on Friday. Much of Minnesota and
Wisconsin were hard hit yesterday with heavy rain, so some of these
areas may still be sensitive to heavy rain and resultant flash
flooding again on Friday, particularly if Thursday's rain in Day 2
overperforms.

For both Marginal Risk areas, confidence is not there for any
upgrades at this time.

Wegman

...Previous Discussion...

...Upper Mississippi Valley into the Upper Great Lakes...

The next strong area of height falls moving into the Northern High
Plains at the end of day 2 will continue to push eastward through
the Northern Plains and into the Upper Mississippi Valley during
day 3. The overall favorable large scale conditions ahead of these
height falls day 2 will continue into day 3 along the associated
front where strong frontal convergence in an axis of PW values 1 to
1.5 standard deviations above the mean will support potential for
moderate to locally heavy rainfall totals. This front does look
very progressive day 3, which may limit very heavy amounts. The
marginal risk was drawn to where there may be overlap of locally
heavy rains day 3 with heavy rains that have fallen over the past
24 hours.

...Lower Arkansas/Lower Mississippi Valley, Tennessee Valley into
the Southern to Central Appalachians...

A broad marginal risk area was maintained from the Lower
Arkansas/Lower Mississippi Valley region, east northeast across the
Tennessee Valley and into the Southern to Central Appalachians. PW
values across these regions will remain above average for the day 3
period, with additional shortwave energy moving west to east
supporting scattered convection and locally heavy rainfall
amounts. Not a lot of confidence in where the scattered convection
will become more organized, with a fairly large spread in model qpf
details.

Oravec