Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Sat Jun 20 2026
Day 2
Valid 12Z Sun Jun 21 2026 - 12Z Mon Jun 22 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FOR
PARTS OF THE CENTRAL PLAINS, MIDDLE MISSISSIPPI VALLEY, AND OHIO
VALLEY...

...Northern Missouri through central Illinois and Indiana...

By the start of the day 2 forecast period a potent shortwave and
related surface low/MCV are expected to eject eastward out of the
central Plains into the Midwest. There still remains at least some
uncertainty regarding the speed and latitude of these features
(NAM3k a northern outlier for example), but PWs and IVT above the
90th climatological percentile (per the 00z GEFS) overlapping with
soils likely still recovering from recent heavy rain in the Midwest
will likely lead to a swath of scattered flash flooding. A MDT
risk was introduced with the latest outlook, spanning from MO to
central IN. Heavy rain near a strengthening surface low and
increased lift along an eastward stretching warm front across the
Ohio Valley will overlap with saturated soils and swollen rivers
across much of IL and IN. This will be one axis for potentially
widespread flash flooding, with another axis lingering across
southwest MO into eastern KS and possibly a relative minimum in
between (right now most likely centered around central to
southeast MO). This MO/KS potential is associated with the
southwestern tail of an expected MCS, where flow may become
parallel to the outflow boundary/front and promote both training
thunderstorms and redevelopment of storms by Sunday evening.

NBM probabilities for at least 2" remain very high (between
70-90%) and cover much of northern MO, central IL, and central IN.
Locally higher totals (CAMs depict potential for 4-7" totals) are
likely given the convective environment. 00Z HREF and 18Z REFS
probabilities for exceeding 3-hr FFG are around 30-60% across IL
and IN, where antecedent ground conditions are wettest. The
progressive nature of these storms may end up limiting the severity
of flash flood impacts, but coverage of flash flooding impacts is
expected to be widespread enough in the Midwest/Ohio Valley to
warrant the level 3/4 MDT risk upgrade.

...Eastern Kansas to Southwest Missouri...

More information regarding the southern end of the Saturday night
thunderstorm complex/MCS likely to sink southeastward near a
trailing cold front and impact areas near the Ozarks Sunday. 850 mb
flow is expected to become quite convergent extending from central
KS to southern MO, which will likely be the focus for training
convection potential early on and then reforming activity later in
Sunday associated with additional shortwave activity moving
eastward across the Plains. However, there is some uncertainty
surrounding if this boundary can sink further south during the day
and keep storms somewhat progressive. This all combines for
guidance to currently depict current QPF amounts of 3-4" and an
average localized max of 6". This area also includes soils
saturated due to a recent wet weather pattern, with NASA SPoRT-LIS
depicting pockets above the 80th percentile in the 0-40cm soil
moisture layer. Lastly, 00Z REFS and HREF probabilities are
agreeable with 40-70% values for exceeding 3" per 6-hrs.

Snell


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