Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
817 PM EDT Sun May 17 2026
Day 2
Valid 12Z Mon May 18 2026 - 12Z Tue May 19 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL
PLAINS TO THE UPPER MISSISSIPPI VALLEY...

.19Z Update...

The forecast remains on track with another round of heavy rainfall
expected to impact areas from the central Plains to the Upper
Mississippi Valley where a high-end Slight Risk area remains in the
outlook. The highest flash flood risk looks to focus over portions
of northern Kansas and Missouri and southern Iowa and Nebraska
where backbuilding/repeating storms will be favored. Soils in this
area will be thoroughly saturated from rainfall during the Day 1
period, which will increase sensitivity to additional rainfall.
Storms will likely produce rainfall rates of 2 inches per hour and
could exceed 3 inches per hour, which would exceed flash flood
guidance for this area.

Dolan

.Previous Discussion...

Relatively few changes were needed to the outlook for this likely
busiest day of the upcoming three. A strong shortwave making up the
base of the longwave trough over the Rockies will finally eject out
over the Plains on Monday. As that shortwave interacts with
plentiful Gulf moisture streaming north up the Plains, renewed
lines of showers and storms are expected to develop across the
Slight Risk area. Since the storm motion will be towards the
northeast, largely parallel to the moisture and instability plume
emanating from the Gulf, backbuilding will be a greater
possibility than in previous days. Several of the high resolution
model guidance show that there could be multiple rounds of storms
to impact the area from northeast Kansas through southwestern Iowa,
especially in the late afternoon through the first half of the
overnight. This area is currently getting very hard-hit with heavy
rain from a very slow-moving MCS that has been producing multiple
inch per hour rainfall rates and numerous instances of flash
flooding. Thus, the soils have become very saturated in some areas.
Following potential heavy rain during the day 1/Sunday period,
much more rain is expected in this region again on Monday. A
higher-end Slight covers the aforementioned region from northeast
Kansas through the southwest corner of Iowa. Should multiple inch
per hour rates materialize again in this same region, a Moderate
Risk upgrade will need to be considered with future updates.

Wegman

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