Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
407 AM EDT Tue Sep 15 2026
Day 1
Valid 12Z Tue Sep 15 2026 - 12Z Wed Sep 16 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
NORTHEASTERN KANSAS INTO NORTHWEST MISSOURI...

...Central U.S...

Current setup for Tuesday into early Wednesday morning continues to
look active with a prominent isentropic ascent pattern across
portions of the nations mid-section with the focus across the
Missouri River Valley between KS/MO and the southeastern corner of
NE. Cold front analyzed over NE will slide southeastward and fan
out as it migrates southward as it begins to feel the influence of
the ridge dominating the weather pattern over Mid-Mississippi
Valley and points south. Steady frontal progression will lead to
the front positioned over central KS and MO by the afternoon and
early evening hours with a sharp theta_E gradient pattern arising
just north of I-70. Aloft, a shortwave ejection out of the Central
to Southern High Plains will pivot northeast around the western
periphery of the broad upper ridge situated over the Southeast
leading to ample mid and upper level forcing to coincide with a
modestly unstable and moisture rich environment. PWAT anomalies
between +2 to +3 standard deviations are forecast across much of KS
into MO with values around 2" likely for areas along and south of
that established theta_E gradient. Mean flow aloft will run
relatively parallel to any front/boundary bisecting the area
leading to storm motions that will track generally west-southwest
to east-northeast after initiation. Best chance for convective
initiation will occur late-afternoon through the evening with the
evening and overnight time frame the most susceptible period for
heavy rain and flash flood concerns as LLJ influence allows for
fresh low-level moisture injection and a bit more low-level shear
to maintain mesocyclone maintenance.

Latest CAMs and associated HREF output at 00z this evening
indicated a wide swath of 2-3" areal average mean with the blended
mean guidance upwards of 3-5" over the area of northeastern KS
through much of northwestern MO. There's a growing consensus in the
heaviest rainfall occurring just north of Topeka to points
northeast, including areas like St. Joseph, Missouri, as well as
neighboring counties that have seen significant rainfall as
recently as this past morning causing localized flash flooding to
occur prior to the event. Areal FFG's for the 1 and 3-hr intervals
lean lower than normal with typical thresholds around 1 to 2
inches, respectively for the exceedance times referenced. HREF
probs for >1"/hr rates are running between 40-70% for several hrs
across the northeastern corner of KS into northwest MO which would
enhance the threat of FFG exceedance, matching the modest 3hr FFG
exceedance probabilities off the last succession of HREF runs. The
threat for heavy rain is also further south, closer to the expected
frontal positioning with areas along I-70, including the Kansas
City metro potentially seeing the heavy rain prospects that could
invoke flash flooding. The probabilities are more aligned for the
areas to the north, but there is a noted shift south from the
previous run of slightly better chances to the metro area, so want
to make reference given the setup is conducive for prolonged heavy
rain chances and some locally significant totals.

In coordination with the local WFO's in Topeka and Kansas City, a
Moderate Risk was added to the latest D1 update encompassing the
northeastern counties in Kansas, extending northeast into portions
of northwest Missouri. The MDT also clips the far southeast corner
of Nebraska along the Missouri River to reflect the higher
probabilities also situated in that area. A high-end SLGT is
forecast for the surrounding areas of northern MO and northeast KS,
down into the I-70 corridor in both states. This also encompasses
the entire Kansas City metro, reflecting the potential of heavy
rain and higher impacts extending further south. The SLGT extends
south through the High Plains along the cold front progression
occurring further west, especially southwest of I-35. SLGT extends
northeast into the Midwestern areas to account for heavy rainfall
chances occurring later this morning, and then another for the
following evening.

...Southwest...

The Southwest CONUS will remain active with a multitude of small
shortwave perturbations rounding the western periphery of the broad
ridge positioned over the Southern U.S, entering into the region
with PWAT anomalies firmly +2 or greater across eastern AZ into NM
and southern CO. Models continue to pinpoint areas of northern and
western NM as the beneficiaries of the setup with a secondary focal
point now encompassing the central and eastern sections of the
Mogollon Rim. Latest HREF mean QPF signals a solid 0.5-1" output
over the two main areas of concern with individual deterministic
outputs upwards of locally 2-3" in the hardest hit locations.
Neighborhood probabilities between 40-70% for >2" confirm the
individual ensemble members within the CAMs suite which would lead
to another scattered flash flood concern in-of the terrain
outlined. A broad SLGT remains positioned over the aforementioned
areas with an emphasis on eastern AZ and the western half of NM.

Kleebauer


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt