Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Wed Jul 9 2025
Day 3
Valid 12Z Fri Jul 11 2025 - 12Z Sat Jul 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MIDWEST...

...Midwest into Mid-Mississippi Valley...

20Z Update: Secondary vorticity maxima migrating through a
relatively low amplitude portion of the mid-level regime will eject
eastward in a similar path to the previous disturbance, only this
time encountering a more suitable environment with a deeper IVT
pulse being advected poleward ahead of the mean trough. A stronger
shortwave will also be digging south of out Canada allowing for a
better meridional push of deep layer moisture into the Upper
Midwest while also creating a more defined RER jet dynamic thanks
to a strengthening 250mb jet streak ~110kts positioned over the
Dakotas to Northern MN. Models have come into agreement on a west-
southwest to east-northeast oriented heavy convection regime with
some multi-cellular organization likely given increasing shear and
large scale forcing instigating the pattern. Totals between 2-4"
are being forecast already within the global deterministic with the
ensemble mean QPF firmly between 1-2" over a large area
encompassing Eastern NE, much of IA, Southern MN, and Western WI.
This correlates well with the forecast alignment of the stronger
IVT advection being pumped into the area due to the increasing
meridional state of the synoptic field. This setup has a pretty
robust indication via ML output as well, so the confidence has
grown enough to warrant a broad SLGT as the threat could be in
overlap of some hard hit areas the period prior. This will be an
evolving threat and the positioning of the risk could change in the
coming days, but wanted to align with consensus on initial
thinking.

Further south, a bit more complexity in the potential with less
agreement within the deterministic suite on potential heavy
convection across portions of MO/IL to the south of the pattern
evolving over the Midwest. Instability will be suitable overall,
but could be missing some elements to help push this threat to a
higher risk. Still, a fairly robust PWAT forecast and solid
thermodynamic structure should provide some modest risk for
isolated flash flooding, at a minimum. Maintained continuity of a
MRGL in the area to account for the potential and will be monitored
for targeted upgrade opportunities if the signal increases in
magnitude and/or coverage.

Kleebauer

...Mid-Atlantic and Southeast...

20Z Update: No changes necessary to the previous forecast as the
pattern remains favorable for isolated heavy rainfall across much
of the Southeast into the Southern Mid Atlantic.

Kleebauer

..Previous Discussion..

As mid-level troughing becomes more established in the Northern
Plains into Day 3, ridging builds in response downstream and may
finally begin to suppress convection more significantly across the
northern Mid-Atlantic into the Northeast. While there are no clear
signs of significant convective organization at this juncture into
the Southeast and southern Mid-Atlantic, convective initiation with
scattered convection and locally high rainfall rates appears likely
(where ridging will be insufficient to fully suppress convection).

Churchill

...Rockies into the Central and Southern High Plains...

20Z Update: A slightly better signal is being depicted across the
Front Range on Friday with a chance for a stronger convective
complex to initiate off the WY/CO Front Range and migrate east-
southeast along as the 850-300mb mean flow orients out of the
west-northwest in-lieu of a digging trough dropping out of Canada
to the north. A cold front trailing a surface low maturation over
the Central Plains would only entice a focal area for not only
heavy rainfall, but increasing prospects for back-building and
training behind any complex. The environment for locally enhanced
rainfall from any diurnally driven convection within a narrow lee
trough across the Southern High Plains and anticipated cold front
approach from the north will also lead to isolated flash flood
prospects from Southwest KS down into the Upper Trans Pecos. This
threat is on the lower end of the MRGL threshold, but still has
credence when assessing the overall environment. The MRGL will
remain in place from previous forecast, but will be keeping an eye
on perhaps a targeted upgrade in-of the migrating complex
anticipated off the Front Range.

Kleebauer

..Previous Discussion..

As the Southwest ridge continues to break down for a second day,
the global guidance signal for more substantial convective
initiation within the terrain of the Rockies increases into Friday
(and particularly so farther north into the northern/central
Rockies of WY/CO). Localized 1-2" totals (as indicated by both
downscaled deterministic GFS/ECMWF solutions and ensemble 1"
exceedance probabilities) in the sensitive terrain may lead to
localized flash flooding concerns, and more substantial convective
organization in association with shortwaves/vorticity maxima
rounding the ridge and coming off the terrain may allow for more
organized convection into the evening/overnight in the Central and
Southern High Plains.

Churchill

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt