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FOUS30 KWBC 170047
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
847 PM EDT Mon Jun 16 2025

Day 1
Valid 01Z Tue Jun 17 2025 - 12Z Tue Jun 17 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE OHIO VALLEY AND MID-ATLANTIC STATES...

...Mid Atlantic...

Persistent convective pattern will remain over the region as
smaller mid-level perturbations ripple out out of the
Tennessee/Ohio Valley`s helping to generate rounds of showers and
storms as they migrate eastward. Antecedent conditions across
NC up through Southwest VA, much of WV, into Western PA are
incredibly moist with generally compromised soils over portions of
Eastern NC and the Central Appalachians. The one positive this
evening is the threat of heavy rainfall becomes less pronounced in
terms of magnitude as we slowly lose the diurnal heat element that
helps drive some of the stronger convective cores. In any case, the
threat remains for pockets of heavy rain that could exacerbate
already saturated grounds, preventing recovery. QPF maxima within
latest CAMs is generally 2-3", but no real defined area of interest
with a smattering of the heavier distribution. Highest probs are
within Central NC but >5" probs drop off steadily meaning the
threat is fairly capped ~3-4" with more likely 1-2" in convection.
The previous SLGT was generally maintained.

...Ohio Valley...

Our shortwave residing over the western Ohio Valley will aid in
maintaining a general convective pattern overnight with
thunderstorms pulsing up and down through areas surrounding the
Ohio River Basin down to the KY/TN line. Locally heavy precip has
already warranted a few flash flood warnings within KY and the
threat is forecast to continue migrating to the northeast over the
course of the overnight. Some areas could see a quick 2-4" of
rainfall in any of the strongest cells with some relatively slower
storm motions help enhance the threat for training within any
multi-cell clusters. Some of the latest hourly CAMs are insistent
on a threat of storms developing between Louisville and Cincinnati
overnight with some locally heavy precip over a more urban
corridor. Considering the trend, decided to pull the SLGT a bit
more northeast to cover for the threat as any cells overnight will
be capable of 1-2"/hr rates with multiple hours of impact. The
previous SLGT risk was adjusted to reflect the radar and proposed
forecast trends in the heaviest QPF alignment.

...Midwest and Plains...

Multiple complexes will propagate through portions of the Central
Plains and Upper Midwest this evening with the greatest potential
for flash flooding likely residing over more urban centers within
the span of the MRGL risk over the region. Faster forward motions
will limit some of the threat in any given area, as well as some
areas with higher FFG`s the benefactor of the expected heavy
precip. Flanking lines of complexes will be the areas of interest
within any of the organized convective schemes and pending where
they position themselves over the coverage area, a few flash flood
warnings cannot be ruled out. The previous MRGL was relatively
maintained, but trimmed back some of the northwest edge given radar
trends with no further heavy rain threat overnight.

Kleebauer


Day 2
Valid 12Z Tue Jun 17 2025 - 12Z Wed Jun 18 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CENTRAL APPALACHIANS AND THE CENTRAL PLAINS/MIDWEST...

...Central Appalachians to the Central Gulf Coast...
Broad SW mid-level flow downstream of an amplifying trough will
produce another day of active convection across the east-central
CONUS. As the SW flow amplifies, convectively charged shortwaves
embedded within the amplifying flow will surge northeast,
interacting with a residual front to produce a wave of low pressure
lifting into the Great Lakes Tuesday evening. Downstream of this
low, the front is likely to lift north as a warm front, aided by
return low-level flow around a ridge off the Southeast coast.
Together, these features will produce favorable thermodynamics and
kinematics for heavy rain producing convection.

Deep SW flow through much of the column from the Gulf Coast into
the northern Mid-Atlantic states will produce an environment
favorable to heavy rain producing thunderstorms from Louisiana to
Pennsylvania. Moisture will be high PW anomalies that reach above
+2 sigma across this swath. Widespread convective development is
supported in this environment 1"/hr rainfall likely. 12Z guidance
(and now the 18Z HRRR) has keyed in on central Pennsylvania as
having the greatest flash flood potential with a continued heavy
rain signal down to eastern KY. This is where the warm front will
focus more organized convection thanks to 35-45 kts of bulk shear,
which when combined with Corfidi vectors collapsing to 5-10 kts,
will result in a subtly enhanced repeating/training risk. This is
also where FFG is most compromised due to recent heavy rain events
(and more expected into this evening) which led to further
expansion of the Slight Risk, particularly in central Pennsylvania
where this can be considered a higher end Slight Risk. There is
potential for a targeted Moderate Risk to be drawn when the
confidence is there.

...Central Plains and Midwest...
12Z consensus continues SW trend in the 24hr QPF max with central
Kansas favored in the HREF mean. The HRRR, including now the 18Z
HRRR is more favoring south-central Kansas. This is from both
overnight activity tonight and the main event Tuesday night ahead
of the wave pushing onto the central Plains. The Slight Risk is
expanded across central Kansas to the Oklahoma border, as well as
farther north in Nebraska where the comma head will set up ahead of
the developing low. The threat of repeating heavy rain over
portions of Kansas warrants the Slight Risk to be considered higher
end with the potential for a moderate risk in subsequent issuances.


Weiss/Jackson


Day 3
Valid 12Z Wed Jun 18 2025 - 12Z Thu Jun 19 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MIDWEST, MID-SOUTH, GREAT LAKES, AND NORTHEAST URBAN CORRIDOR...

...Central States/Midwest...
A potent shortwave trough shifts northeast from Kansas to Michigan
on Wednesday. This feature will remain amplified through its
lifespan, interacting with a cold front across the Plains to drive
surface low pressure from northern Missouri Wednesday morning to
Lake Huron by the evening and enhance ascent through the track.
This lift will work with favorable thermodynamics for heavy
rainfall, with 1.75 to 2" PW (+2 standard deviations above normal)
and a ribbon of MUCAPE of 2000-3000 J/kg. This will support
widespread showers and thunderstorms, with hourly rainfall
exceeding 1 inch at times as storms move along the front. Storm
motions are likely to remain progressive much of Wednesday as 0-6km
mean winds are forecast to reach 30 kts, but repeating rounds are
possible as these winds track parallel to the front. This will
support stripes of heavy rainfall both with the comma head of the
upper low over Iowa/Wisconsin/Michigan, and in the warm sector over
Arkansas, southern Illinois, Indiana into Ohio. The Marginal Risk
was adjusted to depict a dry slot between these features.

...Northeast...
Broad southwesterly flow east of a trough axis over the Midwest
will pump Gulf-sourced moisture up the Eastern Seaboard. Global
guidance continues to depict a 2" contour of PW from northern
Virginia through southern New England which is around 2.5 standard
deviations above normal. Strong flow should maintain movement to
activity, but isolated heavy thunderstorms are forecast, so a
Marginal Risk is raised for the Bos-Wash megalopolis.


Weiss/Jackson


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt