FOUS30 KWBC 190750
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Sat Jul 19 2025

Day 1
Valid 12Z Sat Jul 19 2025 - 12Z Sun Jul 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF 
THE MIDWEST, THE MID-SOUTH, THE SOUTHERN MID-ATLANTIC STATES, & 
THE SOUTHERN APPALACHIANS...

Corn Belt/Ohio Valley/Mid-Atlantic States/Mid-South...
Ample moisture exists regionally. Some of this is due to the 
synoptic pattern, with the Westerlies stronger than and south of 
July norms which is allowing for greater effective bulk shear and 
thunderstorm organization. Some of the moisture influx is also due 
to the flow around the retrograding 3 sigma warm core ridge for 
mid- July moving into the eastern Gulf. Additional moisture is 
being imported from the direction of the former tropical 
disturbance. Regardless of the source, precipitable water values 
are forecast to crest at or above 2.25". ML CAPE could exceed 4000 
J/kg due to daytime heating. Portions of IA, IL, and KY have the 
potential for backbuilding convection both Saturday morning and 
Saturday night/Sunday morning. Across IA, there is a question about
how much overlap convection dropping in from the north this 
morning would have with convection Saturday night/Sunday morning. 
Within such an environment, hourly rain amounts to 4" are possible,
with local amounts to 8". At the moment, these amounts are not 
explicitly forecast by much of the guidance, with the 00z HREF/18z 
RRFS showing minimal potential for 5"+ amounts, centered across IA.
However, the high resolution NAM and Canadian Regional show local 
totals in the 6" ballpark. Large swaths of the region have had 
well above average rainfall during the past week, saturating soils.
Since there's a bit of uncertainty, coordination with DMX/Des 
Moines IA and DVN/Davenport IA have left the risk area as a high- 
end Slight. However, should cells train for 2+ hours downstream of 
existing instability pools, localized Moderate or High Risk 
impacts cannot be ruled out.

Southwest/Southern Rockies...
Enough moisture is available for scattered monsoon convection again
on Saturday. Hourly amounts to 2" are possible due to diurnal
heating, which would be most problematic in urban areas, dry
washes/arroyos, or burn scars.

Roth


Day 2
Valid 12Z Sun Jul 20 2025 - 12Z Mon Jul 21 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MIDWEST, SOUTHERN APPALACHIANS, & NORTHERN PLAINS...

...Midwest, Ohio Valley, & Southern Appalachians... 
High moisture for Saturday persists into Sunday -- precipitable
water values eclipsing 2.25" -- with the core of the instability 
pool more significant across portions of the Ohio Valley on Sunday 
as warming at 700 hPa occurs across the Central Plains, slowly 
strengthening a mid-level capping inversion. Effective bulk shear 
should remain sufficient for convective organization. Inflow off 
the instability pool could lead to backbuilding, so the potential 
for 4" amounts in an hour and local 8" totals remains (the 00z NAM 
advertised 7". There's not enough confidence on where the higher 
amounts will materialize to upgrade to a Moderate Risk, but a 
higher end Slight Risk appears to exist from in and near southern 
IL into KY, TN, southern WV, and westernmost VA. Localized Moderate
or High Risk impacts cannot be ruled out.

...Northern Plains...
Much of North Dakota will be at the nose of a potent low level jet
across the area. A subtle shortwave in the upper level jet may be 
all it takes to initiate a line of storms across the region, 
though there may be two separate rounds: one in the morning and a 
second Sunday night. There is considerable uncertainty both with 
storm intensity and receptivity of the ground to the heavy 
rainfall. Used the recent guidance to trim some of the Slight Risk 
area away. Like continuity, believe this is a lower end Slight Risk.

Southwest/Southern Rockies...
Enough moisture is available for scattered monsoon convection on
Sunday. Hourly amounts to 2" are possible due to diurnal heating, 
which would be most problematic in urban areas, dry washes/arroyos,
or burn scars.

Roth/Wegman


Day 3
Valid 12Z Mon Jul 21 2025 - 12Z Tue Jul 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF 
THE SOUTHERN ROCKIES, PLAINS, OHIO VALLEY, & SOUTHEAST...

Surface boundaries/low pressure areas/upper level disturbances are
on this move this period, which along with warming temperatures at
700 hPa/increased mid- level capping across portions of the 
Central Plains and IA should broadly limit QPF and flash flood 
potential. Wherever cells can manage to train/merge, hourly rain 
amounts up to 3" with local totals to 6" would be possible across 
the Plains, Ohio Valley, and Southeast, while hourly amounts up to 
2" and local totals to 4" would be possible across the Southern 
Rockies and Southwest. At the moment, it appears any flash flooding
would be on an isolated to widely scattered basis. In the 
Southwest and Southern Rockies, burn scars and dry washes/arroyos 
would be most at risk. Anywhere within these regions, urban areas 
would be of most concern.

Roth

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