049
FOUS30 KWBC 281556
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1156 AM EDT Sat Jun 28 2025

Day 1
Valid 16Z Sat Jun 28 2025 - 12Z Sun Jun 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTH-CENTRAL MISSOURI AND NORTH-CENTRAL ARKANSAS...


...Middle/Lower Mississippi Valley and adjacent southern Plains,
Ohio and Tennessee valleys...

Firmly in the warm sector and within a moist airmass containing
widespread PWATs of 1.8-2.2" (near the 90th climatological
percentile), isolated to scattered flash flooding is possible
today with a potentially higher focus across parts of southern MO
and northern AR tonight, where a Slight Risk of Excessive Rainfall
was introduced in the 16z update. An MCV evident on morning radar
and satellite imagery has already prompted a few FFWs across
eastern OK and KS while gradually pushing eastward. This feature
will aid in sparking widely scattered slow- moving thunderstorms
throughout the afternoon while instability levels rise due to
diurnal heating. Pulse thunderstorms within weak steering flow and
an unstable/moist environment are also likely through much of the
Ohio and Tennessee valleys today, with smaller scale scattered
flash flooding possible. Current trends are for the aforementioned
MCV to make it into the vicinity of southeast MO by late tonight
and influence a sharp mid-level trough ahead of increasing warm air
advection throughout the Plains due to a crossing shortwave in the
north- central U.S. and the nighttime low- level jet. CAMs still
differ somewhat in the exact location of a potential northwest-
southeast oriented band of slow-moving storms, but generally
converge on south-central MO and don`t really develop until around
09z tonight. The 12z HREF has increased 24-hr probs (12z Sat-12z
Sun) for greater than 5" of rain to 30-45% within the Slight Risk
outline. Additionally, this part of the country also has relatively
saturated soils already (70-100% 0-40 cm below ground relative
soil moisture percentiles per NASA SPoRT) not including the
likelihood of scattered thunderstorms and potentially overlapping
heavy rainfall this afternoon.

...Northern Plains and Upper Midwest...

Showers and thunderstorms capable of producing locally heavy
rainfall rates and heavy rainfall totals have the potential to
produce flash flooding as the next upper shortwave trough
approaches the north-central United States. Aided by a 90kt upper
level jet streak on the lee side...the upper trough will generate a
compact area of fairly robust, transient deep-layer forcing over
the outlook area later today and tonight. MUCAPEs are expected to
soar within the warm sector prior to the surface cold frontal
passage late tonight. Given precipitable water values getting near
1.75 inches...storms which form within the unstable airmass will
be capable of producing rainfall rates in excess 1.5"/hr and areal
average rainfall amounts of 1 to 3 inches...especially once low-
level inflow accelerates to between 30 kts and 40kts at 850 mb
ahead of the approaching front. The storm/mesoscale nature of the
threat leads to uncertainty of a more focused corridor of higher
risk, but a Slight Risk was considered in central MN where forward
propagation of storms may begin slow this evening and is reinforced
by the highest 12z HREF probs (20-30%) for exceeding 3" in 6 hours.

...Central Appalachians to the Northeast...

There continues to be a concern for heavy to potentially excessive
rainfall to develop across western Pennsylvania and surrounding
areas as the frontal boundary sags southward and taps into the
pooled PW values of 1.5-2". 12z CAMs are not a robust with rainfall
amounts in the central Appalachians and keep things moving along in
the Northeast to limit any flash flooding to isolated instances.
However, the environment remains unstable and moist, so any slow-
moving storms could lead to forming mesoscale boundaries that
create locally intense rainfall. Farther north, the Marginal Risk
was removed across northern New England given unimpressive radar
trends this morning and a more progressive patter. Still, 1-1.5" of
rainfall could lead to very isolated and more nuisance flooding.

...Southeast and central Florida Peninsula...

Scattered pulse thunderstorms are expected across a broad warm
sector and near an upper trough lingering over the region as
seasonable instability develops with daytime heating. A greater
focus for intense rainfall also overlaps with higher FFG across
the central Gulf Coast and Florida Peninsula, where rainfall rates
of 2-3"/hr are possible but should weaken quickly before
convection is driven off outflow from numerous other pop-up storms.

...New Mexico...

Yet another day of thunderstorms is expected across portions of
southern New Mexico and west Texas with locally heavy rainfall
(1-2") possible. QPF trends (coverage, intensity) are more isolated
compared prior days with the moist south to southeast low-level
upslope flow likely resulting in more localized areas of heavier
rainfall focused across the Sacramento and Guadalupe Mtns south
through the Trans-Pecos. The flash flood potential is expected to
remain isolated.

Snell

Day 2
Valid 12Z Sun Jun 29 2025 - 12Z Mon Jun 30 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL EXTENDING OVER
PORTIONS OF THE CENTRAL UNITED STATES...

There is a Marginal Risk of excessive rainfall over portions of
the central United States from the western Great Lakes south
through the Mississippi Valley and west into the central/southern
Plains and southern Rockies. Showers and thunderstorms are expected
both along and well-ahead of a cold front and trailing surface
trough/dryline as an upper-level trough approaches from the west.
Mechanisms to help focus convection becomes less defined ahead of
the front but deterministic guidance indicates widely scattered
rainfall totals of 1-3" are possible in an atmosphere characterized
by precipitable water values in excess of 1.5 inches over all but
the plains near the Central and Southern Rockies to in excess of 2
inches east of the Mississippi.

Waves propagating along the front may help to focus/organize
convection and lead to a more concentrated threat...and remained
supported by localized maxima in the ensemble means/probabilities
in the central Plains/Missouri Valley to the Upper Mississippi
Valley region...confidence remained low with respect to the exact
placement. Bann/Putnam

Bann

Day 3
Valid 12Z Mon Jun 30 2025 - 12Z Tue Jul 01 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE WESTERN PLAINS EASTWARD INTO THE MID ATLANTIC...

Similar to Sunday...convection is expected to develop within a region
of decent CAPE and precipitable water values in excess of 2
standard deviations above climatology. Except for some mid-level
westerly flow around the Great Lakes to provide some shear
there...the flow farther south should be fairly meager (but offset
by steeper low-level lapse rates). This sets up the potential for
some local rainfall rates in excess of 1 inch per hour that results
in excessive rainfall from the Western High Plains
east/northeastward into the Ohio Valley and parts of the Mid-
Atlantic region on Monday and Monday night. A weakening surface
boundary will help focus some of the threat for heavier rainfall
but its placement is quite uncertain. Without much forcing or
confidence in placement of a boundary to focus activity...placement
of any heavy rainfall is low confidence.

Bann


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