FOUS30 KWBC 281352
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
952 AM EDT Tue Jul 28 2026

Day 3  Valid 12Z Thu Jul 30 2026 - 12Z Fri Jul 31 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE LOWER MISSOURI AND MID TO UPPER MISSISSIPPI VALLEY...

...Lower Missouri Valley into the Mid-Upper Mississippi Valley...
Shortwave energy will be progressing east southeast as it tracks
across parts of the central and northern plains on Thursday into
Thursday night/early Friday morning. The shortwave energy will be
encountering an increasingly moist and unstable airmass with
precipitable water values in excess of 2 inches being drawn into
the region ahead of the shortwave. Given the MCS/upscale growth
potential with this system, concentrated areas of heavy rain are
expected, especially across the Corn Belt. The Slight risk area
already issued for Thursday still covers the risk....especially
where the global ensemble probabilities of >3" in 12/24 hours are highest.

...Four Corners States into the Central/Northern Plains...
Monsoonal flow and anomalous deep-layer moisture will maintain an
isolated excessive rainfall risk extending from eastern Arizona
northeastward across much of western and northern New Mexico into
parts of Colorado. The expanding mid/upper level ridge will likely
limit the coverage compared to recent days.

...Central Gulf Coast Region into parts of the Southeast...
Heavy rainfall is expected along a front associated with a low
pressure system which will be pulling away from New England.
Heavy rainfall with some potential of flooding will be focused
along and near the front...especially over parts of Florida and Georgia line.

Bann
 

Day 4 and Day 5  Valid 12Z Fri Jul 31 2026 - 12Z Sun Aug 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FRIDAY ACROSS
PARTS OF THE MID AND UPPER MISSISSIPPI, AND ON SATURDAY OVER
PORTIONS OF THE LOWER OHIO VALLEY, TENNESSEE VALLEY, AND DEEP SOUTH...

...Mississippi Valley-Ohio Valley-Tennessee Valley-Deep South...
On Day 4 (Friday-Friday night), minor changes were made to
yesterday's Day 5 ERO, including refinements to the Slight Risk
area over parts of the Mid-Upper MS Valley, based on the latest
(00Z) global deterministic and probabilistic QPFs. The operational
models continue to show max 24hr totals in the 3-5" range,
particularly over IA-southeast MN-southwest WI, though again with
some spatial spread in the guidance. 00Z Operational ECMWF has a
bit more areal coverage of the 3+ inch totals, while the ECENS QPF
exceedance probabilities have once again come up from the previous
run. Based on the latest guidance, along with the most recent ECMWF
EFI output (EFI values aoa 0.6), have nudged the southern portion
of the Slight Risk area a little farther north across the Mid MS Valley.

On Day 5 (Saturday-Saturday night), the globals continue to show a
fairly vigorous 500 mb trough/embedded shortwave energy slowly pivoting
into the Mid MS Valley. There isn't as strong of a signal in the
QPF guidance compared to the previous couple of days; however, the
amplifying upper level trough (favorable Qs forcing and increasing
effective bulk shear) will combine with a favorable thermodynamic
profile (ML CAPEs 1000-2000 J/Kg along a swath of 1.8-2.1" PWs) to
generate organized heavy rainfall threat across western portions
of the Lower OH Valley into the TN Valley and perhaps as far south
as southern AL, depending on how far south the upper shortwave and
favorable 0-6KM bulk shear can get. Concern within this area will
be heavy rainfall rates (2+ in/hr) given the thermodynamic profile,
along with the potential for cell training of convection as the
upper shortwave begins to stall and the low-level inflow out ahead
of it increases up and aligns more parallel to the mean 850-300 mb
flow. Because of these factors, we felt that a Slight Risk was warranted.

...Four Corners States into the Southern-Central High Plains...
Monsoonal flow and anomalous deep-layer moisture will maintain a
Marginal (isolated) excessive rainfall risk over eastern AZ and
much of NM into much of CO. The expanding mid/upper level ridge
(600dm heights at 500 mb) will likely limit the coverage compared
to recent days, especially on Friday.

...Central Gulf Coast Region into parts of the Southeast...
Heavy rainfall is expected along the New England cyclone's trailing
front near the FL/GA border, the front that will become more
quasi-stationary Thu-Fri before lifting lifting back north on Sat
ahead of the approaching upper trough. Deep-layer moisture and
instability should be more than sufficient and the guidance shows
sufficient effective bulk shear (0-6km magnitudes generally over 20
kts) for more organized/persistent convective organization. As a
result, have maintained the inherited Marginal Risk on Day 4 (Fri-
Fri night), with a similar Marginal Risk area on Day 5 (Sat-Sat night).

Hurley
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