FOUS30 KWBC 300828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Thu Jul 30 2026

Day 1
Valid 12Z Thu Jul 30 2026 - 12Z Fri Jul 31 2026

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

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 today into 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 ahead of the shortwave.
Model guidance still reflected an increased risk for excessive
rainfall over portions of Arkansas and the outlook area was largely
left unchanged in this cycle. Concentrated areas of heavy rain are
expected given the potential for training and repeat- convection.
The Slight Risk remained in good shape and only minor adjustments
were needed.

...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 during the afternoon and evening hours.

...New England...
A low pressure system located along the southern New England coast
at the start of the outlook period will take a turn to the
northeast and head out to sea later today. Locally heavy rainfall
will remain possible across the region given its proximity and
ample moisture to work with. While the instability will likely be
less compared to Tuesday/Wednesday, the stronger dynamics at play
and potential for training rainfall could lead to a localized
threat, particularly if over areas more saturated from previous
rainfall. A Marginal Risk was maintained.

Bann
 

Day 2
Valid 12Z Fri Jul 31 2026 - 12Z Sat Aug 01 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FRIDAY ACROSS
PARTS OF THE UPPER MIDWEST TO MID MISSISSIPPI VALLEY...

...Central US system...
Shortwave energy initially moving eastward out of the Northern
Rockies and adjacent High Plains will be accompanied by showers and
thunderstorms as the Day 2 period begins at 12Z on Friday. The
system will start taking a southward track in response to upscale
ridging across Montana and nearby areas of southern Canada. The
placement of the Marginal and Slight risk areas were similar to the
previous outlook and saw little reason to stray far from the
adjustments that were made on Wednesday because there was still
good agreement with where the synoptic scale forcing will be
greatest. The southern portion of the Marginal risk area remained
closer to the placement of greater instability which would support
higher intensity rainfall rates. Any downpours across that region
may at least have a chance at challenging the flash flood guidance.

...Central Gulf Coast Region into parts of the Southeast...
Locally heavy to excessive rainfall remains possible along and near
an east to west oriented quasi-stationary front. 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, no changes to the Marginal Risk area
already issued.

...Four Corners States into the Southern-Central High Plains...
Monsoonal flow and anomalous deep-layer moisture will keep the
potential for isolated instances of excessive rainfall across
portions of eastern AZ and much of New Mexico into Colorado. The
areal coverage may be less than in preceding days given the
expansion of the sprawling upper ridge.

Bann
 

Day 3
Valid 12Z Sat Aug 01 2026 - 12Z Sun Aug 02 2026

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE OHIO AND TENNESSEE VALLEYS...

Ohio and Tennesee Valleys To Parts of the Southeast US...

The transport of moisture northward from the Gulf will only
increase on Saturday ahead ofan amplifying mid- and upper-level
trough approaches from the west. This sets up the possibility for
heavy to excessive rainfall from parts of the Ohio and Tennessee
Valley and southward into the Southeast states from Saturday to
early Sunday morning.  The spread in model deterministic QPF and
from the ensemble neighborhood probability of exceedance plots
remained large...which seemingly led to only modest QPF amounts in
blended QPF solutions. With the mid-level wave approaching 2
standardized anomalies and the precipitable water still forecast to
be in the 2 to 2.25 inches range...think there is more potential
for heavy rainfall than not. Expanded the Slight Risk area
southward but not to the point where the 1- and 3-hour flash flood
guidance exceeds 4 inches per 3 hours.

...Four Corners States into the Southern-Central High Plains...
Monsoonal flow and anomalous deep-layer moisture will persist over
much of the Four Corners region and adjacent areas. Once
again...WPC maintained a Marginal excessive rainfall area here
without much change in coverage due to forecast reasoning remaining the same.

...Central Gulf Coast Region into parts of the Southeast...
Heavy rainfall threat will continue over this region along the
southern periphery of the full-latitude trough, south of the
quasi-sationary front. Deep-layer moisture and instability should
be more than sufficient, especially when coinciding with the weak
upper forcing (upstream upper trough w/ embedded convectively-aided
shortwaves), for more organized/persistent convective organization.

Bann
 

Day 4 and Day 5
Valid 12Z Sun Aug 02 2026 - 12Z Tue Aug 04 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHEAST
PENNSYLVANIA INTO NORTHERN NEW YORK STATE...

An axis of anomalous PW likely along and ahead of the cold front
expected to push out of the eastern Lakes into the northeast in the
Sunday to Monday time frame. There is the beginning of model
divergence with the evolution of the upper trof and the details of
how the trof splits into northern and southern components,
affecting the timing in the models with the eastward push of the
front and the associated precip. However, overall favorable upper
dynamics in the anomalous PW axis should support active convection
along and ahead of this front, with potential for a period of
training in the moist low level southwest flow parallel to the
front. A slight risk was introduced for heavy rain potential that
may fall across areas with reduced FFG values from the recent very
heavy rainfall amounts from northeast PA into northern NY State.

For both day 4 and day 5...a marginal risk was depicted for
monsoonal convection across southern Arizona into southwest New
Mexico. Not a lot of confidence with qpf details here, but locally
heavy rains and isolated runoff issues possible in the above
average PW values expected across this area.

By day 5...there are more significant model differences with the
evolution of the upper trof across large portions of the east. The
GFS is keeping the southern component of this trof stronger and
farther north than much of the other guidance and has a more
significant heavy rain foot print from NC into southern New England.
While confidence is low with any one solution, there is still
potential for heavy precip in the anomalous PW axis that will
continue ahead of this upper trof. Some of this may fall across
portions of southern New England and the northern Mid- Atlantic
that have lowered FFG values from recent heavy rains. However,
given the low confidence in the mid to upper level trof evolution,
at this time range, only a marginal risk is depicted from central
NC, northeastward through the coastal Mid-Atlantic into southern NY
State and southern New England.

Oravec
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