Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
903 PM EDT Wed Jul 29 2026
Day 2
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...

...2030Z Update...

No major changes were needed with this afternoon's update. The
Slight Risk over the Plains and Midwest was expanded westward with
the latest update due to guidance moving the area of heaviest
rainfall westward as compared to prior forecasts. Otherwise, few
changes were needed. The heaviest rains through the period continue
to be forecast from northeastern Nebraska through southwestern
Minnesota.

Storm coverage and intensity across the 4 Corners region appears
significantly muted as compared with previous days. The Marginal
Risk in the area was trimmed back to portions of Arizona and New
Mexico as a result.

A moisture feed from the Gulf will allow for a few storms to form
over western Arkansas and into the Lower Mississippi Valley. The
Marginal Risks were combined along the front.

Lingering moisture along the New England coast could continue to
pose an isolated flash flooding threat, so the Marginal was
maintained and expanded a bit over southeastern Massachusetts,
Rhode Island, and eastern Connecticut.

Wegman

...Previous Discussion...

...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 given the potential for training and repeat-convection. The
Slight Risk remained in good shape and only minor adjustments were
needed to covers the 29/00Z ensemble guidance and to account for
the uncertainty/spread among the models.

...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 near the state line.

...New England...
The departing low pressure is expected to be across eastern MA at
the start of the period and transition off the coast during the
period. 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.

Taylor/Bann


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt