FOUS30 KWBC 050806
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
406 AM EDT Wed Aug 5 2026

Day 1  Valid 12Z Wed Aug 05 2026 - 12Z Thu Aug 06 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE CENTRAL PLAINS TO MIDDLE MISSISSIPPI VALLEY AND ALONG THE SOUTH
CAROLINA COAST...

...Central Plains to Mid/Upper Mississippi Valley...
An upper level trough and associated cold front will continue its
sluggish trek through the central/north-central states.
Thunderstorms are expected to fire along/ahead of the frontal
boundary and will be steadily fueled by an influx of Gulf moisture
northward into the boundary. The latest guidance depicted a modest
southward trend with the location of the highest QPF thus the
entire Slight Risk was adjusted accordingly for an elevated threat
for excessive rainfall was maintained given some potential overlap
with rain the previous day affecting antecedent conditions.

...Southern to Central Appalachians into the Northern Mid-Atlantic...
Whatever is left of the upper level trough across the eastern U.S.
should devolve into a shear line by midweek. However, a moist and
unstable environment (PWs greater than the 75th percentile in an
already moist season of the year) will continue and expand
northwestward as the upper energy shifts. Scattered rainfall with
high rain rates can be expected thus maintaining a Marginal Risk
for excessive rainfall and local flash flooding potential.
Convection overnight along the South Carolina coast may bleed into
the initial hours of this forecast period. Charleston and the urban
corridor are very sensitive to rainfall intensities of 1-2
inches/hour, which may materialize early this morning. Therefore a
targeted Slight Risk area was raised for much of the South Carolina
Coastline and back into the Charleston metro.

Convection may once again be enhanced over portions of the Florida
Peninsula, but given a likely rainfall focus over the less
sensitive areas of the Everglades westward. There is a non zero
potential for excessive rainfall and/or very isolated flash
flooding concerns.

...Southwest/Southern High Plains...
There will be a persistent influx of moisture along the southern
periphery of the Southwest upper high, although its been noted that
there is a less focused area for where higher QPF will occur. A
Marginal Risk remains for much of Arizona and New Mexico for
isolated flooding and runoff issues.

Campbell
 

Day 2  Valid 12Z Thu Aug 06 2026 - 12Z Fri Aug 07 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE
SOUTHWEST THROUGH THE CENTRAL/SOUTHERN PLAINS, MIDWEST, AND EAST...

...Central Plains into the Lower Missouri Valley...
Organized convection is expected to fire up along the southward
moving cold front. During the overnight hours, moist, southerly
flow will be increasing over the frontal boundary which will lead
to locally heavy rainfall, potentially accumulation around 2.5 inches.

...Lower Lakes, Ohio Valley into the Northern Mid-Atlantic...
A slow-moving frontal boundary expected to persist as shortwave
energy track east along the southern edge of the Westerlies,
helping to accentuate lift in the high PW axis in the vicinity of
this front. Moderate to locally heavy rain totals expected with
hourly rain amounts up to 2.5" possible, supporting at least
isolated runoff issues in urban areas and places with some degree
of soil saturation.

...Southern to Central Appalachians...
A broad Marginal Risk covers the Central to Southern Appalachians
for widespread scattered convection. Lasted guidance continues to
have a fair amount of spread in QPF amounts and placement of the
highest accumulations. Although the details remain uncertain, PW
values are expected to remain in the 1.5-1.75"+ range so hourly
rain amounts upwards of 2.5" could lead to runoff issues,
particularly in urban areas and within sharp relief.

...Southwest/Southern High Plains...
Monsoonal convection will continue through this period thus the
Marginal Risk was maintained for much of the Southwest and Southern
Rockies. While there is continued low confidence with details,
locally heavy rains with hourly amounts up to 2" could lead to
isolated runoff issues.

Campbell
 

Day 3  Valid 12Z Fri Aug 07 2026 - 12Z Sat Aug 08 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE LOWER AND MID MISSISSIPPI VALLEY EAST AND NORTHEAST INTO THE
MID ATLANTIC AND NEW ENGLAND, ACROSS THE UPPER MISSISSIPPI VALLEY,
AND OVER THE SOUTHWEST...

...Lower Lakes, Ohio Valley into New England...
An axis of high PW values...1.50-1.75"+ expected to continue to
stretch from the Lower Mississippi Valley, northeastward into New
England in the southwest flow between the western Atlantic upper
ridge and the broad mean trof across the Great Lakes into the Ohio
Valley. Shortwave energy in this southwest flow will help
accentuate lift in this high PW axis, supporting widespread
scattered convection across these areas. There may be better
organization to the convective activity across the Lower Lakes/Ohio
Valley region in the vicinity of a slow moving frontal boundary
expected to stretch west southwest to east northeast across this
area. The risk level was maintained at marginal, but with FFG
values relatively low across the eastern Lakes/Northern Mid-
Atlantic, an upgrade is possible, especially as more hi res
guidance becomes available.

...Southern to Central Appalachians...
PW values in the 1.5 to 1.75 inches range will persist across the
region during this period aiding in the local enhancement of the
widespread scattered convection. A broad Marginal Risk covers the
Central to Southern Appalachians where localized hourly rain
amounts of 1-2"+ could lead to runoff issues, particularly in urban
areas and within areas of steep terrain.

..Southwest...
While there continues to be low confidence with QPF details,
locally heavy rains and isolated runoff issues will continue in the
axis of above average PW values expected across this area. A
Marginal Risk area remains in effect for much of Arizona and New Mexico.

Campbell/Oravec
 

Day 4 and Day 5  Valid 12Z Sat Aug 08 2026 - 12Z Mon Aug 10 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST, FROM PORTIONS OF THE NORTHERN PLAINS ACROSS THE LOWER
LAKES AND INTO THE NORTHEAST AND ACROSS THE CENTRAL TO SOUTHERN
APPALACHIANS...

For both the day 4 and 5 period, broad cyclonic flow expected to
persist across the northern tier of the CONUS from the Northern
Plains/Upper MS Valley, eastward through the Lower Lakes and into
the Northeast. A frontal boundary is the mean will persist along
the southern edge of the westerlies on the south side of this broad
trof. Embedded shortwaves in this broad cyclonic flow will
accentuate lift in the vicinity of this front this weekend where PW
values are expected to rise to 1.50-1.75" ahead of each set of
shortwave energy.

...Lower Lakes/Upper OH Valley into northern New England...
For day 4...a lead area of height falls moving along the southern
edge of the westerlies will support widespread scattered convection
from the Lower Lakes/Upper OH Valley, east northeastward into much
of NY State and northern New England. Locally heavy rains and
isolated runoff issues possible.

...Upper MS Valley into the Mid-West...
This will be followed by a second area shortwave energy pushing
east southeast from the Northern Plains into the Upper MS
Valley/Mid West region Saturday night into early Sunday. The low
level southerly to southwesterly flow is expected to strengthen
into this front, increasing PW values to 1.50-1.75"+ and supporting
heavy to locally excessive rainfall totals in what may be an area
of organized convection. The marginal risk area was drawn to
encompass the current spread in model qpf axes.

...Southern to Central Appalachians into the Southeast...
A broad marginal risk is depicted through the Central to Southern
Appalachians into the Southeast day 4 and across the Central to
Southern Appalachians day 5 for widespread scattered convection.
Not a lot of confidence in details, but with PW values expected to
remain in the 1.5-1.75"+ range, localized hourly rain amounts of
1-2"+ could lead to runoff issues, particularly in urban areas and
within areas of steep terrain.

...Northern Plains/Upper MS Valley into the Lower Lakes...
No changes to the large scale pattern for day 5, as shortwave
energy continues to push east southeastward along the southern edge
of the westerlies. The combination of the lead area of shortwave
energy that moved into the Upper MS Valley/Mid West region day 4
moving downstream into the Lower Lakes and additional upstream
shortwave energy moving from the Northern Plains into the Upper MS
Valley day 5, will support a widespread region of potentially
locally heavy rains and isolated runoff issues. Confidence is low
with qpf details, but there will be the potential for organized
convection in the vicinity of the west to east oriented front,
supporting locally heavy rains and isolated runoff issues.

..Southwest...
No significant changes to the broad marginal risk area across the
Southwest for monsoonal convection both day 4 and day 5. While
there continues to be low confidence with qpf details, locally
heavy rains and isolated runoff issues will continue in the axis of
above average PW values expected across this area.

Oravec
$$
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 * Origin: capitolcityonline.net * KY, USA (618:250/10)