FOUS30 KWBC 020829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Sun Aug 2 2026

Day 1  Valid 01Z Sun Aug 02 2026 - 12Z Sun Aug 02 2026

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE FLORIDA BIG
BEND REGION, COASTAL NORTH CAROLINA AND THE EASTERN GREAT LAKES
INTO THE NORTHEAST AND NORTHERN/CENTRAL APPALACHIANS...

...East Coast States...

Widespread showers and thunderstorms are expected from the Gulf
Coast of Florida through the Mid-Atlantic States, and into the
interior Northeast. A highly amplified trough will be tracking
though the region. A strong upper level jet will help provide
impressive synoptic ascent from the Gulf Coast all the way into New
England. Meanwhile Gulf moisture will be drawn northward ahead of
the system with PW values climbing into the 2-2.25 inches range.
Widespread thunderstorm are expected to break out and capable to
produce rain rates of 1-2 inches/hour with the potential for
repeating/training of cells. A broad Marginal Risk are spans from
the eastern Gulf Coast up the Eastern Seaboard to th Northeast and
Ohio Valley.

There are three areas with a more focused threat. The first is
across the Florida Gulf Coast/Big Bend and just inland where heavy
rain will occur over recently saturated soils. An additional 3-5
inches of rain is possible (30-50% chance of at least 5 inches)
due to backbuilding of cells across the Gulf repeating onshore with
2-3 inches/hour rates. Within this region, an enhanced slight risk
was added for Taylor, Dixie, and Lafayette counties which is where
the 2-day rainfall is expected to be heaviest.

Another area of locally higher excessive rainfall risk exists along
the eastern Great Lakes from around Cleveland, Ohio through
Buffalo, New York and into the Northern Adirondacks and southward
for the Central Appalachians where there is a Slight Risk for
excessive rainfall. While instability may be a bit less here, this
is also the region where a pivoting deformation axis and
accompanying mid- level TROWAL may exist north of the closed low.
This will produce some higher thermodynamics into which storms,
which will be slow moving and training, can repeat with 1-2
inches/hour rain rates.

And the third area is for coastal North Carolina where there is a
signal for 2-5 inches of rainfall too fall over recently saturated
soils. A Slight Risk area was raised for this part of the state.

..Southwest...

During this time the ridge will be expanding eastward however the
convective activity is expected to stay suppressed across Arizona,
New Mexico and West Texas. The challenge Sunday is that it appears
there will be some drying that occurs from NE to SW as a decaying
front drops across Texas, followed by a weak surface trough as
well. This suggests that during peak heating, there will actually
be somewhat of a deterioration of the environment, further limiting
convective coverage. Any storms that do develop will have the
potential to yield local hourly rates of 1 inch/hour that lead to
isolated instances of flash flooding.

Campbell/Weiss
 

Day 2  Valid 12Z Sun Aug 02 2026 - 12Z Mon Aug 03 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE TRI-STATE
AREA OF NEW YORK, NEW JERSEY, AND CONNECTICUT, COASTAL CAROLINAS
AND BIG BEND OF FLORIDA...

...East Coast...

The impressive upper trough/low moving across the Ohio Valley is
progged to cutoff once again as it digs into the Southeast by
Tuesday morning. Downstream of this anomalous feature, robust PWs
of more than +2 sigma will flood the Atlantic Seaboard, combining
with a ribbon of elevated instability within the deep layer WAA to
produce an environment supportive of heavy rainfall for nearly the
entire coast. While specific locations for heavier rainfall and a
greater excessive rainfall risk are difficult to discern at this
time range, it appears nearly any location that received repeating
showers and thunderstorms with 1-2 inches/hour rain rates could
experienced impacts. The Marginal Risk area stretching from Florida
to Maine was maintained.

The narrow Slight risk for the Tri-State area of CT/NJ/NY and
northwest Rhode Island was maintained due to extremely vulnerable
soils from recent heavy rainfall in this area. A small Slight
Risk area was raised for the Big Bend of Florida where additional
heavy rain may pivot onshore Monday after 2-days of heavy rain this
weekend. A Slight Risk was also raised for coastal areas of South
and North Carolina given additional rainfall is expected to fall
over very saturated soils.

...Southwest...

The ridge will continue to expand farther east while weak
vorticity impulses rotate around it. Moisture and instability will
gradually lift northward during this time, allowing for an
expansion north of an environment supportive of heavy rain. The
limiting factor Monday appears to be instability. The Marginal Risk
area was maintained for isolated instances of excessive rainfall
leading to flash flood related impacts are expected for parts of
Arizona, New Mexico and far western Texas.

...Northern Plains...

A shortwave will quickly track along the International border
bringing height falls to the Dakotas and Minnesota. Southwest flow
will direct Gulf moisture and instability northward to help support
the development of heavy rainfall. Storm motion is expected to be
quite progressive however there may be briefs periods where
training/backbuilding occurs. As rainfall rates climb to 1+
inches/hour, any training could create locally excessive rainfall.

Campbell/Weiss
$$
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