Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
423 AM EDT Mon Jul 6 2026
Day 2
Valid 12Z Tue Jul 07 2026 - 12Z Wed Jul 08 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE NORTHERN PLAINS...

...Northern Plains...

During this period a shortwave rounding the ridge anchored over the
Four Corners will make its way through central Montana to western
Minnesota. This shortwave will drive downstream PVA and height
falls while concurrent but modest RRQ diffluence in the tail of a
distant jet streak helps enhance synoptic lift. At the surface, a
wavering boundary with a wave of low pressure moving along it will
try to shift north in response to subtly increasing southerly low-
level flow, with the resulting isentropic ascent aiding lift across
the region. This robust ascent will act upon PWs that will surge
to 1.25 to 1.75 inches, or around +2 sigma, collocated with a plume
of MUCAPE exceeding 2000 J/kg.

Areal coverage of convection will increase through the day,
tracking from west to east. The environment will be favorable for
backbuilding or training. Hourly rainfall as much as 0.75"-1.0"+
is likely, which could create locally 2-3" of rainfall as reflected
by modest (5-15% chance) of 3"/24 hrs. Soils across this part of
the country have been recently wet thus increasing sensitivity. A
Slight Risk remains in effect from the eastern Dakotas to western
Wisconsin. A broad Marginal Risk extends from eastern Montana to
north-central Wisconsin.

...Mid-Atlantic States...

Much of this region will continue to have scattered to widespread
thunderstorms as weak impulses traverse through the trough
overhead. In general, these storms should be of the pulse variety
and move E/NE on 15 kts of 0-6km mean wind. However, the impressive
thermodynamics in place (PWs over 1.75 inches overlapping MUCAPE
of 1000-2000 J/kg) will support rainfall rates of 1-2"/hr, through
which any short-term training or repeating rounds could lead to
instances of flash flooding.

...Eastern Massachusetts & Rhode Island...

A wave of low pressure will be tracking south of Rhode Island
during this period keeping some showers and thunderstorms in place
across southern New England. Although new accumulations are
expected to be modest hourly rates of 1+ inches/hr will be
possible. A Marginal Risk area was maintained for this period.

Weiss/Campbell


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