Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Sun Aug 30 2026
Day 2
Valid 12Z Mon Aug 31 2026 - 12Z Tue Sep 01 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE INTERMOUNTAIN WEST...

...Intermountain West...

A broad Slight Risk for excessive rainfall and elevated threat for
flash flooding remains in effect from Arizona northward to Utah
and Colorado. During this period a series of upper level
disturbances will be traveling through the deep longwave trough
over the Pacific Northwest. Meanwhile Pacific moisture will be
pooled over the region along a steady influx leading to anomalous
moisture of 2-3 sigma above normal. This environment will be
supportive of scattered showers and thunderstorms developing with
the monsoon. Much of this area is very prone to flash flooding
should heavy enough rains occur, which is likely given the history
of afternoon showers and storms in this same region under the same
pattern. The degree of moisture expected could lead to hourly rain
amounts to 2" wherever cells sit, merge, or train especially near
favored terrain, urbanized areas, box/slot canyons, arroyos/dry
washes, and burn scars being the most prone to flooding.

...Upper Midwest/Lower Great Lakes/Northeast...

Organized showers and thunderstorms expected thanks to upper-level
forcing for ascent supporting local enhancement. PW values above
the 90th climatological percentile will revolve around the northern
flank of the ridge and reach the Northeast by evening. The
environment will be supportive for at least localized areas of
excessive rainfall across much of New York, northern Pennsylvania,
and as far east as the I-95 corridor from northern New Jersey to
southern New England. A Marginal Risk remains in effect from the
Minnesota Arrowhead to portions of the Northeast.

...Eastern Gulf Coast...

The Marginal Risk for excessive rainfall remains in effect. Shortwave
energy moving westward underneath the closed 500 mb High will be
the focus for potentially more numerous (organized) convective
clusters during peak diurnal heating, especially when interacting
with the Atlantic and Gulf sea breezes.

Campbell/Mullinax/Wegman


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