Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 PM EDT Sun Jul 19 2026
Day 2
Valid 12Z Mon Jul 20 2026 - 12Z Tue Jul 21 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE DESERT SOUTHWEST AND NORTH CAROLINA...

...Southwest and Great Basin...

Mid-level energy moving west of the region, and dry air advection
from the south will begin to diminish the heavy rainfall and flash
flooding threat over West Texas. However farther west, the
monsoonal moisture plume will remain firmly in place, ensuring
another day of efficient rainfall production over portions of the
Southwest and Great Basin. Models show the upper high originally
centered over Utah and Colorado beginning to slide southeast,
allowing moisture and energy to spread northwest into the Great
Basin and along the western slopes of the Sierra Nevada, raising
the potential for increasing storm activity and isolated runoff
concerns in those areas.

The greater heavy rainfall and flash flooding threat will remain
focused from southwestern New Mexico and southeastern Arizona
northwestward along the Mogollon Rim into northwestern Arizona.
This is expected to be the focus for better synoptic forcing and
greater instability, supporting intense short-duration rain rates
that will elevate the risk for flash flooding, especially in areas
of complex terrain, dry washes, and burn scars. For the 19Z Update,
a minor westward extension of the Slight Risk was made across
northwestern Arizona to the Lake Mead area.

...Upper Great Lakes...

An amplifying upper trough supported by energy diving out of
Canada will advance from the upper Mississippi Valley to the upper
Great Lakes. Strong southwesterly to west-southwesterly low level
inflow will continue to sustain deep moisture ahead of the cold
front and across the advancing warm front. This moisture along with
strong forcing, produced in part by left-exit region upper jet
dynamics, will generate organized convection capable of producing
rainfall rates of 1-2 in/hr. Fast storm motions should limit the
overall heavy accumulation and flash flooding threat. However,
localized short-term training could raise at least some isolated
concerns. No changes were needed here for the updated Day 2
outlook.

...North Carolina and Southern Virginia...

A lingering boundary and corresponding pool of deep moisture
convergence, with PWs generally near or slightly above 2 inches,
will support additional thunderstorms capable of producing heavy
downpours. There has been a trend for heavier QPF in today's
guidance across much of central and eastern North Carolina, and
after consultation with the local WFOs, a Slight Risk area has been
introduced for this area. Heavy rainfall expected through Sunday
night will lead to reduced FFGs and more saturated soils that will
be more prone to flooding issues.

...Gulf Coast...

The models continue to show the footprint of the heaviest amounts
associated with Tropical Depression Two over the northern Gulf
remaining mostly offshore. The Marginal Risk has been maintained along
the coast from West Florida near Tampa, to southeastern Louisiana,
which encompasses areas generally along the Interstate 10 corridor,
with the highest totals likely near the Big Bend of Florida. Moisture
pooling along an axis of enhanced low level convergence northwest
of the circulation may extend the threat for heavy rainfall further
inland into the far lower Mississippi Valley. If there are
northward trends in later model cycles, it is possible that a
Slight Risk could eventually be needed for portions of this outlook
area.

Pereira/Hamrick


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