Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1159 AM EDT Fri Jul 17 2026
Day 2
Valid 12Z Sat Jul 18 2026 - 12Z Sun Jul 19 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM WEST TEXAS AND
SOUTHERN NEW MEXICO TO SOUTHERN UTAH, AND FROM THE NORTHERN MID-
ATLANTIC INTO SOUTHERN NEW YORK AND NEW ENGLAND...

...Western U.S.....
An expansive monsoonal convective pattern remains locked in place
across the Western CONUS, supporting the continuation of a broad
Slight Risk extending from West Texas and southern New Mexico
northwestward across central and northern Arizona into southern
Utah. An increase in low level moisture transport into the region,
coupled with the moisture already in place will support PW
anomalies 1.5-3 std dev above normal across much of this region.
This moisture will likely once again support widespread convective
development across the area.  With ample daytime heating and
sufficient instability, these storms will be capable of producing
efficient rainfall rates. Given the history of recent
precipitation, soils have become increasingly sensitive across
portions of the region, elevating the potential for rapid runoff
and flash flooding concerns.

...Ohio Valley/Appalachians to the Mid Atlantic and Northeast...
A progressive cold front dropping southeastward will interact with
an anomalously moist airmass pooling ahead of it. Atmospheric
profiles will be highly favorable for efficient warm-rain
processes, featuring PWs over 2 inches and deep warm-cloud layers.
Where daytime heating and mid-70s dewpoints break capping
inversions, prefrontal convection will tap into greater instability
and raise rainfall rates.

This environment along with the concentration of urbanized areas
susceptible to fast runoff provided enough confidence to extend
the Slight Risk farther east from parts of eastern Pennsylvania and
northern New Jersey across southern New York and New England.
Limiting factors to highlighting a more widespread flash flooding
threat include fast storm moisture and lingering model discrepancy
regarding the exact placement of the heaviest precipitation axes.

Farther west through the central Appalachians into the Ohio Valley,
a broader Marginal Risk remains in place to cover what is
anticipated to be more isolated concerns.

Pereira


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