Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
844 PM EDT Fri Jul 17 2026
Day 3
Valid 12Z Sun Jul 19 2026 - 12Z Mon Jul 20 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE WESTERN U.S., SOUTHEAST, AND LOWER MID ATLANTIC...

2000 UTC Update: Minor changes were made to the Day 3 ERO, based on
the latest (12Z) guidance suite. Per collaboration with WFO RAH,
felt that an expansion of the Marginal Risk area into central NC
and northeast SC was warranted. Have also expanded the Marginal
along the eastern Gulf Coast, while again nudging the western
periphery of the Marginal Risk to include more of southern NV
(including Las Vegas) and portions of southeast CA.

Not much change in the overall monsoonal pattern, though most of
the global guidance is a bit more diffuse with the heavier QPF
totals. Still think a Slight Risk will be likely somewhere,
probably very similar to the Slight Risk area on the current Day 2
ERO, but for now given the variance in the model QPFs, will keep
the Marginal Risk going and reassess with the next 1-2 forecast
cycles.

Hurley

Previous discussion...

...Western U.S....
The monsoon pattern will persist across the Western CONUS,
maintaining at least scattered convection from the West Texas, New
Mexico and Arizona into the Great Basin and Rockies. PW anomalies
of 2-3+ standard deviations will continue to center over portions
of the Great Basin. The higher areal average precipitation amounts
are expected to once again align along the Mogollon Rim into
southern Utah. Given the prior rainfall and moist soil conditions,
these areas will remain vulnerable to rapid runoff, with the
area's complex terrain and slot canyons raising localized concerns.
A broad Marginal Risk was maintained to highlight the daily
convective potential and runoff concerns.

...Florida Gulf Coast...
Deep tropical moisture and a slow-moving mid-to-upper level low
over the eastern Gulf will maintain a heavy rainfall threat.
Favorable low-level convergence along the eastern flank of the
system may produce heavy rainfall along Florida's West Coast. Some
models show the system lifting out to the north this period,
bringing the threat for heavy rain into the Big Bend region. A
Marginal Risk was maintained from the Tampa Bay area to the Big
Bend to highlight the potential for heavy rain along this area.

...Virginia Tidewater and Eastern North Carolina....
A cold front dropping out of the north is expected to slow across
this region, maintaining a deep moisture pool in advance. Pre-
frontal convergence and diurnal heating will likely produce pockets
of heavy, slow-moving thunderstorms prior to its passage. With
some differences in the details, model consensus continues to
indicate that 1-2 inch, with locally heavier amounts, are likely
within the Marginal Risk area, producing at least isolated concerns.
A targeted upgrade to a Slight may be required, especially if the
model consensus for heavy amounts begins to center across the more
vulnerable Tidewater region.

Pereira

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt