020
AGUS74 KWCO 311502
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT THU JUL 31 2025

.Synopsis...
Considerable flash and urban flooding in the Mid-Atlantic into the
Northeast...Isolated flash flooding may occur in portions of the Northern
Rockies ...Isolated flash and arroyo flooding continues for New
Mexico...Isolated flash, urban and small stream flooding possible in Puerto
Rico...Ongoing and forecast river flooding continues in Iowa...

.Mid-Atlantic into the Northeast...
Heavy rainfall today is expected to result in considerable flash and urban
flooding impacts across the Mid-Atlantic and Northeast, primarily along the
I-95 urban corridor. Elsewhere, isolated flash, urban, and small stream
flooding is anticipated. Rainfall rates may exceed 2 inches per hour within
the area of concern with training of thunderstorms also possible. While
antecedent conditions are generally dry to normal (55-75%, 0-10 cm RSM NASA
SPoRT) and associated streamflows are similarly dry to normal (USGS), the
forecast high rainfall rates could locally overwhelm existing infiltration
capacity, leading to excess runoff. Although river flooding is not
expected, rapid rises on area streams and rivers are likely.

The National Water Model (NWM) Short-Range Forecast (SRF) indicates
rapid-onset flooding (ROF) across the region, with the highest consistency
observed in areas extending from Washington, D.C. to the New York City
metropolitan area. Peak flow arrival times on streams and rivers are
forecast to occur 14 to 18 hours and beyond in these areas. Given these
indicators and the high rainfall rates, significant flooding is a distinct
possibility, particularly in urban areas.

.Northern Rockies...
The potential for flash flooding due to heavy rainfall exists through this
evening, particularly near burn scars, low-lying areas, and small streams.

.New Mexico...
Isolated flash and arroyo flooding is possible in parts of New Mexico as
monsoonal moisture persists through this evening. High rainfall rates and
training thunderstorms over recent burn scars, urban areas, and poorly
drained regions may pose a significant risk of flooding impacts.

.Puerto Rico...
Tropical moisture is expected to bring the potential for isolated flash,
urban, and small stream flooding to the island through early next week.
Consecutive days of rainfall may lead to ponding in low-lying and poorly
drained areas.

.Iowa...
Minor and moderate, with isolated major, river flooding is currently
ongoing and is forecast to continue into the weekend. No additional
rainfall concerns for renewed flooding are anticipated over the next 7 days.

//TMK





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