AGUS74 KWCO 310119
AHDNWC

Area Hydrological Discussion #099 - EXPERIMENTAL
NWS National Water Center - Tuscaloosa, AL
813 PM CDT Fri May 30 2025

POTENTIAL IMPACTS: Flooding expected, isolated considerable urban
flooding possible
WHERE: Mid-Atlantic into southern New York
WHEN: Through tonight

FORECAST RAINFALL AND ANTECEDENT CONDITIONS... 
QPF: 1 - 2", locally higher (HRRR/HREF)
Rain Rates: 1 - 1.5"/hr (HRRR)
Soil Moisture: 55 - 65% RSM (0 - 10 cm, NASA SPoRT)
Streamflows: Normal to above normal (USGS)

DISCUSSION...
Widespread moderate with locally very heavy rain rates will bring the
potential for flooding to the region through tonight. Antecedent
conditions will initially mitigate flooding over the region, however
training of moderate precipitation will quickly overwhelm
infiltration capacity resulting in rapid runoff into streams. The
greatest concern will be flash flooding in and near poor drainage
basins, where considerable impacts would be possible if slow moving
convection moves over the basin. 

The NWM Short-Range Forecast continues to highlight the potential for
rapid-onset flooding (ROF),with widespread ROF trends greater than
25% within the area of concern and scattered areas greater than 75%
throughout. Annual-exceedance probabilities are generally near 50% or
greater, but there are some forecast flows of 10 - 2%, particularly
across the eastern WV Panhandle to near Baltimore to Philadelphia.
These low AEPs suggest the potential for isolated significant flows
on small streams. Nevertheless, given antecedent conditions, the
primary concern will be in and around urban areas. 

GRAPHICAL REPRESENTATION weather.gov/owp/operations-ahd

Additional National Water Center products are available at
weather.gov/owp/operations

//GKendrick
ATTN...WFO...BGM...ALY...OKX...CTP...LWX...PHI
ATTN...RFC...RHA...TAR...WPC