141
AGUS74 KWCO 161510
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT FRI MAY 16 2025

.Synopsis...
Potential for isolated flash flooding today in the Northeast... Multiple
days of rainfall, potential for flash and river flooding across the Ohio
River Valley and portions of the Middle Mississippi Valley and the Central
Plains... Flash flooding threat continues for Puerto Rico and the USVI...
Potential for ice jam flooding in portions of Alaska...

.Northeast...
Isolated flash flooding is possible today, primarily in the steep and
complex terrain of PA, upstate NY, and New England, due to intense rainfall
rates and training convection. The National Water Model (NWM) Short Range
Forecast (SRF) is indicating potential for rapid onset flooding in portions
of central and eastern PA as convection moves through the area this
morning, and more isolated signals are present in portions of northern NH
and western ME.

.Ohio River Valley...
Isolated flash flooding is possible across KY and WV today as training
convection crosses the states. With wet but not fully saturated top layer
soils (NASA SPoRT), intense rainfall rates and training will be the primary
driver of any flash flooding that occurs. The NWM SRF indicates
probabilities of rapid onset flooding above 50% across much of southern KY
over the next 12 hours, supporting the potential for flooding.

Rainfall returns to the region on days 4 - 6 (Mon - Wed), bringing a
renewed threat for flooding impacts. Daily rainfall amounts are generally
expected to remain below 2" and at this time, the placement of the highest
daily amounts do not overlap. The placement of the highest daily amounts
will likely shift as we approach this time period, and with convection
expected, intense rainfall rates and training will again be the primary
cause of any flash flooding that occurs. As such, confidence in the exact
placement of any flash flooding impacts remains uncertain. In addition, the
latest river ensemble forecasts (HEFS, MMEFS) are in disagreement on the
degree of river flooding expected. While the HEFS is only indicating
potential for minor river flooding in the White (IN) and Wabash (IL/IN)
river basins over the next 10 days (30% chance of exceedance), the
GEFS-forced MMEFS is indicating potential for moderate flooding in those
basins with more widespread minor river flooding throughout the OH Valley.
Overall, confidence remains low in widespread and significant flooding
impacts, but this region will be monitored closely in the coming days.

.Middle Mississippi Valley and the Central Plains...
Isolated flooding impacts and minor river flooding are possible across
these regions through day 7 (Wed), primarily across MO and IL, due to
multiple rounds of rainfall totaling 2 - 5", with locally higher amounts
possible. Flash flooding due to intense rainfall rates appears to be the
primary threat, with the best chances in eastern portions of KS and NE and
much of MO and northern AR on day 3 (Sun). The rainfall is forecast to
shift eastward on days 4 and 5 (Mon and Tue), primarily into MO, southern
IA, and IL, bringing the threat of flash flooding to those areas. River
ensemble forecasts (HEFS) indicate some potential for minor river flooding
(30% chance of exceedance), primarily in the Lower Missouri River Valley in
MO. Overall, confidence remains low in widespread and significant flooding
impacts, but this region will be monitored closely in the coming days.

.Puerto Rico and the USVI...
Isolated flash flooding is possible across all of the islands today, but
the greatest flooding threat over days 2 and 3 (Sat and Sun) is expected to
be confined to Puerto Rico. With saturated soils in place and rivers
running above normal, any additional rainfall will quickly become runoff
and could lead to locally significant flash and river flooding.
Mudslides/landslides are also possible across central and eastern Puerto
Rico.

.Alaska...
In the northern Seward Peninsula, the Buckland River could rise out of its
banks sometime over the next several days due to ice jamming. This could
lead to minor flooding impacts in the town of Buckland.

//Watson

$$