531
AGUS74 KWCO 061527
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
915 AM CST THU MAR 6 2025

.Synopsis...
Recent rainfall and lingering snowmelt may generate flooding impacts, river
rises expected later this week across the Northeast...Isolated flash and
urban small stream flooding possible across portions of
California...Flooding and mudslides possible in Puerto Rico...Ice jam
flooding continues through the afternoon in Montana and North Dakota...

.Discussion...

.Northeast...
Recent rainfall and lingering snowmelt may generate river and small stream
flooding impacts across the region through today, particularly across
portions of upstate NY, as the combined runoff will continue to route into
nearby streams and rivers. Runoff may also lead to ponding of water in
low-lying areas. Ice jam flooding is also possible, as warmer temperatures
and runoff from rain and snowmelt encourage movement on ice covered rivers
and streams across the region. Current river forecasts continue to indicate
widespread action stage rises to isolated minor river flooding across the
region, particularly from northern PA through NY.

.California...
Moderate to locally heavy rainfall through today may elicit isolated flash
and urban flooding across portions of central and southern CA. Top soils
are average to wet depending on region (50 - 75%, 0 - 10 cm RSM, NASA
SPoRT) with streamflows running normal to much above normal. There is an
isolated potential for brief enhanced rainfall rates, which may generate
ponding/standing water in urban areas and isolated debris flows in recently
burned areas.

Looking ahead, additional rounds of rainfall are forecast to impact the
region early to mid next week. Given the extended time frame of the
forecast, as well as model inconsistencies, confidence remains low in the
exact magnitude and timing of flooding impacts next week.

.Puerto Rico...
Heavy rainfall associated with diurnal showers and storms may elicit urban
and small stream flooding through day 2 (Fri) over portions of the
north-central, southwest and interior areas of Puerto Rico. Mudslides are
possible in areas of steep terrain as soils become more saturated.

.Montana and North Dakota...
Ongoing ice jam flooding impacts along the Yellowstone River near Sidney,
MT will continue through the afternoon. As high flows move downstream, this
may cause breaking up of ice along the Yellowstone and Missouri Rivers,
west of Williston, ND, thus causing localized flooding impacts in this
region as well.

//TMK





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