214
AGUS74 KWCO 261513
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT THU JUN 26 2025

.Synopsis...
Flash and river flooding expected across the Central Plains and Mid to
Upper Mississippi Valley...Flash flooding possible today across New Mexico
and West Texas and tomorrow across Upstate New York to Northern New
England...Flooding possible through the weekend across the Mariana Islands
and American Samoa...

.Central Plains and Mid to Upper Mississippi Valley...
Additional periods of convective rainfall through day 2 (Fri) will likely
generate new and renewed flooding impacts across the region, with locally
significant flooding possible. Generally 2 - 6" of rainfall (locally
exceeding 7" MRMS QPE) over the past 72 hours has saturated soils (RSM
70%, 0 - 10 cm NASA SPoRT), especially across much of NE, IA, MN, and WI,
and additional rainfall today and tonight will eliminate any remaining
infiltration capacity. Scattered minor to moderate river flooding is
ongoing and forecast across the region as a result of heavy rainfall this
week. As such, robust rainfall rates from convection today will eliminate
any remaining infiltration capacity across these regions, immediately
running off into already flooded rivers and streams and overflowing urban
drainages. Guidance from all of the deterministic forcings of the National
Water Model (HRRR, GFS, and NBM) continues to depict robust streamflow
responses across NE, IA, MN, and WI, with the majority of the peak flows
occurring within the next 24 - 48 hours. Similar to recent days,
significant AEPs (below 10%) are noted across southeastern NE,
northern/central IA, southern MN, and western WI and given already
sensitive antecedent conditions in place, locally significant flooding
impacts are possible. Additional showers and storms are possible again on
days 3 - 4 (Sat - Sun) although confidence is low in the placement and
magnitude of hydrologic responses at this time.

.New Mexico and West Texas...
The threat for localized flash flooding will continue across portions of
southern NM and far-west TX through day 2 (Fri) as monsoonal showers and
storms slowly move across the region. Coverage and intensity of rainfall
will be less than earlier in the week however, heavy rainfall over the
last several days has wetted soils across the region, keeping this area
vulnerable to additional flooding impacts. Flooding of low-water crossings,
arroyos, and rapid rises in areas of steep or complex terrain is possible.
Flash flooding and debris flows remain possible near recently burned areas.
The HRRR-forced NWM is indicating isolated small stream responses across
eastern NM this afternoon and evening. Corresponding AEPs indicate that
most stream rises should remain within the channel (near 50% AEP) however,
there are isolated AEPs below 10%, supporting the potential for rapid
stream rises and flooding impacts outside of recently burned areas.

.Upstate New York to Northern New England...
Flash flooding is possible on day 2 (Fri) into early day 3 (Sat) across the
northern portions of NY, VT, NH, and northwestern ME due to heavy rainfall.
Rainfall totals of 2"+ are expected from this event, and with topsoils near
normal and streams running generally below normal, the small stream and
river flooding threat should be minimal. Localized flash flooding is the
primary concern due to the complex terrain of the area and potentially high
rainfall rates.

.American Samoa...
Heavy rainfall across the region may generate flash and urban flooding
impacts through day 2 (Fri). Landslides are also possible in areas of steep
terrain.

.Mariana Islands...
Heavy rainfall (5 - 10") associated from monsoonal flow may generate flash
flooding across the islands through the weekend.

//JDP





$$