422
AGUS74 KWCO 231516
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT MON JUN 23 2025

.Synopsis...
Locally considerable flooding expected, locally catastrophic flooding
possible through Tuesday in portions of New Mexico and Southwest Texas...
Locally considerable flash flooding, river flooding possible through mid
week in the Central Plains and Mid to Upper Mississippi Valley... Snowmelt
runoff continues to cause flooding concerns in portions of Alaska... Flash
flooding possible later this week across the Mariana Islands...

.New Mexico and Southwest Texas...
Locally considerable flooding is expected across portions of NM today
through day 2 (Tue), primarily near recently burned areas. The highest
rainfall amounts today are expected across the southeastern quarter of NM
(1 - 2"), but day 2 (Tue) could bring even greater amounts (2 - 4") across
portions of south central and north central NM. Locally higher amounts are
possible in these areas due to the convective nature of the rainfall. Low
water crossings, arroyos, and areas of steep or complex terrain will also
be particularly vulnerable to locally considerable flooding, but the
primary concern remains the potential for locally considerable to locally
catastrophic impacts near recently burned areas.

Beyond those areas under the highest threat, flash and urban flooding is
possible across much of southwest TX and surrounding areas of NM today
through day 3 (Wed) due to multiple rounds of rainfall. The National Water
Model (NWM) Medium Range Forecast (MRF) (NBM and GFS forced) continues to
signal the potential for high water conditions in portions of the Middle
Rio Grande Valley as well as streams draining the Sangre de Cristo
mountains. Associated MRF annual exceedance probabilities are below 10% for
some reaches, suggesting the potential for locally considerable flows in
normally low flow channels.

.Central Plains and Mid to Upper Mississippi Valley...
Multiple rounds of convective rainfall will bring the potential for locally
considerable flash flooding and river flooding to eastern NE, eastern SD,
IA, southern MN, and WI beginning today and persisting through day 4 (Thu).
The forecast has changed little in the leadup to this event, with
widespread totals of 3 - 5" expected and locally higher amounts possible.
Ahead of this event, topsoils are generally drier in NE and SD compared to
those in MN, IA, and WI (NASA SPoRT). Additionally, rivers in southern MN
and IA remain above the action threshold leading into this event, along
with above to much above normal streamflows (USGS). Based on these
antecedent conditions, MN, IA, and WI appear to generally be more
susceptible to flooding impacts from this event. The NWM MRF supports that
susceptibility, as both GFS and NBM-forced versions indicate the potential
for rapid onset flooding across IA, southern MN, and WI, and even further
west into eastern NE. Areas that receive multiple rounds of precipitation
will be most vulnerable, making IA and southern MN the best candidates for
potential flooding impacts. River ensemble forecasts (HEFS) also indicate
potential for minor to moderate river flooding across much of IA and
southern MN at the 30% chance of exceedance.

.Alaska...
Snowmelt continues to lead to high water levels and minor flooding on
various rivers across the state, and this will remain the case as long as
temperatures remain warm. The Chilkat River near Klukwan remains in minor
flood stage and is expected to remain above flood stage through day 2
(Tue). High water levels continue along the Yentna and Skwentna rivers in
the Western Alaska Range and the Matanuska River near Butte. Minor flooding
impacts remain possible along these rivers.

.Mariana Islands...
Heavy rainfall (5 - 10") beginning as early as late on day 4 (Thu) and
continuing through day 7 (Sun) from a tropical disturbance could produce
flash flooding across the islands.

//Watson

$$