355
AGUS74 KWCO 201957
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
300 PM CDT MON JUL 20 2026

Increasing threat of flash flooding along the Gulf Coast this week...Flash
and urban flooding impacts are possible across the Desert Southwest and
Nevada through mid week...Flash, urban, and small stream flooding possible
over the Ohio Valley and Mid Atlantic Tuesday and Wednesday...Flooding
impacts possible in the Carolinas and southern Virginia from multiple
rounds of heavy rainfall through the week...Moderate to major river
flooding will continue across portions of Texas through the
week...Atmospheric river impacts portions of Alaska through Tuesday...

.Gulf Coast...
Tropical Depression Two continues to exhibit a flash flood threat along the
Gulf coast through the week. Current forecasts suggest that the heaviest
precipitation is likely to occur from offshore bands concentrated primarily
along the I-10 corridor from the Florida Panhandle into the east Texas
coast. Top soils and streamflows are generally near normal across much of
this area, which would initially help to mitigate widespread flooding. The
initial concerns for this event are likely flash and urban flood impacts
wherever repeated rounds of rainfall materialize. The storm is currently
forecast to proceed westward along the Gulf Coast and potentially reach
Texas by Saturday. There remains uncertainty in the final track of this
storm however, it will need to be closely watched for changes in the
placement and magnitude of potential flooding impacts.

.Desert Southwest...
The threat of isolated flash and urban flooding continues today, and
tomorrow across parts of Arizona, New Mexico, and the central Great Basin
of Utah/Nevada. The heaviest rainfall is expected across the Mogollon Rim,
and consequently the National Water Model (NWM) Short Range Forecast (SRF)
continues to show isolated streamflow responses across the complex terrain
north and east of Phoenix. Signals are somewhat muted compared to how they
looked over the weekend, suggesting impacts may be more isolated than the
last several days. Nonetheless flash and urban flooding remain possible
anywhere heavy rainfall sets up.

.Carolinas and southern Virginia...
Antecedent conditions remain relatively dry heading into this week, even
with isolated rainfall totals of 1 - 4" in the last 24 hours, but rainfall
this afternoon and repeated round Wednesday through Friday will begin to
overwhelm the dry conditions and allow for the formation of efficient
runoff processes. The NBM-forced NWM is beginning to show responses in
eastern North Carolina in responses to this rainfall, with isolated reaches
exceeding the 50 - 10% AEP thresholds. The area will continue to be
monitored as the week progresses.

.Ohio Valley into the Mid Atlantic...
Flash, urban, and small stream flooding is possible across the region
Tuesday into Wednesday. Antecedent conditions leading into this event are a
tale of two areas the first being the Ohio Valley into the Blue Ridge
mountains where topsoils and streamflows are generally near above normal
and the second being east of the Appalachians across the Piedmont/Coastal
Plains of the Mid-Atlantic where topsoils are still generally below normal
and streams flows are running at normal to much below normal. Of course the
major metropolitan areas are all found at or along the coast, making urban
flooding the primary threat here. The GFS-forced version of the NWM is
signalling potential for significant flows on small streams, with pockets
of 50 - 10% annual exceedance probabilities in the Ohio Valley and New
Jersey into New York/Connecticut.

Nevada
Isolated flash and urban flooding is possible across parts of northern and
central Nevada into California through Tuesday. Areas of steep terrain and
anywhere that received rainfall this past week will be at an increased risk
of flash flooding.

.Texas...
Moderate to major river flooding is observed or forecast across
southcentral TX following recent heavy rainfall. The only river currently
in major flood status is the Nueces, with the Frio expected to reach the
major flood threshold around mid-day on Monday. Very minimal, if any,
rainfall is expected over the next 7 days which should allow recessions to
continue unimpeded.

.Alaska...
Small stream and minor to moderate river flooding is possible along the
Kenai Peninsula and into the Anchorage area through Tuesday as an
atmospheric river impacts the region.

//Bliss

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



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