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AGUS74 KWCO 181149
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
700 AM CDT TUE AUG 18 2026

.Update...

The Central Plains into the Middle Mississippi Valley was removed from this
mornings FHO, as a southward shift in the heaviest QPF has diminished the
overall flood threat. However, isolated flash flooding can`t be ruled out
if heavier rainfall develops over more vulnerable areas. The Central
Appalachians were also removed as rainfall has exited the region.
Meanwhile, adjustments continue to be made to the Limited selection across
Illinois and Indiana as rivers recede and drop below moderate flood stage.
The Limited selections for Alaska and Micronesia remain unchanged, though
timing was updated in their regional talking points.

//RMF

Previous Discussion as Follows:

...Significant river flooding continues across Illinois and Indiana...Small
stream and river flooding possible in Alaska...Flash and urban flooding
possible across the Upper Ohio Valley into the Central Applachians...Flash
flooding and mudslides possible in Micronesia

.Illinois and Indiana...
Widespread minor to moderate river flooding will continue across portions
of Illinois and much of Indiana through the week as runoff from recent
significant rainfall continues to route downstream. Additional showers and
storms are expected to move across this region Tuesday and Wednesday,
although the heaviest rainfall is currently forecast south of the areas of
ongoing river flooding, thus limiting some of the potential for new and
renewed flooding. However, given the hydrologic sensitivity of the region,
isolated flash and urban flooding impacts remain possible.

.Alaska...
Periods of heavy rainfall through Wednesday will likely generate small
stream and river flooding across the Susitna Valley, with the heaviest
rainfall expected across the headwaters of the Yentna River. Given
saturated antecedent conditions from recent rainfall events, a limited
impact area was added for the afternoon issuance of the FHO and this region
will be monitored for any potential upgrades over the next couple of days.

.Upper Ohio Valley into the Central Appalachians...
Clusters of storms will continue to progress across portions of
southeastern Ohio, and much of West Virginia through tonight, likely
generating flash and urban flooding impacts, as well as rapid small stream
rises across the region. Recent rainfall has left this region
hydrologically vulnerable, and while areal rainfall totals are not
particularly high, any additional rainfall will quickly produce runoff into
already elevated streams and urban drainages, increasing the potential for
flash and small stream flooding concerns. Guidance from both the NWM High
Flow Magnitude Forecast, as well as the 18-HR Unit Discharge, are
suggesting the potential for locally significant responses, particularly
along the Ohio/West Virginia border and across much of central West
Virginia. Impacts will be greatest across steep terrain and urban areas,
especially if more slow-moving storms or more robust rainfall rates
materialize.

.Central Plains into the Middle Mississippi Valley
Rainfall returns to portions of eastern Nebraska, much of Iowa, and
northern Missouri on Tuesday where the soils remain saturated from recent
rainfall. The GFS and NBM-forced NWM continue to signal isolated responses
across this region. Confidence in magnitude and overall coverage of
hydrologic responses is uncertain given the convective nature of the event
however, isolated flash and urban flooding remains possible.

.Micronesia...
Flash flooding and mudslides remain a threat over the next several days due
to heavy tropical rainfall from Invest 92W.

//JDP

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



$$