Hydrometeorological Discussion
Issued by NWS Tuscaloosa, AL

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142
AGUS74 KWCO 181457
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
957 AM CDT SAT OCT 18 2025

.Synopsis...
Widespread rainfall and isolated flooding potential across the Middle
Mississippi Valley into the Great Lakes...Isolated flash flood potential
across American Samoa through this weekend... A series of atmospheric
rivers expected late week for the Pacific Northwest... Daily afternoon
isolated flooding potential for Puerto Rico...

.Middle Mississippi Valley into the Great Lakes...
Showers and thunderstorms are expected across the entire region through
tonight, with potential for heavier rainfall totals across southern
MO/northern Ozarks, which will bring an isolated threat for flash flooding.
The soils across the entire region remain dry and as such much of this
rainfall is likely to be beneficial. However, pockets of intense or
training rainfall can overwhelm dry soils, and therefore, lead to enhanced
overland flow and flash flooding potential, especially across the complex
terrain of the northern Ozarks. Regardless, the concern for widespread
flooding concerns remains low due to the progressive nature of the system.
The National Water Model is showing isolated potential for rapid river
rises across south-central MO for this afternoon, but widespread riverine
responses are not expected, and flooding should remain localized.

.American Samoa...
An active trough is forecast to bring heavy rainfall to all the islands
through the weekend which may cause instances of flash flooding and
landslides.

.Pacific Northwest...
A series of atmospheric rivers is forecast late in the period which may
bring isolated urban and small stream flooding beginning late next week.
Rainfall through mid week looks to be beneficial to the region as soils are
dry and streamflows are low which is to be expected at the beginning of the
wet season, however numerous periods of repeated rounds of rainfall late
week through next weekend could begin to become concerning, as cumulative
totals begin approaching 7 - 10"+ across far northwest OR and western WA
along and west of the Cascades, including basins draining the Olympics.
While the extended range typically is associated with reduced confidence in
the forecast, much of the model guidance has been showing consistency in
some appreciable rainfall possible along with ensemble river guidance
(HEFS) beginning to pick up increasing chances of potential river flooding,
particularly in basins draining the western slopes of the Cascades in WA.

.Puerto Rico...
Afternoon showers and thunderstorms will continue across the island through
the weekend into early next week which may bring isolated flooding to the
island. While there is a low chance of flash flooding, some isolated areas
of urban and small stream flooding are possible.

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

This product will begin to be issued twice daily, with new issuance times,
beginning approximately 3 November 2025. The routine primary issuance time
of the product will be at 20 UTC, with routine daily updates to the
discussion being completed around 7 AM Central Time.

//JEC

$$