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Hydrologic Outlook
National Weather Service Grand Junction CO
856 PM MDT Sun Sep 27 2026

Strong southwesterly winds ahead of a closed low centered over
California will pull tropical moisture from Tropical Storm Odalys and
Hurricane Polo towards eastern Utah and western Colorado, with
atmospheric moisture peaking in our area on Monday. The northerly
extent of the expected excessive rainfall poses a threat to our
southern San Juan river basins. Current forecasts suggest 1 to 4
inches of rain Monday morning through early Wednesday. At face value,
rivers and tributaries will see a rise due to the forecast rainfall.
However, localized heavier amounts could result in flooding across
the southern San Juan foothills and communities further downstream.

Rivers have responded rapidly to recent rainfall due to saturated
soils and increased runoff potential. Thus, prolonged periods of
additional rainfall over these regions would trigger a similar
response. The current precipitation forecast suggests larger peaks in
several creeks and rivers than what has been recently observed.
However, high end probabilistic rainfall amounts (i.e. above 90th
percentile) may lead to rivers exceeding action stage to minor
flooding. Most probable basins to see significant rises include; the
Rio Blanco, San Juan, Piedra, Los Pinos/Vallecito Creek, and the
Animas River Basins.

Convective storms and periods of heavy rainfall fed from said
tropical moisture could result in localized flooding impacts across
the CWA. However, confidence decreases rapidly north of the San
Juans. Confidence has increased enough for a Flood Watch to be issued
for southern portions of the forecast area valid from 6AM Monday
through 6AM Wednesday. Continue to monitor the latest forecasts
especially for those who reside and/or plan to recreate in the Watch
areas.

$$

BS