Hydrologic Outlook issued September 25 at 2:21PM MDT by NWS Grand Junction CO

ESFGJT In the wake of today's precipitation, our attention will turn to the Eastern Pacific. Tropical moisture is anticipated to spread across the Desert Southwest early next week, drawing moisture from a pair of Hurricanes; Odalys and Polo. The forecast becomes increasing complex due to a closed low currently forecast to drive across the Southwest CONUS as Hurricane Polo approaches the Baja California Peninsula. Strong southerly winds ahead of the low are expected to pull tropical moisture towards eastern Utah and western Colorado as early as Monday morning. The challenge and uncertainty in our precipitation forecast increase as the week progresses and the low traverses our southern States. Excessive rainfall is most probable over AZ and NM, attm, but the northerly extent poses a threat to our southern San Juan river basins. Current forecasts suggests 1 to 3 inches of rain over Monday morning through Wednesday. At face value, rivers and tributaries will see a bump up due to said moisture. However, localized heavier amounts could result in minor 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 observed over the previous 7 days. 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. Please continue to monitor the forecast as these systems evolve. Especially for those who reside and/or plan to recreate in the southwest quadrant of the forecast area.