Hydrologic Outlook

ESFGJTStrong 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.