This marks the second year that La Niña conditions have developed in the Pacific. Last year, this system brought some of the highest amounts of rain and snowfall recorded for California and other parts of the West. Even though La Niña conditions eased a multi-year drought, they are considered unpredictable (like most long-term weather forecasts). La Niña conditions generally produce colder and wetter weather for the northern U.S., while southern areas are typically warmer and drier.
So what could be some potential impacts of these predictions for 2018? Less than average rainfall could lead to a few things:
- Less growth from native vegetation (particularly grasses) during the winter months. This could lead to increased pressure from summer weeds, due to lack of competition.
- Decreased germination of some weed species. These will usually include winter annual weeds, such as mustards.
- If pre-emergent herbicides sit too long on the soil surface without rainfall, their potential activity may begin to decrease. If the application is timed correctly, the herbicide's effectiveness may be more persistent with less rainfall.
As the winter progresses, more information about rainfall totals will start to paint a more accurate picture about the conditions managers could be facing for the year.
If managed, existing vegetation can used to reduce invasive weed cover