Chris Dolce
Serious drought conditions continue in the Southwest, and while some beneficial rain and mountain snow are in the near-term forecast, the expectation of La Niña this winter could be bad news for the region.
Extreme and exceptional drought - the two worst categories on the U.S. Drought monitor - are widespread across the Southwest, from West Texas to Nevada and Arizona.
The U.S. Drought monitor update for Oct. 22 shows that extreme or exceptional drought covers well over half of five states, including Utah (87%), Arizona (84%), Colorado (77%), New Mexico (67%) and Nevada (58%).
The Colorado River basin is facing its most expansive level of exceptional drought (20.3%) in 18 years, NOAA's National Integrated Drought Information System said Thursday. That's important since more than 30 million people are provided water by the Colorado River and its tributaries, according to the United States Geological Survey.
Drought in the Southwest intensified this summer and early fall after the monsoon failed to provide any significant bouts of rainfall to the region.
This monsoon is relied upon to reduce the risk of wildfires and brings much-needed rain to the region for reservoir replenishment and vegetation. Most of northwestern Mexico and the southwestern U.S. receive over half of their annual precipitation from the monsoon.
Forecast: Some Relief Ahead
The good news is that some beneficial moisture is finally in the forecast early next week.
A southward plunge of the jet stream over the West this weekend will bring much colder air and some moisture to the Four Corners region.
We expect this weather pattern to wring out welcome snowfall from Colorado and Utah into parts of northern New Mexico and northern Arizona. This includes areas of northern Colorado, where large wildfires have recently charred hundreds of thousands of acres.
Some light amounts of rainfall could also dampen the deserts of southern Arizona.
Overall, this snow and rain will be a drop in the bucket when it comes to improving drought conditions, but it should at least tamp down wildfire danger in some areas.
Winter: What La Niña Means
La Niña conditions in the equatorial Pacific Ocean are expected to influence weather patterns in North America as we head into winter.
Unfortunately, that could be a bad thing for the Southwest.
In typical La Niña winters, the overall jet stream pattern arcs northward along the West Coast. That means moisture-laden Pacific storms are steered into the Northwest, and less frequently the Southwest.
As a result, drier than average conditions are typical in winter during La Niña in the Southwest, as depicted in the map below. This doesn't mean it will be nearly-bone dry like it was over the summer, but the overall intake of rain and mountain snow could be less than average for winter.
NOAA's winter outlook released last week reflects the La Niña influence, with odds tilted toward below-average precipitation across all of the Southwest this winter.
That said, La Niña is only one factor that can influence the large-scale weather pattern in winter. There can be other overriding atmospheric influences for periods of time that lead to a different outcome than what is typically expected in La Niña winters.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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