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Planting conditions improve over much of US West thanks to heavy snowpack, rains

The way that the West is (largely) winning the battle of the drought is staggering, climatology experts agreed during the 2023 Western Drought Webinar May 9. Extremely heavy snowfall this past winter was followed by unusually cold spring temperatures which stopped the threat of large-scale flooding. Conditions weren’t perfect everywhere though. While substantial improvements have been made in drought conditions across most of the western U.S., smaller areas of drought continue in eastern Colorado, New Mexico, central Utah and southern Nevada. Also, an area of flooding has been impactful near Salt Lake City, Utah. 

DROUGHT SOMEWHAT DIMINISHED

The key message from this webinar is that the heavy western snowfall this past winter has ameliorated drought conditions across much of the western U.S., although it will take more than one drought-busting year to shore-up reservoirs. The main improvement is, At the beginning of the water year, over 96% of the west had some sort of drought category from abnormally dry to exceptional drought. And, almost 20% of that western area was in the extreme to exceptional drought — areas in red shades. Now, only half of the west is in some drought stage, with only 1% in extreme to exceptional drought, showing an extreme lessening of the drought,” said Joseph Casola, director of the Western Region-Regional Climate Services at NOAA’s National Centers for Environmental Information, who was a speaker on the hour and an half webinar. 



Weather-RFP-051523

COLD SPRING PREVENTS SOME FLOODING

Multiple “atmospheric river events” brought frequent precipitation, and the snow events produced 150% of the average. Many have been intently watching and bracing for potential flooding. While there has been flooding in the West and there will be future flooding, the unusually cold temperatures this spring have been a saving grace. “Colder than normal temperatures across the region really helped to hold the record snowpack up at the higher elevations. Typically, we start seeing lower elevation snowpack melt in March, but this year we didn’t see any melt in March. We actually saw more and more snow accumulation in March,” said Paul Miller, service coordination hydrologist at NOAA NWS Colorado Basin River Forecast Center, one of 13 River Forecast Centers across the U.S. Comparing this out-of-the-ordinary snowpack to last year’s historically dry January and February is huge, the experts agreed. The most impressive aspect this year has been how consistent the snow accumulation was and continued accumulating through the first week of April. Only recently, has the snowmelt begun in earnest. There was a little warm-up, then a cool down then more warming, and not we’re starting to see some of these flows making it into reservoirs, said Miller, who also spoke on the webinar. “I think this is even more striking than the precipitation. With climate warming, the odds for such a long-lived anomaly of cold over a large area like the west, the odds for that go down, so it’s a very surprising situation,” Casola said. When we have relatively cold and wet conditions, that sets up a really good situation for snowpack, he added. 



CHALLENGES IN SOME AREAS

While most of the snowmelt hasn’t occurred yet because of the unusually cool spring temperatures, there has been significant flooding in the Great Basin near Salt Lake City, Utah. “The biggest impact has been agricultural fields that have flooded, and livestock has been lost in northern Utah and southern Idahol, near the Bear River. Some homes saw basement flooding in the greater Salt Lake City area,” Miller said. Impacts are mostly localized, and aren’t widespread, he added. Arrival of a lot of snow or rain in a short period of time can cause devastating consequences, such as the communities displaced in California, which also had loss of life and significant damage, Casola said. Miller noted they have a lot of space in reservoirs to store the water, but that flows are going to be above-average everywhere. “So, people need to be aware of this. With warmer temperatures beginning recently in May, increased snowmelt and increased stream-flows will occur throughout the West. Most of the melting hasn’t started yet, because there have been cooler temperatures in March and April,” Miller said. Different challenges include eastern Colorado and eastern New Mexico that that didn’t get quite the precipitation that other parts of the Rockies and the Sierras received. Further north in Montana and northern Idaho, snowpack was still close to the 30-year median value, but not quite as abundant as locations further south.

WET, SNOWY WINTER EFFECTS

The wet, snowy and cold winter has also provided good soil moisture. As of April 1, the record-high snow water equivalent (SWE) indicated above-average snowpack in western Colorado, Utah, Nevada and California, which means good reservoir storage. Where water is currently, the stream-flow is abundant. Soil moisture also helps determine where water is located, especially in the top several feet which usually gets down to the root zone. That indicates relatively high soil moisture.

LAKES POWELL AND MEAD

Water at reservoir level is over 100% of the average in California. The Colorado River Basin has close to its capacity, however there are two exceptions, Lake Powell and Lake Mead, which are the biggest reservoirs. Lake Powell is the gateway between the Upper and Lower Basins. Lake Mead is just below that, and currently they are still quite low. Although the forecast calls for their levels to increase, they are however, still reflecting multiple years of dry conditions, and decades of low levels. “It would take six to eight consecutive years of this kind of winter to refill reservoirs in the Upper Colorado River Basin and bust the past 20-year deficit and drought,” Miller said. There’s not a lot of dedicated aquifer storage space throughout the Upper Colorado River Basin, but climate managers make forecast decisions daily to more efficiently manage resources. They decide whether to move water into diversion canals or store as much water as possible in the current reservoir system, Miller said.

“I think the biggest issue is we don’t manage. We have more resources dedicated to emergency responses, but we could all think about long-term environmental changes, largely driven by climate change,” Casola said.

Experts agree, the last 20 years have been a fascinating case study for them and there’s a lot to learn about our climate system.

With La Nina dominating this year’s forecast, conditions were typically expected to favor below-normal precipitation for the southern tier of the U.S., but another sub-seasonal climate phenomenon, the Madden Julian Oscillation impact was much larger than La Nina. “You can’t predict MJO (Madden Julian) beyond two weeks. If possible, we need to extend the skill of predicting it, because it’d be very beneficial for seasonal precipitation for the southwest U.S.,” said David Dewitt, director of NOAA’s Climate Prediction Center, also a speaker on the webinar.

EL NINO’s ARRIVAL

El Nino (the opposite of La Nina) is predicted to occur this summer with a 60% probability, and increase to 80% by fall. An El-Nino Watch has been issued. El Nino’s impacts on U.S. precipitation in summer are small. The webinar was hosted by several NOAA partners of the National Oceanic Atmospheric Administration, including the National Integrated Drought Information System, Climate Prediction Center, NWS Colorado Basin River Forecast Center, and NOAA’s Physical Sciences Laboratory, also the U.S. Geological Survey.

For more information, go to http://go.usa.gov/3eZ73.

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