Early-Season Heatwave Poses Severe Threat to Western US
States across the western United States are preparing for a brutal early-season heatwave that threatens to bake multiple cities through the weekend and into next week. Forecasters have issued warnings that temperatures will spike 20 to 30 degrees Fahrenheit above normal levels for several consecutive days, creating hazardous conditions.
Potential for Historic Temperature Records
Daily records could be shattered in southern California this week, according to the National Weather Service, with a possibility that all-time records for March will also be broken. Following the warmest winter on record across most of the region, these intense conditions are expected to further reduce low snowpack levels, intensifying drought concerns.
Caused by a large and persistent dome of high pressure settling over a vast area of the west, the heat blasts are anticipated to arrive in two distinct waves. The first wave will impact the west coast on Thursday, spreading eastward through California, Nevada, Arizona, and New Mexico. A second, stronger round is scheduled to begin on Monday, extending into Utah, Colorado, Oregon, Idaho, and Wyoming.
Public Health Risks and Widespread Impact
By Tuesday next week, areas home to approximately 26.4 million people will be affected by moderate heat risks, the second level out of four designated by the National Weather Service. This level particularly endangers sensitive populations and those without access to cooling or adequate hydration. Tens of thousands may face extreme heat, the highest risk level, with no relief overnight.
Extreme heat occurring so early in the year could pose heightened public health dangers. "This time of year, the body isn't used to dealing with this level of heat, so these highs are more impactful now than they would be in July," National Weather Service meteorologists in the San Francisco Bay Area cautioned in a Thursday social media post.
Expert Warnings and Climate Implications
"The next 10-14 days look truly exceptional across the western US, and not in a good way," climate scientist Daniel Swain remarked about the event on Wednesday. He indicated that a ridge of high pressure, among the strongest ever observed in the south-western US in March, is expected to develop by Friday. However, its records are unlikely to hold for long, as it "reorganizes into an even broader and stronger ridge next week."
With a high likelihood of historic heat for early spring, some records might be broken for seven to ten days consecutively, Swain added. Temperatures could climb past 100 degrees Fahrenheit (37.8 degrees Celsius) in Los Angeles, reach up to 90 degrees Fahrenheit (32.2 degrees Celsius) in the San Francisco Bay Area, and possibly soar to 110 degrees Fahrenheit (43.3 degrees Celsius) in the south-eastern deserts, thrusting the region into summer-like conditions months ahead of schedule.
Environmental and Resource Concerns
The heatwave coincides with water managers across the west anxiously monitoring declining snowpacks, which are expected to shrink further. Hopes for another cold storm to replenish the depleted snow, crucial for water supplies during warmer months, are fading. Heat also extracts more moisture from landscapes, amplifying wildfire risks and extending the seasons when ignitions can rapidly escalate into infernos.
"During the upcoming period of exceptional and prolonged heat–which will bring t-shirt and shorts weather even into the higher mountains of the American West–snowmelt will accelerate dramatically," Swain stated. The spring snowpack, measured on April 1, "may well be the worst on record across many, if not most, western US watersheds."
