CNN
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Hurricane Hilary is expected to intensify into a lashing Category 4 storm as it nears Mexico’s Baja Peninsula on Friday and then weaken over the weekend, bringing rain and flooding to parts of the Southwest US.
Hilary was churning about 430 miles south of Cabo San Lucas, Mexico, Thursday night with sustained winds of near 125 mph, the National Hurricane Center said in an overnight advisory.
The storm strengthened to a Category 3 hurricane Thursday evening and is likely to build into a powerful Category 4 on Friday, the advisory said. It is then expected to begin weakening as it continues north on Saturday.
Hilary’s center is on track to approach the Baja Peninsula on Friday and over the weekend, prompting Mexican officials to issue a hurricane watch and tropical storm watches and warnings for parts of Baja California Sur, the hurricane center said.
There remains a wide range of outcomes for the heaviest rain and strongest winds in the US as the storm moves north over the next couple of days along Mexico’s Baja Peninsula. Small deviations in the hurricane’s track could change the forecast for the most intense rain and wind.
“The threat of significant wind impacts continues to increase for northern portions of the Baja California Peninsula and the Southwestern United States, especially in areas of mountainous terrain,” the hurricane center said Thursday night.
Flash flooding and mudslides may also be triggered by downpours in parts of the peninsula from late Friday into Sunday.
Hilary is expected to substantially weaken before reaching Southern California and parts of the Southwest but there’s an increasing chance the regions will be significantly impacted by heavy rain and flooding.
Heavy rainfall is expected to begin impacting the Southwest on Friday and through early next week, with the most intense downpours likely on Sunday and Monday, according to forecasters.
Southern swaths of California and Nevada could see 3 to 5 inches of rain with isolated amounts of up to 10 inches. Smaller amounts of 1 to 3 inches are expected across central parts of those states as well as across western Arizona and southwest Utah.
Prolonged rain may oversaturate the ground and overwhelm waterways, potentially worsening the flood threat.
Weekend flood watches have been issued across southern California stretching from San Diego to Los Angeles as residents brace for potential deluges.
The National Weather Service in Los Angeles has also warned of the potential for dangerously high surf, rip currents and coastal flooding.
If Hilary makes landfall in California as a tropical storm, it will be a rare occurrence – the first such storm there in nearly 84 years and would be only the third tropical storm or stronger to do so on record, according to data from the National Oceanic and Atmospheric Administration.
As the rainfall passes through the Southwest, it may help combat prolonged drought and recharge depleted groundwater.
Drought conditions persisted in California and Arizona this week and expanded in New Mexico, the US Drought Monitor reported Thursday.
Thanks to Hilary, “multiple years’ worth of precipitation could potentially fall in some of the driest parts of California,” Daniel Swain, a climate scientist at the University of California at Los Angeles, said Wednesday.
Among those spots is Death Valley, California, the hottest place on Earth. Death Valley typically receives about 2 inches of rain across an entire year, according to NWS data. Moisture from Hilary could unleash enough rain to give Death Valley at least a year’s worth of rainfall in a single day.
But the deluge could also prove dangerous. Around 1,000 people became stranded in Death Valley National Park last August when 1.46 inches of rain fell in 24 hours, triggering flash flooding that wiped out roads and entombed cars in floodwater-swept debris.
The region has also suffered from the absence of a seasonal monsoon that supplies a large percentage of its yearly rainfall, leaving cities like Phoenix desperate for more rainfall as they endure weeks of sweltering temperatures.
Now, the region is expected to get some relief from the extreme heat as the combined rainfall and increased cloud cover could lower triple-digit temperatures by as much as 20 degrees. The cooling may even help Phoenix break its dangerous heat streak by bringing temperatures below 100 degrees for the first time since mid-June.
