Rain is falling on the deserts and up to a couple of feet of snow will blanket the mountains of the Southwest into Friday night.
The storm that dropped southward across California at midweek with cold rain and mountain snow is turning east to end the week.
The storm continues to bring locally drenching rain to Southern California, as well as near-freezing temperatures with spotty rain and snow to the passes.
Travel along I-40 could be much more difficult for a time at the end of this week with heavy snow, gusty winds and poor visibility forecast for the higher elevations.
According to Western Weather Expert Ken Clark, "The storm will bring a plentiful amount of moisture to the deserts and mountains in the Southwest."
Rain and snow will break out and progress from west to east into Friday from the first storm, before another storm with rain and snow arrives over the weekend.
"In Arizona, from the first storm, the lower elevations will average between 0.25 to 0.50 of an inch of rain with up to an inch possible in lower elevations of the Rim Country," Clark pointed out.
Similar rainfall is expected in New Mexico.
As is often the case any time it rains in the desert and on the intermediate rocky hillsides, there is a risk of flash flooding.
Clark expects snow levels to dip between 5,000 and 5,500 feet with a foot or more of snow possible at elevations above 7,000 feet.
Snow will fall on the upper reaches of the Grand Canyon with this storm. (Photos.com image)
A few inches of snow will fall at elevations above 5,500 feet from Arizona to northern New Mexico.
However, the heaviest snow, perhaps up to a couple of feet, will fall on the mountains in southwestern Colorado.
Perhaps even before the snow from the first storm comes to an end, rain and snow will sweep into the Southwest from a second storm over the weekend.
At this time for the interior Southwest, it appears the second storm will not have as much moisture to work with, so precipitation will tend to be lighter and more spotty in nature.
The region has had a very dry autumn and any rain or snow will be highly welcomed from a hydrological standpoint.
As of Friday morning, the storm has delivered between 1 and 2 inches of rain in the San Diego area with an average of 0.25 to 0.50 of an inch of rain in the Los Angeles Basin.
"Prior to the storm's arrival, since Oct. 1, Phoenix has received only 3 percent of its normal precipitation, Tucson, Ariz. has had only 2 percent and even Flagstaff, Ariz. has picked up only half its normal rain and snow," Clark said.
Phoenix managed to pick up about 0.50 of an inch of rain from the storm Thursday night with about 0.60 of an inch falling on Tuscon.
Meanwhile, about 8 inches of snow has fallen on Flagstaff during Thursday night.
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Dry and sunny conditions will continue in San Francisco for the official start to winter and the Christmas holiday.
Sunshine will return in full force for the weekend, the official start to winter, and Christmas in Los Angeles.
Big changes are on the way for parts of the Western and Central states late this week and into this weekend.
Similar to the days prior to Thanksgiving, the worst weather will focus on the days prior to Christmas as millions of travelers take to the roads and skies in the U.S. and southern Canada.
Warm air is forecast to surge into much of the eastern half of the nation by the weekend and will be accompanied by heavy rain and flooding risk in some locations.
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12.5" snow, max. 24 hour December snow.
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282 straight days without subfreezing temperatures, longest streak on record.