Winter weather across the northern US could mean hazardous holiday travel, while record-breaking springlike temperatures warm the south
CNN
Jack Frost is taking over the northern US for the holiday weekend, delivering heavy snowfall, plummeting temperatures, and a white Christmas to the Pacific Northwest. The northern cold stops short of the southern US, where balmy springlike temperatures will likely break records.
An atmospheric river event along the West Coast is packing moisture into the region, forcing those in the Northwest to break out the shovels.
Frightful winter weather
Millions of people are under winter weather alerts spanning the western US this holiday weekend.
Two rounds of storms will batter the West Coast, creating hazardous travel conditions.
In the initial round of storms pushing through Friday, heavy snowfall will mainly be confined to the higher elevation regions of the Sierra, Cascades and Rockies.
Snow totals surpassing a foot are expected across the region.
A second system of storms moving in Friday evening will cause more problems for the West, bearing heavy mountain snow and rainfall to the lower elevations — alongside flash flood threats and dangerous travel conditions.
“Travel will be be hazardous, even impassable at times, in the hardest hit locations with towering snow drifts and whiteout conditions,” the NOAA Weather Prediction Center said Friday.
Six to eight feet of snow are possible through the holiday weekend in the Sierra, with localized areas potentially blanketed under ten feet of snowfall.
Flood threat
Southern California will also experience the effects of the atmospheric river Christmas Eve. The storm systems will drench the region in flooding rainfall.
Atmospheric rivers are flows of moisture thousands of feet in the sky. They tend to be 250 to 375 miles wide and are said to transport an amount of water vapor equivalent to 7.5 to 15 times the average flow of water at the mouth of the Mississippi River.
Flash flood watches in southern California cover over 10 million people, including San Diego, Anaheim, San Bernadino, and Palm Springs through the weekend.
Areas under watches also include parts of northwestern Arizona where the Flag Burn Area is susceptible to debris flows.
Heavy rainfall in the region is already causing reports of landslides blocking roadways during one of the busiest travel weekends of the year, according to the San Diego National Weather Service.
Hopeful for a White Christmas
Places that scarcely see a true White Christmas might just get what’s on their wish list this year.
Arctic air pressing into the Pacific Northwest and interacting with the atmospheric river event is expected to lower snow levels near to sea level.
Coastal cities like Seattle and Portland could see snowfall as storms ramp up into the evening on Christmas day.
Check your climatological chance of a white Christmas
In Portland two to four inches of snow is forecast to fall, while Seattle has a much lower chance for lingering snowfall.
“Warm ground temperatures combined with temperatures above freezing will make it hard for snow to not melt quickly after any brief accumulations and some locations may just see a cold rain,” the NWS in Seattle said.
Seattle has only seen measurable snow on Christmas Day 9 times in 127 years of record.
The Governor of Oregon has declared a State of Emergency until January 3rd due to the potential for hazardous winter weather conditions and sustained sub-freezing temperatures.
Temperatures will drop significantly through the weekend, with more snow and highs near freezing by the beginning of next week.
Travel woes in the Northeast
Across the country another storm system is pushing into the Great Lakes region providing seasonal winter weather to the Northeast.
The same system brought freezing conditions and hazardous driving to the Midwest on Thursday, leading to interstate crashes and delays.
Winter weather advisories are in place for cities across the Northeast, including Boston, where ice accumulation could lead to dangerous Christmas weekend travel.
Snowfall is forecast to become more widespread across New England over the course of Christmas day.
Bah Humbug record highs
While many will see a rare White Christmas, a large portion of the country will experience mild weather Saturday.
From Texas through the southeast, it will feel less like December and more like springtime.
Temperatures 20 to 30 degrees above average will make a run for daily high temperature records, and may even break records for the entire month of December according to the WPC.
Along with the warm temperatures, level 2 of 3 critical fire danger has been issued by the Storm Prediction Center for parts of West Texas on Friday.
Red flag warnings span across parts of New Mexico, Texas and Oklahoma where 30 mile per hour sustained winds and dry conditions could easily lead to wildfire escalation.
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CNN’s Tyler Maudlin and Judson Jones contributed to this report.
