By Allison Chinchar, CNN Meteorologist
Back-to-back-to-back systems will make their way across the United States over the next few days, with the last — and largest — storm bringing heavy rain, blizzard conditions and the potential for tornadoes.
While wintry weather is spreading into the Plains Thursday and will push into the upper Midwest on Friday, a cold front will begin to impact the Pacific Northwest and is expected to bring up to 2 inches of rainfall along the coast. Over a foot of snow is expected across the Sierra Nevada Mountain Range. The storm will begin to impact the Pacific Northwest Friday evening, bringing additional threats this weekend and into next week.
Quick shot of snow and ice through the Plains and Midwest
The current storm tracking across the Plains and Midwest will bring a variety of winter weather from the Rockies to the Great Lakes through Friday. Over 7 million people are under winter weather advisories, as a band of snow and ice will lead to travel difficulties across numerous states.
Cities like Sioux Falls, South Dakota, Minneapolis, Madison, Wisconsin, and Milwaukee will deal with gusty winds and blowing snow. While in Omaha and Lincoln, Nebraska, freezing rain will be the main concern.
Along the southern and central San Juan Mountains in Colorado, the new heavy snow is leading to avalanche watches and warnings.
“This particular area has a very unstable snowpack, so be careful if you are traveling through the backcountry,” CNN Meteorologist Derek Van Dam said Thursday.
For southern states, the main concern is rain. From the Ozarks to the southern Appalachian Mountains, 1 to 3 inches of rain is expected through Friday. This is on top of widespread 2 to 4 inches of rain that has already fallen since Monday.
This means the ground is saturated in a lot of areas and will be more prone to flooding as additional rain moves in.
Round of snow and rain ahead of main event
For the Pacific Northwest, the recent pattern of rain and snow is expected to stay through the weekend. On Thursday, a new storm system will head across the West, where winter weather advisories are in effect across four states.
Over half a foot of snowfall is possible across the alerted areas in northern Idaho, western Washington and Oregon.
“More heavy precipitation expected for the Pacific Northwest and northern California today before the next round arriving by Friday night,” the Weather Prediction Center said on Thursday.
Along the coast, heavy rainfall and gusty winds will hammer the area with 1 to 2 inches of rainfall expected through Friday … before the main event arrives.
Flash flooding, blizzard conditions and tornadoes possible next week
A blockbuster storm looks to be taking shape in the West for this weekend into early next week, threatening flash flooding, blizzard conditions and tornadoes.
This storm will begin to impact the Pacific Northwest by Friday evening and will spread to California throughout the weekend. Periods of coastal rain and heavy mountain snow are forecast for the Cascades.
Winter storm watches are in effect along the Sierra Nevada Mountain Range, where some isolated locations could see snowfall totals up to 5 feet through the weekend.
Snowpack, which is off to a robust start with some places already 200% of normal for this early in the season, will also benefit from the additional moisture this next storm system will bring.
“Clearly the snow totals are the headline, but the extreme wind along with the snow will cause significant power outages and roads drifting shut,” said Chad Myers, a CNN meteorologist. “Travel will be nearly impossible at times. Getting stranded in your vehicle will be very dangerous.”
Coastal rain could reach 6 inches in parts of northwestern California, bringing significant relief to the drought conditions. While the precipitation is welcomed, too much rainfall too quickly could lead to flash flooding and landslides.
“Very heavy rainfall will occur at lower elevations along the coastal areas with flash flooding and mudslides possible from just north of San Francisco to Seattle,” Myers said.
New threats will emerge early next week as that storm progresses eastward into the central US.
“As the system moves into the Plains early next week, a spring-like storm system develops,” Myers said. “Significant severe weather will occur in the warm air across the South and a major snow and ice event happens in the western Great Lakes and northern Plains.”
For the northern Plains and Midwest, the threat for blizzard conditions is increasing. Significant snow, strong winds and ice and freezing rain will all be possible early next week.
That threat is also increasing across the southern Plains and Gulf Coast region.
“Severe risk is expected to gradually increase, from negligible at best [Sunday], to increasing over the Oklahoma vicinity Monday, and through what is expected to be substantial potential [Tuesday] from eastern portions of the southern Plains to the Lower Mississippi Valley,” the Storm Prediction Center said Thursday.
Tuesday is six days out. But the storm center currently has a 30% probability area of concern for Day 6 — the first time they have issued this in over four years and the first to ever occur in December.
“The details regarding the areas most at risk from tornadoes will become clearer as the event approaches and smaller-scale trends become more evident,” Matthew Elliott, a meteorologist at the Storm Prediction Center, told CNN. Damaging winds and large hail will also be of concern.
“While tornadoes in December are relatively uncommon when compared to the springtime, they are often more likely across portions of the Southeast and Lower Mississippi Valley, where there is often a secondary peak in the fall and winter,” Elliott said.
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CNN meteorologist Monica Garrett contributed to this article.