A vigorous upper level trough digging into the Central and Eastern U.S. has spawned a strong surface cyclone that will continue to impact the eastern third of the nation through early Wednesday.
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Widespread heavy rainfall will likely lead to significant river and flash flooding from the western Carolinas to the Mid-Atlantic and Northeast, and scattered to numerous flash floods will be possible.
The highest flash flood chances are over the far western Carolinas and from northern/central Virginia through southern New York and into Connecticut to Rhode Island where there is a Moderate Risk of Excessive Rainfall.
The tight pressure gradient accompanying this system will also produce an expansive area of high winds, and there are widespread Wind Advisories and High Wind Warnings in effect from the middle/lower Mississippi to the Southeast and up the East Coast.
Strong winds with gusts in excess of 55 mph are likely to cause numerous power outages and moderate to major coastal flooding in the Mid-Atlantic and New England.
Severe thunderstorms will also be a hazard for the Southeast with a powerful mid-level jet in place ahead of the cold front.
The Storm Prediction Center has highlighted this region with an Enhanced Risk for severe thunderstorms through tonight, and storm hazards may include tornadoes (some strong), damaging to severe wind gusts, and isolated hail.
Additionally, wintry precipitation on the northern and western sides of the system will create hazardous conditions for parts of the Midwest and Great Lakes.
Heavy snow bands with rates of 1-2 inches per hour will shift from the Upper Midwest this afternoon into the Great Lakes tonight.
These snow rates will be accompanied by gusty winds reaching 30-40 mph, making for dangerous travel due to low visibility and snow covered roads.
An additional 4-8 inches of storm-total snowfall is possible from the western shores of Lake Michigan to the Upper Peninsula of Michigan.
Heavy/wet snow will move across the high terrain of the interior Northeast tonight into Wednesday.
This snow will cling to trees and power lines, which when combined with gusty winds potentially exceeding 55 mph, could result in power outages and scattered tree damage.
Conditions will gradually improve on Wednesday as the system moves out, although precipitation and strong winds will linger into the afternoon for the Northeast.
A weaker low pressure system will approach the Upper Midwest and Great Lakes region on Wednesday into Thursday morning, but it will not have much moisture to work with, so mainly light snow is expected with that event.
Meanwhile, conditions will be deteriorating in the West as a series of frontal systems push southeast across the region.
Blizzard conditions will continue through Wednesday morning in the Northwest, bringing snow totals to several feet in the higher elevations of the Cascades and Olympics with wind gusts in excess of 60 mph.
Snow levels will fall to 1000-2000 feet on Wednesday, leading to considerable travel impacts for many mountain passes.
Heavy snow exceeding 12 inches is likely for many of the other higher elevation mountain ranges of the West, including the Northern Rockies, Sierra Nevada, and Wasatch.
In the Great Basin, snow squalls are likely through Wednesday.
Intense bursts of snow of 1-2 inches per hour and wind gusts over 50 MPH will lead to rapid changes in visibility, occasional whiteouts, and pose significant danger to motorists.
The storm will emerge into the Plains by Thursday and strengthen.
A swath of heavy snow is likely somewhere in the Plains and Midwest by Friday and Saturday.
Blowing snow will also be possible in strong winds.
Colder temperatures will plunge into the Central U.S. in the wake of a cold frontal passage this week, initially impacting the northern Rockies and northern Plains on Wednesday and expanding into the central Plains by Thursday.
High temperatures will likely stay in the negative digits or only reach the single digits in the northern Rockies and northern Plains Thursday and Friday while the central Plains only reach the teens.
Wind chills will be even lower, reaching as low as 25-35 below zero in parts of Montana where Wind Chill Advisories are already in effect for Wednesday and Thursday.
Frostbite and hypothermia will be a concern if precautions are not taken, and dangerously cold wind chills could cause frostbite on exposed skin in as little as 10 minutes. ■