A significant and disruptive storm system is forecast to produce a multitude of weather hazards over the next several days, as heavy snowfall, strong winds, and dangerously cold temperatures span from the Intermountain West through the Plains, the Great Lakes, and the central Appalachians.
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At the forefront of the active weather pattern is a dangerous and record-breaking cold air mass in the wake of strong arctic cold front diving southward across the central Plains today and the southern Plains by late Thursday.
Behind the front, temperatures across the Intermountain West and northern High Plains have plummeted 25 - 35 degrees F in just a few hours, with widespread minus 10 to minus 20 readings across the region.
This, combined with sustained winds of 20 - 30 mph and higher wind gusts of up to 60 mph, have and will continue to lead to wind chills as low as minus 40 degrees across a large swath of the Intermountain West and northern/central Plains, with more localized areas of minus 50 to minus 70 possible through the end of the week.
Wind chills of this magnitude can cause frostbite in less than 5 minutes if precautions are not taken, with hypothermia and death also possible from prolonged exposure to the cold.
Livestock interests will also be severely impacted and dangers could be exacerbated if power outages occur.
Consequently, widespread Wind Chill Warnings have been issued for areas spanning from eastern Washington State, through the Intermountain West, central/northern Plains, and Tennesse Valley, with additional Wind Chill Watches and Advisories covering areas as far south as the southern Plains and Gulf Coast.
As the arctic front dives southward through the overnight hours and Thursday, daytime temperatures across the central Plains will struggle to get above 0 degrees, while areas further south in Texas and the Gulf Coast will experience temperatures in the single digits and teens Thursday evening.
Furthermore, snow squalls, or a brief burst of moderate to heavy snow (1 to 2 hours), are likely to occur immediately behind the arctic front from the Intermountain West, to the central Plains, Ohio Valley, Mid-Atlantic, and Northeast.
Developing snow squalls could lead to extremely hazardous travel conditions at times, as they will be accompanied by gusts to 40 mph, potentially creating sudden whiteout conditions.
Another hazardous facet of the system will be a deepening low-pressure center that forms along the frontal boundary this evening and rapidly strengthens as it tracks eastward across the Midwest and Great Lakes on Thursday.
This storm system is likely to produce widespread light-to-moderate snowfall from the Midwest to the Great Lakes and Interior Northeast, with a brief burst of snow also possible into the Ohio/Tennessee Valleys and northern Mid-Atlantic immediately following the cold frontal passage.
The heaviest snowfall, with amounts potentially exceeding a foot, is anticipated to occur over the Great Lakes between tonight and Friday, especially along westward and northward-facing lakefronts, as lake-enhanced snowfall along with moisture wrapped around the low will help aid in the locally heavy totals.
Combined with the snowfall, very strong winds will also accompany the system as a very tight pressure gradient develops between the low over the Great Lakes and the strong high-pressure system over the northern Plains.
Heavy snowfall rates of 1-2"/hour, along with wind gusts of over 50 mph will result in near-zero visibility and considerable blowing and drifting of snow.
This will lead to dangerous, to at times impossible, land and air travel leading up to the holiday weekend.
The combination of heavy snow and strong wind gusts could lead to significant infrastructure impacts, including scattered tree damage and power outages.
Residents across the aforementioned regions are advised to make final preparations as soon as possible and check on family and friends during the storm in case of an emergency.
Further east, in the warm sector of the strengthening storm system, moisture surging northward ahead of a center of low-pressure and associated coastal boundary situated off the Southeast coast will lead to moderate to heavy rainfall across the Southeast and Mid-Atlantic on Thursday with rainfall totals of 1-3" possible.
As the low-pressure system tracks northward Thursday evening, strong southerly winds ahead of the center of low-pressure, combined with the new moon-tide cycle, may lead to dangerous coastal flooding from northern New Jersey to northeast Massachusetts.
Furthermore, heavy rain over a fresh snowpack could also create scattered flooding concerns for parts of Vermont and Maine on Friday, which has prompted a Slight Risk (level 2/4) of Excessive Rainfall to be issued.
Lastly, at the leading edge of the northward surging moisture over the Mid-Atlantic during the first half of the day on Thursday, light freezing rain and locally heavy snowfall could impact parts of the central Appalachians.
A lingering cold air damming environment will likely keep this brief punch of wintry weather confined to the higher terrain and near the Blue Ridge mountains, but could still lead to snowfall totals of up to six inches in some spots.
Moreover, on Friday, as the arctic cold front races eastward across the Mid-Atlantic and Northeast, temperatures will plunge from the mid-to-upper 50s to the 10s and 20s in a matter of hours, which could lead to a rapid flash freeze of wet pavement and surfaces from antecedent rainfall.
Looking forward, the next storm system to impact the Pacific Northwest will spread precipitation and gusty winds onshore by late Thursday ahead of an approaching warm front.
After initially starting as snow, sleet and freezing rain is likely to develop and could linger for an extended amount of time over parts of western Washington and northwestern Oregon.
This changeover to freezing rain is due to a dense arctic airmass remaining in place at the surface while warmer air surges over the region in the upper levels.
Localized ice accretion of a half inch could create the potential for dangerous travel conditions and scattered power outages. ■